Heating Help

Infloor Radiant Heat issue

Hello.  We just recently purchased a property that has this system in the concrete slab.  The cottage is under 1000 sq ft and has 2 loops in the floor with an Electromate electric boiler.  The problem we are having is that the system can't maintain the set temp of 68 or 69 once it gets dark at night.  The temp will drop 6 - 8 degrees and won't catch back up until late AM the next day.  Of course we realize that it takes the system sometime to heat up from the 55 degree setting we keep it at when we are not there.  We have found a solution to this situation as a neighbor is going to turn the heat up 10 - 12 hours before our arrival.  But the 3 times we spent there thus far, the system will be right on at the set temp during the day but drops at night. 
We have a vaulted ceiling which is 23 ft in height.  One half of the cottage has a loft above.  We also have 3 windows side by side on both the northwest  and northeast corner as well as 6 windows (3 on each side) on the north side.  These are quality Andersen double pane units.  This property was completed in 2009 by the former owner.  We understand from the builder that their is R19 insulation in the ceiling. 
We had a local plumbing/heating contractor recommended by our realtor in to inspect the system.  We had to do this via phone and help from our realtor as we are 275 miles away.  The contractor indicated that the system seemed to be working as it should and seemed to be sized adequately for the square footage.  He spoke with a contact at the local electric provider to find out what setup for usage we were at...restricted or unrestricted.  We have no restrictions and, of course, are paying the higher rate for electricity as we don't have a dual fuel source.  His recommendation was to install a gas wall heater to assist the radiant heat in keeping up.  His opinion was that even though the system was adequate for the square footage.  It didn't account for the vaulted ceiling, loft area, windows, and lower insulation value of this type of ceiling.  His recommendation with the gas heat was to enable us to have a lower electric rate for our heat to bring the electric costs down. 
I believe that is one option.  However, it doesn't address the inefficiency or inabilility of the current radiant system keeping up with the demand.  I'm not sure I want to spend the $2000 - 2500 to install this gas heat, tank, and meter/electric hookup to see how this will work.  There is also the unknown as to how much gas we will be using to supplement the system.  The other issue is the space for the gas heater.
I realize that I don't have a lot of info regarding the current system but plan to find out the boiler size and take pictures if necessary.  I've talked to various contractors, company reps, and other owners of radiant heat systems.  I guess there are just too many variables to give different views on the problem.  We plan on talking with the builder and hopefully the cement contractor to see if the slab was insulated properly.  I've been told that you would be able to see heat loss around the foundation if it wasn't insulated on the sides and also the reverse.   That the heat would go down into the ground??  I also do not see any snow melting off the roof of the property so it must be fairly well insulated.
Anyway, in closing, I would appreciate any help, suggestions, things to check for, or other advise you might have.
Thank you!

Need lots more information...

Need boiler model/size.

Need pump size.

Need actual square footage served.

A heat loss calculation should have been performed by someone. Check with the GC and see if you can get a copy of it.

It might also be a good idea to have a blower door test performed on the dwelling to see if there are a lot of air leakage issues.

Some boiler room photographs would be helpful as well, showing the near boiler
piping.

As far as slow reaction is concerned, there are numerous devices on the market that will allow you to call your house and turn the system up before you get there. It will also call you if the homes interior drops below a certain adjustable temperature.

Get back to us.

ME

dwelling location

 I'm not a professional as Mark is, but just some thoughts.

With key words like cottage, 1000 sf, loft, and expansive north facing glass which is not ideal to have. Would this be a lake/river view property, or some type of mountain view location?
 
   If so could it have been built as a summer occupancy only property with a heating system designed to get through shoulder heating months only to be closed up for dead of winter retreat?
 
 Does the heating system contain a glycol mixture instead of straight water?
 
 
 Is the 1000 sf including the loft? If so how many radiant sf on the main floor.
 
 What size (diameter) is the tubing supplying the slab?
 
 Btu output of electric boiler?
 
 Floor coverings what kind?
 
 
 The two loops need be figured out for spacing to the sf of main floor. With only two could be wide center spacing, really long loops with close spacing, or smaller sf covered then I'm thinking. Right now guessing 250sf loft 750sf main floor.
 
 If dimensions are as I think that is two loops at 375' each with 1' spacing, or 15" spacing at 300' each loop. 
 
 Trying to get in the system designers head is part of the task.
 
Gordy

Heat Issue

Thank you for the quick response to my issue.  I'm heading up there this weekend so will try to obtain the info requested.  The floor covering is ceramic tile.  At this point, it is a weekend/vacation home.  The original owner built to use in all seasons.  Unfortunately, the heating contractor is no longer in the area so can't go to him for any info.  I also forgot to mention that I believe the thermostat is a standard air temp unit.  I've read where a person should use slab thermostats for this type of heat??
Thank you!

heat issue

Sorry....forgot to mention that this property is not on a lake......a 1/4 mile from the lake.  It is in the woods so wind isn't as big an issue as say where my permanent home is in South Dakota!  The location is in N Minnesota so temps can get rather cold.

Thats a start

 Ceramic tile is radiant friendly so no high r value floor coverings is a plus. Being sheltered in the woods good also.  So I can assume the north facing glass is do to lot orientation.  Are you sure the R 19 insulation is not the walls instead of the roof?
Even though its cathedral you should be able to get at least an r 30-38 in the roof. R 19 in the roof is not much for northern MN. If he designed for year around occupancy.

 Double check to see if the slab at least has perimeter insulation installed you should be able to visually see that. It may be covered with a skirting material.

Gordy

In floor radiant...

I have that too; copper tubes in a concrete slab. One thing to be aware of is that if you change your set point, it takes 3 to 6 hours (YMMV) to notice the effect, and 12 to 24 hours for the system to re-stabilize, due to the high thermal mass of the slab. So I hope your system has outdoor reset and that it can be adjusted properly.

One reason for using outdoor reset is so that as the outdoor temperature drops, the water temperature in the slab can be increased even before your house gets too cold. Of course if your boiler is already going at its maximum, outdoor reset will not get any more out of it. And you will probably not want to put more than 120F water into the slab anyway. For this to be most helpful, it helps if you adjust the reset curve so the circulator runs a lot of the time; e.g., 12 to 18 hours a day. Some people advocate 24 hours a day, but I do not do that. But I am not a professional, so I have experience only with my own boiler. For my system, doing setbacks in the zone heated by the slab does not make sense except for vacations when I will not be here because the recovery time is so long. Before I thought about it, I had to start the night setback around lunch time, and the recovery for the next day around 10 PM. Even that was not satisfactory because the outdoor temperature does not change the same every day, and if the inside temperature does not drop enough, the boiler and circulators do not run. I do a little setback in my upstairs (baseboard) zone, but even there, I do only 2F of setback and it takes quite a while to recover since I use low water temperatures in the baseboard.

About having a neighbor turning on the heat before you get there. It is probably a good idea to have that done the day before you get there. I have an alternative, a thermostat that can do a setback for up to 255 days and at the end of the setback it will turn on the heat in the morning, daytime, evening, or night. It is a Honeywell CT3600; However it is discontinued. It looks as though a VisionPRO 8000 7-Day Programmable Thermostat will do this.

Good points

 JDB, But they are reaching setpoint during the day, and losing it over night.  And they are bringing the slab up from a 55* set point. Not a real cold start up but if the system is border line to the load its a chug. We do not know conditions as far as outdoor temps, how long occupied while the problem is occuring.

 IF no insulation under slab then there is a heat sink issue to overcome. No perimeter insulation heat sink just got bigger.

Gordy

Two different issues.

I think we all lack sufficient information about the system in question. Heat loss? Amount of radiation, insulation, presense or absense of reset an how it is adjusted if present, etc.

There seem to be two issues.

1.) Time to recover from long setback to 55F. With a concrete slab, at least like mine, that would take over 24 hours to recover. Once my old boiler quit sometime late Friday or Saturday and they did not come to fix it until Monday morning. My house is quite well insulated, so the temperature did not become objectionable unitl Sunday night, and I resorted to sweaters and an extra blanket at night. Once the problem was fixed, heat started, but it was not until sometime during the day Tuesday that things were back to normal. That boiler burned 70,000 BTU/hr and my heat loss is less than 35,000 BTU/hr, so I definitely had enough heating capacity, but I did not wish to turn up the water temperature and burn my feet. About the only solution I can think of is to turn on the heat a day or so before he comes home, either by having a friend do it, or by getting a fancy thermostat to do it.

2.) If he has barely enough boiler, or barely enough radiation, so he can maintain the setpoint during the day but not at night, we cannot escape the need for the heat loss study results. It may be hopeless with the current system (without changes). If it is only slightly marginal, it might be that he could set up the system to pump most of the time, with the boiler modulated way down, and as it gets colder outside, have the outdoor reset turn up the water temperature to get a head start at warming up the slab for night time.

More Information

Hello.  Just spent the weekend at our place.  I have a correction as far as the make of the boiler.  It is a Thermolec boiler, model B10U-M, which has the capacity to produce 34,120 BTU's.  I'm not sure how we came up with ElectroMate???- possibly the contractor had inadvertently said that brand.  Anyway, we spoke with the contractor on Friday afternoon.  He indicated that there are 3 loops in the slab.  He said the most heat you will ever get out of that system is 27,000 BTU.  It may be sufficient for the square footage based on 8 foot ceilings.  But with the vaulted ceiling, loft, and window area, it is just not enough.  I asked what he would have done had he been the contractor during construction.  He mentioned he probably would have gone with in floor heat in the loft as well which would have required a larger boiler. 
So we are trying to determine our next step to solve our heating issue.  I did take several measurements and I'm going to give the info to our electric coop so they can do a heat loss analysis.   The square footage of the main level is 720 sq ft (24' x 30").  The peak is 23 ft and walls in the open area are 10'8".  This area is around 14' x 24".  So 16' x 24' consists of the kitchen area, utility closet, bedroom and closets, bathroom, and hallway.  This is all under the loft which has a 9 foot ceiling.  The loft area is around 235 square feet.  It has a 10' x 15" area as well as a 6' x14' area which includes the stairway.  The height of the ceiling in the loft is 11' 6". 
I have a difficult time with directions when back in the woods area.  It appears that the home is mostly facing east to southeast.  There are 2 windows on the front side - 1 bedroom and 1 bathroom that are 30" x 58" and front door that is 36" x 80" with 2' x 3' glass area.  The loft has 2 small windows side by side on the front that are 22" x 22".  The backside which would face west to northwest has 2 windows on each side of the fireplace for a total of 4.  They are 34" x 70" each.  On each side in the back corners are 4 windows facing south to southwest and north to northeast for a total of 8.  These are 22" x 70" each.  There is a side door on the north side into a screen porch.  This is a 36" x 80" door with a 2' x 4' glass area.  Above the back windows on each side of the fireplace are 2 windows (total of 4) - a triangle shaped unit that is 30" x 30" x 42" and a trapezoid that is 40" x 32" x 66" x 36".  The fireplace is a 76" wide x 23" tall by 30" deep construction with cultured stone applied.  This is a wood burning unit.  Also the insulation is R38 in the ceiling and R19 in the walls as confirmed by the builder.  He also confirmed that the slab was insulated below the heat tubing as well as around the perimeter of the slab.  I believe that I have everything I could think of in measurements. 
The heating contractor suggested that we do install a slab thermostat so we could use some other source of heat such as the fireplace or infrared heater without have an impact on the thermostat as we would on the current stat.  He agreed with us that we really don't have a lot of room to place a gas wall heater so suggested we look into electric panels for the loft.  We are currently paying $.09 per kwh (raising to $.0943 in April) for electric as we do not have a dual fuel source.  So we would need to look at a gas (propane) supplemental heat to qualify for this rate which is $.0526 (increasing to $.0552 in April).  I did get some pictures of the current system but haven't downloaded them as of yet. 
So, that pretty much lays it out as to what we're dealing with on our heating issue. 
Thanks!

Something's not right...

I come up with around 34 btu/sq ft/hr which should be MORE than enough to keep your home warm. At that rate, you should have floor temperatures of 85 degrees F.

I also disagree with the contractor about the output of the boiler. It appears that he is derating an electric boiler by 20%, which is pure bunk. You don't derate the output o an electric boiler. It is 99.99% efficient.

I'm thinking that you have some elements that are fried, or a contactor that is not pulling in, or a control that is not properly set. Depending upon the R value of floor finishes, the operating temperature of the boiler should be between 110 and 140 degrees F.

You didn't happen to look at the temperature and pressure gage to see what temp it is running did you?

ME

Output

 Mark,

  Could it be he is basing his 27000 btu's by sf output?  720 sf of radiant floor at 35 btus sf is 25200 btus capacity If the floor temps are 85*. So he may be basing on a little higher floor temps.

  But you will lose some of that available output floor minusing kitchen base cabinets closets etc. Even if the tubing were layed out underneath them.

 Another BUT is it is all done right good insulation for structure. Slab is insulated etc. Sounds like good window orientation to capture winter sun, better than north facing.  So the heat loss should not be that much for 1000 sf structure of that type of build. And I do agree that the floor is not meeting its full output potential.

 So I do agree something is not right.  The boiler has the capacity to meet that load.  I also agree some supplemental in the loft area may be helpful. Panel rads maybe. 

 MRT is probably laging with a 12 hour fire up window to get things warmed up could have some effect, but not for long.


  Gordy

Theoretical versus Reality...

I hear what you are saying Gordy, and in a sense you are probably correct. However, the reality of the matter is that it is a well built/insulated home, with a load more likely less than 20 btu/sq ft/hr (except possibly for mega infiltration beyond the end users control) and it is a well know, documented fact that when coming out of a deep set back, that the slab will suck up every BTU thrown at it until things get stabilized.

The reality of the matter is, that the space is dropping considerably at night, and it shouldn't. The daily energy load shouldn't change that much between day and night, except for solar gains. I suspect dead electrical elements in the boiler... There are enough to handle the day time loads, but not enough to carry it through the night.

And you are correct, that the loft could probably use some emitters to increase human comfort in close proximity. The GC was probably going under the impression that radiant heat "Rises". Fiddle faddled by the misguided finger of fate...

When the wood stove is running, convection will kick in, and it's heat WILL rise, probably to the point of discomfort. Shoulda installed a destratification fan...

ME

Agreed Mark

  Would like to see the pics.  One other simplistic question would be where is the thermostat located?  Could it be in a location that could give false ambient readings by day, or night for that matter?  Is it possible that the tstat could be slipping in to a set back setting at night that the user did not realize was happening?

 Gotta cover all the bases

Gordy

More Info

Thanks guys for the feedback!  I'm attaching pictures of the heating system I took this weekend.  If they are clear enough the water temp should be visible on the gauge.  I may have inaccurately explained what the contractor was saying.  He indicated that do to the amount of lines in the floor, the most the slab would ever produce is 27,000 BTU's, I believe. 
The thermostat is located on the corner of the entrance hallway.  However, it is outside the closet that houses the heating system.  Another question I have is whether or not area rugs would make a difference on suppressing the heat from the floor?  We have an 8 x 10 wool rug down in the main living area.  I think I mentioned in an earlier post that we have ceramic tile throughout the main floor.  There is also a 3 x 8 rug in the hallway. 
I've probably posted more than enough attachments for this post.  I can post pictures of the interior and exterior of the home if needed. Again, this system is just around 1.5 years old as the home was finished in the fall of 2009.  But I would imagine that failure in the boiler could happen at anytime.  Possibly it could still be under warranty??
Thanks again!

Rugs

 Do reduce output its like throwing a piece of insulation over the floor. Remember the floor is your heat emitter. And wool to boot. About 104 sf of reduced output area. Not a huge deal, maybe 3640 btus. 

 Temp gauge on boiler is saying 120* at that moment could stand to be higher130- 135ish.  It would be nice to know the reading on the temp gauges at the manifold supply, and return also.  flow meters appear to be in the half way range.

  More visual stimulation never hurt anything. share more pics if you wish.


Gordy

Come to think of it, ...

Is the pressure not kind-of high, too? Looks like maybe 30 psi. Hard to be sure, blurry and all. This would have nothing to do with the problems, but should be looked into.

Some more info

Here are a few pictures of the property - inside and out as well as a spreadsheet showing electric usage from 12/19/10 - 2/1/11 for whatever its worth.  If I understand, it would be a good idea to possibly roll up the rugs and store for the winter to keep from blocking the heat?  Would it be worthwhile to go with a slab stat in place of an air temp stat?  I suppose there is some risk in hitting a line trying to drill for the sensor at this stage of the game??  I hope the pictures of system and property will assist in helping solve the problem.
Thanks!

Very nice

    I would do a floor sensing thermostat. 
   Your loop lengths should be fine 3 loops at 1' centers is 240' each loop, or could even be 9" centers at 312' each if 1/2' dia. tubing should be just fine either way may even be 5/8" better yet. This all has to do with the pumping head generated by the friction of the water flowing through the tubing. The longer the tubing loops the more head loss, and the smaller the dia the more head loss. glycol in the system also contributes to head loss
    If you want to find the center spacing. Buy a cheap infrared thermometer 50 bucks. Run it across the floor to find the hottest spot then move until the next peak hot spot. You may have to spend some time in an area to get the jest of which way the tubing is laid. The thermometer will also assist in putting in a sensor, and checking floor temps all around the floor.

    Heavier grade window treatments do wonders in reducing heat loads. Closing window treatments during night time hours can reduce heat loss dramatically. A long with controlling summer time heat gains.

    One other question I would like to ask is what thickness was the concrete floor poured?  The thicker the more mass to warm up even though it is insulated.

    I do not think you have real serious issues. Just think things need dialed in, and make sure the boiler is functioning properly.

 So step one is make sure Boiler is functioning properly as Mark stated earlier.
 Step two make sure the loops are purged of any air.



    Check floor temps with an infra red thermometer to see what they actually are. Check all around the main floor for even temps. a cold section could indicate a loop that is not getting enough flow, or air bound. Once you get a feel for the loop layout you can even find where the loop starts being the warmest, and where it ends being cooler.

    See what supply return temps are at the thermometers mounted on the manifold there should be about a 10-20 degree difference or delta T in the supply, and return temps say 130* supply and 110* return. This needs to be done once the system is steady state. When its coming up to temp out of set back that number (delta T) will be quite a bit larger, and diminish as the system gets closer to steady state when the thermostat is actually satisfied.

  What I would do is observe the system once at steady state say 68* tstat setting. Wait for the next heat call. When it goes check temps at the boiler, then the supply manifold, and then the return manifold. watch them through the whole heat call until the tstat is satisfied. If at the end of the heat call the delta t is 10* to 20* at the supply, and return manifolds. then you have good flow, and you need to bump up the temp of the boiler a little more.  If you have a large delta t more than 20 then you may need to increase flow at the flow meters. It takes time so be patient.

 If you make adjustments let them work for a day or so. There is a lot of mass so changes are not instantaneous. But the slab being insulated does make it more responsive then a slab with no insulation.

Gordy

 

 

Just my opinion

I don't like putting the pump that close to the air scoop. Is this pumping away from the scoop, I can't tell? After the pump looks like it goes right to a 90? Well, anyway this isn't a real huge issue I just don't do it that way. You said there was 3 loops in the slab, is that 1/2"? How long are the loops?

It is supposed to be as close the the scoop/expansion tank as possible.

What is your reasoning for NOT wanting to put it there?

More to the point, the operating temperature of the boiler , if in fact it was operating when the photo was taken, is a little low. I'd crank it up to around 130 degrees F. If it can't achieve those temperatures, then there is definitely an issue with the elements.

ME

Issues

Mark, I have had issues with air if it's that close, just from my experience. After I spoke with the Mfg. they recommended I move the pump father away during installation. Seemed to work have been doing it that way since.

Your milage may vary...

I guess we all have different opinions and field experiences. I have been parking the pumps inlet as close as possible, and have not had any issues that you are having. What happens if there is any considerable distance between the inlet of the pump and the expansion tank is that a pressure DROOP occurs between the expansion tank and the pumps inlet. THis droop in pressure, can in some cases, cause oxygen to JUMP out of the water, thereby compounding any entrained air issues, and or cavitation issues on start up.

With that said, I have seen systems that were TOTALLY screwed up that still produce circulation and heat. Noisy as all get out, but still had circulation and heat. Heat is not necessarily comfort, but is a required component of comfort.

I used to believe that conventional air scoop (and still do) were adequate for good air elimination, but have come to realize that MBR's are significantly more efficient at initial air removal, so this old dog has started using more of the MBR's as opposed to scoops.

I don't subscribe to some of the manufacturers claims that their devices are so good at air removal that they will suck air off the next closest planet with oxygen, nor will they address any trapped air at the top of the system. That comes down to good field practice in getting rid of the free air on initial purge. If you don't do a good job of that, you can expect ongoing problems with air.

As long as we aren't talking feet of pipe between the expansion tank and the inlet you will probably be fine...

ME

I happen to believe...

... that microbubble rmovers are better than plain air scoops, especially for a dumb installation like mine with baseboard upstairs and no air bleed vents up there. But I am not a professionial, so I doubt my opinion has all that much weight.

But one advantage of my Taco 4900 series, and I believe the Spirovent, is that there need be no straight run either before or after the device, and no need for a directional arrow on the device either.

Belief Busters..

JD, I worked with a forensic engineering group out in California during my work as an expert witness on the Entran 2 trials. They tested the MBR against the conventional air scoop and determined that they both took the water to the same o2 content. The MBR did in fact get there quicker, but it didn't remove any more oxygen than the scoop did.

As for straight pipe, I have seen one manufacturer that recommended the straight pipe requirement before and after their device. THeir assumption is that in a district loop heating system, the water will be flowing at maximum velocity ALL of the time. In residential space heating systems with zone valves, that occurs for 2 % of the time.

I have piped directly from a riser, through an elbow and directly into a scoop and not had problems, but have heard of one system that did have issues with that configuration.

Your opinion is always welcome here. You bring a unique perspective to the class :-)

ME

I would not argue with an expert witness.

And since I have a microbubble remover in there, there is no point removing it.

Where it is is straight for a few inches on either side. The manufacturer says to keep the flow through it to less than 5 feet per second. My boiler manufacturer says to use at least one-inch pipe there, and my contractor used 1 1/4 inch, so that should reduce the speed. One zone runs 2.4 gpm (calculated, not measured) and the other runs something else -- I cannot tell what because it is mostly 1/2 inch copper tubing in a slab and I have no idea as to the length, driven by a Taco 007-IFC. The floor area is about 750 square feet and is five parallel circuits of unknown length. I suppose it is more than the other zone since the 5 tubes entering return through a 1-inch one, and the heat load there is about 4 times the other zone.

It is not constant flow. Sometimes both circulators (no zone valves) run, and sometimes just one.

"You bring a unique perspective to the class :-)"

I like that. For me this web site really is a class.

Followup

Mark
Concerning the question in regards to whether or not the system was operating at the time of photo.  Yes, it was approximately 10:45 AM about the same time I took a picture of the thermostat.  You can see the temp on that which had dropped down slightly lower than this temp the night prior. 
Would it be good advice to get a 2nd opinion from another contractor to check out the boiler?  Again, it's not very old...but can't contact the original contractor either to see how it was set up. 
Thanks!

Follow up to your follow up :-)

Here is a link to the O&M manual for your boiler.

http://issuu.com/thermolec/docs/thermolec_electric_boiler_manual

It appears that there are 2 5 KW elements, so it is entirely possible that you have a dead one. However, it also appears that your boiler comes with an outdoor reset, and it may be set to low.

Have the service agent follow the instructions for troubleshooting as spelled out in the manual, and if everything proves functional, then have him increase the minimum or maximum settings to get warmer water out of the appliance.

I would go with 95 degrees F at minimum and 130 degrees F maximum. That should keep you in a comfortable condition. Also, depending upon what the outside air temperature is doing when it is coming out of a deep set back during unoccupied conditions, as it gets warmer outside, it could take even longer to get the place up to temp, but theoretically, it shouldn't because the demand for heat is less.

ME

Pumping away

I install so the pump is approx. 8"-12" away from Spirovent. That is just the issues I have had.

insufficient insulation

I suspect insufficient floor or perimeter insulation.  you have some pretty good low  outdoor temps. 2 inches of foam doesn't do well faced with single digit temps.   correcting perimeter insulation might make a big difference.

try to find out how the place was insulated, get a "sketch" of what they did around the foundation, don't let them just tell you.  

if the tstat isn' t satisfied the system should never shut off.   if you turn the pump off, the boiler will go up to the set point temp and turn off.  that will tell you what the boiler is trying to achieve or if it is achieving its set point.   you have those little temp gauges on supply & return with those little flow meters, so you can figure out(estimate)  btu's into the floor.

check your water temps morning, mid day, and late evening.  maybe there is a night time set back working you are not aware of?

a floor sensor is a waste at this point, wait til you get the room temps where they need to be.

measuring floor temps at various places will give you more info on whats really happening too.

to me, 120F supply water on a slab home seems high if you aren't below zero F.

I like this idea for insulation.  from mich residential code book.

Slab insulation detail

 JP,
  That detail shows nothing under the slab for insulation??

  Not to say its right to do, but I have seen a lot of radiant slabs with NO insulation perform well, and able to heat the structure.  Efficient no, Able to perform yes.

  I think Mark is on the right path.

Gordy

Appreciate all the input

Thanks to all for your comments and suggestions.  Mark, I appreciate the manual on the boiler.  The only info I had from the previous owner was the installation instructions that were left with other info on appliances, etc.  jp, I also appreciate the comments on the slab insulation.  However, I'm not sure how I will ever know exactly what insulation was used.  I'll have to take the builder for his word on what he witnessed that it was insulated.  I guess I can contact the contractor who did the concrete work but the heating contractor is no longer in the area. 
I had a call from the heating contractor we have been working with this afternoon.  He had an estimate for me for installing a TecMark slab stat.  Not sure of the model but his estimate was around $450.  I had just told my wife that I think we should hold off on the stat until we solve the problem of the major heat loss at night.  It was good to see that advice.  I don't believe I want to spend that money and still have the same issues. 
Mark - I do know that this system has an outdoor sensor.  The reason I know is because the contractor unhooked it as it was buried in the snow.  As a homeowner with very little knowledge of radiant heat, I'm at the mercy of the person whose supposed to be the expert on this type of system.  He indicated that it wasn't functioning as it should buried in the snow and with it unhooked it would put out 120 degree water temp as he set it that way??  Again, I've gained much knowledge in my research but still don't understand the system in all aspects.  I'm assuming that the sensor keeps the water temp regulated by how warm or cold it is outdoors.  But I've a feeling from your comments that it may do more than that?? 
Our realtor had recommended him to look at the system and I've heard many positive comments about their work.  Just having doubts that he knows this type of system that well.  It's very difficult to work with this issue when we're 4 -5 hours away.  I guess that goes with the territory of owning a cabin/vacation home.  
From most of the comments made in regards to my issue, I gather that the concenses is this size boiler and loops within the slab should do the job of keeping the heat at the desired temp day and night.  I know there are some things we can do to address some issues, such as add shades to the windows for insulation ( we've discussed that this past week) as well as possibly pull up the rugs during the winter as to not suppress the heat in those areas.  We can also use an infrared heater (Sunheat) for the loft area if need be for comfort. 
Again, I appreciate the comments and please feel free to add more.
Thanks!

Tell me more about your fire place...

It's wood burning, but is it an air tight stove or an open hearth fire place?

Do you commonly fire it up at night?

Does it pull outside air for combustion? Does it have glass doors? Do you run it with the doors open or closed?

Does there seem to be any co relation between the drop in temperature and the use of the fireplace?

Also, are there a lot of can lights in the ceiling?

It would appear, based on photographs and newly acquired information (disconnected OSA sensor) that the boiler is working OK, but you could confirm it a couple of ways. One would be to look at the gage when the house is the coldest. Also, on your supply and return manifolds are thermometers. Tell us what they are doing when it is cold in the home.

Might be worth while to drop a few bucks at home Depot on a non surface contact thermometer so you can see what the floor temperature is, and also look for leaks in the thermal envelope.

Based on what I read in your manual, the OSA reset only does reset and not set back.

Hang in there. We will find your comfort. It might just be an induced infiltration issue.

ME

Might be worth while to drop a few bucks at home Depot on a non surface contact thermometer

How good do these seem to be? Not questioning their temperature accuracy that seems OK, but size of measuring spot, accuracy of the measuring spot vs. where I think it is pointed, etc.

I have a Black & Decker TLD100 and it seems to work OK, but I really do not think I have been able to find where my copper tubes in my concrete slabs are. Some parts of the floor are warmer, some are cooler, etc, but I do not know that I could tell if I had one foot separation or something else, or if they go lengthwise or widthwise in the room.

There may be some technique in using the thing that I am unaware of.

Using an IR gun.

JD, I only use to have the IR non surface contact thermometer. They work great except when reading shiny hot metals, especially copper. If in doubt, cover the pipe with a small piece of masking tape and the emissivity will be corrected.

Before I had my hand held IR imaging camera, I use to place a grid of masking tape on the floor on 2" centers, and would go through and hold the gun directly at the intersection of tape (actually holding it right on it) and mark the temperatures. A digital image if you will. I would then focus in on the highest numbers on a 1" on center basis to fine tune it. It worked, not as well as my imager, but it gave me a mental picture from which to build upon in my minds eye.

As for finding tubes in a floor, you have to have "IDEAL" conditions under which to work. First, you must allow the floor to cool WAY Down, like 5 degrees F lower than the normal MRT. This could take days, depending upon the prevailing conditions. Once cooled down, you then turn the stat up, and allow the floor to start coming out of the deep recovery. I find that it needs about 1 hour per inch of slab thickness. At that point, using my IR imager, the lines are very well defined. Start too early, and they are blurred. Start too late, and the heat has dissipated so much that it just looks like a large mass of glowing heat. It's as much art as it is science. If you have an ODR, it is best to bypass that function and hit the slab with as hot a water as you can get.

In your case, I would check wit the county energy conservation department and see if you can "borrow" their IR imager for a day so you can "see" what is going on.

FWIW, I got an email from FLIR yesterday. THey now have an imager that starts at $1,200.00. I paid $5K for mine less than 2 years ago! I suspect that the Chinese are getting into the IR imager business, and the American companies are trying to corner the market, but that's just my international conspiring minds theory :-)

For purposes of just getting a surface temperature, the Cheapo Depot guns work fine for under a hundred bucks.

HTH

ME

IR cameras, etc.

I looked at the current offerings of FLIR cameras. I am AMAZED at how low the prices have gotten. I have to control my equipment junkie tendencies. I have resisted getting a digital combustion analyzer.  I do have a pH meter and an IR thermometer. But as a retired person on fixed income, I should not be spending these monies.

With my W-M Ultra 3, it is trivial to set the outdoor reset to whatever temperature I want. And since my heat loss when it is 0F outside is well under half the boiler output, I imagine I could put 180F into the slab, though I imagine that would be a really bad idea.

It occurred to me that I might try this in the late spring or summer. By then, I expect the slab would be no hotter than the ambient temperature, say 80F. I could turn off the warm weather shutdown and diddle the reset curve to get 90F or 100F into the slab.  I would want the windows open, though. Living room would be diffciult (carpet with underlay), but the rest is either ceramic tile, marble tile, or asphalt tile right on top of the concrete slab, Since I am not looking for leaks, but just trying to guess spacing and lengths, this should be good enough, I imagine. I assume all th3 spacing is the same, though I could be wrong, of course.

Available radiation

 I'm starting to wonder a little about how many sf of furniture, closets, cabinets, and stairways there are verses the 720 sf of radiated floor area.
 We keep thinking max floor output with every sf available.  Deduct 30sf for an enclosed stairway, 28 sf for a couple of couches,  30 sf for some kitchen base cabinets, 18 sf of fireplace built to theinside, and some closets coupled with the 108 sf of area rugs..... thats 214 sf You get down to 20- 21000 btus of max radiation.  A weekend is just a short period of time really to get a stabilized mrt.  That expansive stone fireplace will really soak up some btus

 Just a thought

Gordy

Maybe, but...

Gordy,

EVERY house with RFH has these issues and items in place and rarely suffer daily drops in temperature. It could have some impact on this home due to its occasional occupancy usage, and need for acceleration but in the case of furniture, couches in particular, they slow the flow, but don't stop it.

I have a high backed couch directly in front of my radiant wall in the mountains, and when I first start it up, the couch is cold, but eventually warms up to around 75 degrees F. It's more a matter of time and MRT coming up and averaging out.

But as we say, your milage may vary ;-)

ME

Mark

 I do understand what you are saying, and that is my thinking also. Every house has this to over come the mass of the interior space. But, (and I got some junk in my trunk) usually from a light setback maybe 5* verses a large setback of 15*. Then to only come out of that 15* set back for the weekend.  We don't know how thick the slab detail is assuming 6" min. And the depth of the tubing when poured which if deep may have some effect.

 I think the boiler is set low as you do. May have been always that way. or it was turned down to that 120 because un occupied who knows.

 I think some data logging with cheap indoor outdoor thermometers are in order as I stated below. As I said it could be losing temps at night during setback also just don't know it.

  If I were the owner I would even let the heat run for the week to see how it acts upon the week end arrival if it is a routine visit.

 This all could be a combination of small variable adding up to the problem, But I'm just an anal student, maybe even an Arnold Horseshack at times set me straight Mark, I love to be taught.

Gordy

frost free protection

Hey gordy,

I think that diagram was for frost free protection of a slab?  but I like that idea for perimeter insulation, going down deep then outward.

even those cheapo IR guns give you details of the area it looks at based on distance from target in the directions book.   I'm pretty sure it just picks out the hottest region.   I like my $30 gun.  and the laser pointer is most likely pretty darn close.  so it should work better for finding hot spots opposed to cold spots.

for starters you can poke around the foundation below the siding.  the chimney side shows part of the foundation below the siding.  if you hit concrete right away, well thats not a good sign.   adding some preimeter insulation wouldn't be that hard.  even if you dug down only a foot and used 3 inch foam.  up here northern mich there was an inspector that FORBID the owners from insulating their perimeter foundation, now they grow flowers year round :)   all thanks to the building inspector.   

Wood Burning Fireplace

I'll try to answer your questions Mark. 
This is not an airtight unit.  It's a Heatalator brand and has an open hearth with glass doors (not very air tight).  I believe it has an air intake vent on the outside.  We've primarily kept glass doors open until the fire is burning quite well.  But I don't believe I've noticed any difference in drop from either operating it or not.  In fact, the end of January, we started the fireplace later in the evening after our kids got back from town.  The temp had dropped by that point.  So I don't think it has a lot of influence on the heat....my guess anyway.
I believe we have some canned lights in the kitchen area....I would need to look to make sure.  The vaulted ceiling in the main area has some recessed lighting. 
When you're talking about the temp readings on the boiler and lines, check those when it drops at night?  I could have my neighbor look at them as it is now.....but the stat is set at 55 degrees.  Although, no one has been there to prove, I believe it is dropping back from 55 degrees when we're not there.  The reason I say this is because my wife found the olive oil coagulated in the kitchen cupboard.  This may be compounded by the fact that I need to address the microwave/hood which is vented to the outside in the screen porch.  The vent is approximately 12" or so long with a hood over top....but no flap to cover when fan not running.  You can feel the cold air under the hood as well as in the microwave.
I'm adding a few more pics of the layout inside the property.
Thanks!

Monitoring temps.

  The easiest way since you are not there all the time is this.

Buy  4 indoor outdoor thermometers they have a 10' probe. 10 to 15 bucks a piece.

Take two of them in the boiler room, and tape one probe to the supply pipe by the manifold, and the other to the return pipe on the return manifold with a piece of pipe insulation covering the probe.
 

  These will tell you the minimum and maximum temps each pipe sees over what ever period you check them just don't forget to reset them for the next go around of monitoring. 

  So in other words in place while you are gone for the week, and return for the weekend you can look at the minimum, and the maximum temps that occured while you were gone during the week while the system was in setback on the supply, and return lines. So the max of each probe would be while the system was running, and the minimum on each probe would be probably when the sytem started a heat call.
 
 The differences between the two mx temps would be the delta T, the same goes for the minimum.


 Take the other two thermometers, and set up a couple of feet in from each outside wall in the center of the house put the probe on the floor with a piece of insulation on it. Now these will tell you the minimum, and the maximum temperature the floor achieve while you are gone during set back.

 Now you have a monitoring system that you can check when you go there on the weekend.

 You can also do the same with these while you are there to see how all the temps react during setpoint.

 You could get anal, and get a fifth thermometer for the center of the room also. That way each loop is monitored.

 Those temps would really help trouble shooting how your system is reacting. Because you don't really know if you are losing setpoint at setback temps during the night while you are not there do you.

  Having these thermometers will also save staring at the temp gauges in the boiler room for hours. You can reset them when you go to bed, and check them in the morning to see the highs, and lows the supply, and return temps, and floor areas achieved over night no watching required.

Gordy

 

Wood Burning Fireplace

Forgot to ask - is there a downdraft or other infiltration issues with the fireplace?

On Hold Up Until Now

Hello.  I decided to get back into my search for a resolution to my heating issue.  I've contacted a couple of contractors, one in particular that has installed the Thermolec boilers, to give some input.  The one mentioned is going to meet with us when we get up to our place again this next time.  The other one is telling me from the details I sent that there aren't enough loops in the floor to give sufficient heat.  He claims that the 3 - 300ft loops will only give 18,000 BTUs at most.  I asked if there could be any difference in lines used as the contractor who looked in January indicated that the system was giving a maximum of 27,000 BTU.  He told me that he guaranteed there was no way to get 9,000 BTUs per loop out of the system.  The max would be 5,000 to 6,000 per loop??
So please tell me how the BTUs are calculated in these systems?  The boiler has the capacity to produce 34,000,  He mentioned that he would probably recommend more radiant panels to feed off the current boiler to help correct the situation.  I just want to be better informed as it appears that I'm being misled by one or both of the contractors that have given their opinion thus far.  Thanks!

Wrong information...

There is a HUMAN physiology limitation to radiant floors. This limit is 30 btus/square foot per hour (corresponding floor temperature of 85 degrees F, ambient tmeperature of 70 degrees F).

It is not a physical limitation. With enough boiler, and the right system/conditions, there really is no known "limit" to a floor heat emitter. With in reason (30 btu/sq foot/hour) a 300' loop, at 12" on center tube placement would deliver roughly 9,000 btuH per loop. Again, this is not a physical limitation, but rather a human physiology limitation. If your feet are in contact with a floor that is greater than 85 degrees F, you WILL break out in a sweat. If you don't, there is something SERIOUSLY wrong with your body...

As we have previously pointed out, you must first make certain that the "system" is working to the fullest extent. If it is, then you need to figure out where the energy is going to.

Start with the heat source first. Are all elements in good shape? Are all contacts connecting the elements in good shape? Are the controls working correctly? Is the pump moving proper amount of fluid? Are all circuits receiving proper flow? Are all connected thermostats properly set as it pertains to their anticipator settings?

If all of this pans out, then you need to start looking for heat leaks in your system.

ME

Thanks

Mark
Thanks for your response to my question.  This is the course of action that I'm going to follow to try to rectify my heating issue.  I appreciate sites as this to help us, who know little about these systems, become more informed.  Also to try to steer a path that will try to resolve the current system issue rather than just add additional supplemental heating to fix the problem. 
Thanks again!
Ray

Rad heat issue

We have run into this quite frequently, and although we dont use electric boilers, a btu is a btu, no matter how it is produced. My experience has taught me that there could be many possibilities for this.
#1 Was the system sized properly. Was there a professional heat loss done for this property. Was there a radiant layout done? It is very possible that your system was never designed properly.
#2 If so, was it installed per specs. I cant tell you how many times I have designed a system that needed supplemental heat, and have recommended panel rads to handle the supplemental load only to hear the contractor or homeowner say, I dont want that. Well, guess what? That job wont heat properly on the cold days if you dont address that issue. Period. If you need 10,000 btu in a given area, and your floor can only give you 7500, you will be having a problem. Slab insulation is another large problem, as you are ideally trying to heat the floor above, not the ground below. Adding or changing things during construction is another big problem. Was the cathedral part of the original plan? You mentioned that you have 1000 sq' with 2 loops. Does that mean that your slab is 1000 sq '? If so, you may have a flow issue, an you are supposed to limit your loop lengths to a max of 300', and at 1 lineal foot per sq foot, that would mean that your loops are too long, resulting in a larger than ideal delta T.
#3 Operation. What is your water temperature? You will need to measure both supply & return temps. Are you using outdoor reset? Do you know what the floor temp is? Are there now rugs where there were none before? We look for an emmisive temp of around 87 degrees, although you can go to about 89 before you start to feel a notacible difference to the touch. 87-89 is where you are neither giving off heat to an object, nor is the object giving off heat to you. If there are rugs, and they werent initially figured into the plan, then you have basically covered up your heat emitters. You will not be able to get enough output. Do you have heat in the loft area? And, another biggie is your fooling with the thermostat. This isnt like the other baseboard hot water, or warm air systems, where you can turn it down when you leave, and turn it back up when you get home. Set it, and forget it is the best thing you can do for radiant. You may think you are saving, but in fact, its costing you much more. It takes a ton of energy to bring a mass like a slab up 10-15 degrees, and will result in a very unhappy homeowner.
Solution. Find yourself a well recommended radiant heat contractor. Do a heat load calculation on your home, taking into account things like insulation, and floor coverings. Include your cathedral areas, and the loft area. When you have the results of that, compare it to the system you have now. Does the BTU loss match the output of the boiler for the coldest day? Does the BTU requirement per sq' equal your floor output ? If the boiler is large enough, and the slab is set up properly, it just could be an issue of adjustment. You may need to increase the water temp. Or, you may need to add supplemental heat. Although I would use hydronic panel radiators, not gas heaters. They are a good fit with radiant jobs, as they have a great radiant value to them. What I would recommend, is using 2 stage thermostats, leaving the slab on stage one, so as long as the slab can heat the space with no problem, so be it. Then, when the temps start to drop and the system cant maintain to +/- 1 degree, the rads would come on, and keep the space at the desired temp, until the radiant can take back over. Not a perfect solution, but one Ive seen many times.
The final thing that I've seen on a lot of cottages, and beach house jobs, is that some were only sized for three season occupancy, and therefore wont heat during winter. No fun for the people that bought it. The panel radiator, 2 stage thermostat solution may be a good fix for that as well, providing you have enough boiler.
Best of luck.

Ah, Thermolec

boilers.

RCO, how old is this boiler? I have about a dozen of them installed, and about ten of them have had similiar problems as yours. Every one of them had undersized electronic relays  for the elements. How do I know? Because every time I have ordered the new contactors to replace burnt out ones, Thermolec has sent out 25 Amp ones instead of the 15 amp originals.

I think I read that the outdoor sensor has been disabled? If not remember that the max temp out from your boiler will be the same for -10*C as   minus 40*C. For some reason they decided that -10 is the lowest that was needed.

Here is the PDF to their manual, it may help:

http://www.thermolec.com/_documentationcache/cd-266-Boiler%20Manual%20Version%2011English%20Canada.pdf

Also check to make sure that an inline timer has not been added to your system, if it has the temp drop could be from that.

But my money is on undersized and burnt out relay or 2.

PS - how much does the temp drop from daytime high to night time low in the winter?

Thermolec

Leo G
This boiler was installed in 2009.  As I mentioned early on, we just purchased in December with the assumption that the boiler was functioning properly.  The temp will consistently drop 6 - 8 degrees at night time.  I'll make sure that the contractor checks the boiler for bad elements or other issues.  Thanks for your input.
RCO

Thermolec

Leo G
This boiler was installed in 2009.  As I mentioned early on, we just purchased in December with the assumption that the boiler was functioning properly.  The temp will consistently drop 6 - 8 degrees at night time.  I'll make sure that the contractor checks the boiler for bad elements or other issues.  Thanks for your input.
RCO

Thermolec

Leo G
This boiler was installed in 2009.  As I mentioned early on, we just purchased in December with the assumption that the boiler was functioning properly.  The temp will consistently drop 6 - 8 degrees at night time.  I'll make sure that the contractor checks the boiler for bad elements or other issues.  Thanks for your input.
RCO

great thread,my stupid?

the temp gauge on the boiler is saying 130 correct.i always assumed you wanted to make 180 degree water from boiler to prevent low water temp returning to boiler.then pipe into a mixing valve and pump out of mix valve to radiant zone.

Its an electric boiler....

No flue gasses to condense, hence no minimum temperature of operation (within reason).

It is 80 to 85% efficient fired (oil or gas or LP) appliances that need to be kept warmer to avoid the production of detrimental condensation.

ME

thanks ME

THANKYOU AGAIN for your info,every day is a school day.

Resolution May Be Found for Our Heating Issue

Hey Guys,
After having a heating tech in to check out the boiler last Friday to find out it was working as it should, we believe we have found our problem.  The tech did a thorough examination of the boiler system and even called the technical person with the manufacturer to double check some things.  All was as it should be.  We again were told that we needed to look into a supplemental heat source.  But the tech spotted a controller on the outside of our house.  I told him that it couldn't be hooked up as we are paying the standard price and was told by the power company that we were not restricted. 
We stopped at one of the electrical contractors in town to check out cove heat panels or baseboard panels.  We explained our situation to the estimator in the office.  He was perplexed as to why the system wouldn't keep the place up to temp.  I told him that early on I had noticed the set up for a 2nd meter so the plan must have been to go with a dual fuel heat at some point in time.  I then mentioned that the heating tech had noticed the control box on the outside of the house which I had not noticed prior.  This fellow said, "I bet you're being restricted on your heating electric and no one is aware of the situation!"(Except for possibly the heating contractor that is now living in Alaska!)   It certainly made sense to me as the off-peak time for the boiler to run would be 11 pm to 7 am.  The slab would finally heat up to start dissipating heat in the later am and then most heat would be gone by late afternoon.  System would be working overtime trying to keep the slab warm. 
Well the power company checked out the controller today and sure enough that is what was happening!  We'll be anxious to see how the system works when fall arrives with colder temps.  Also curious to see how the bills will be.  I would have to believe that the cost would be somewhat less.  Once the slab is warm, the system will be able to keep it as such.  Will find out before too long.
Thanks for all the advice and guidance!  I'll report back once the cold weather arrives.
Ray

WOW

just WOW!

Would never had thought of that one!

Saga Continues

Well, I'm not happy to report back that I believe my heating woes still continue.  I don't think we've seen the drop in temp as we did last winter but it has dropped on some occasions.  We were up last Weds thru Sat and I noticed some fluctuation with the temp thru Saturday AM.  I picked up a digital Honeywell thermostat...just a basic model...that AM and installed.  The temp seemed to stay quite accurate through the night.  I turned it down to 60 when we left Sunday afternoon.  My neighbor checked on it Weds AM and it was spot on at 60.  So maybe the basic thermostat that was hooked up was suspect?? 
Now, on Tuesday PM I checked my billing for the period of 10/24 - 11/26.  We used 1785 KWH for a total billing of $200 for that time frame.  I told me wife we couldn't afford to live there full-time if it was that much for just the short time frame we were there over that period!  We used around 115 KWH in Aug/Sept  and around 325 for Sept/Oct.  Also the fall has been quite mild in comparison to past years.  Of course, since I've only owned it since December last year, I don't have history to go off of for comparison. 
I've a feeling that the system is either not adequate for the structure or we have a heat loss somewhere.  I'm not sure who to contact as the contractor's I've dealt with have just given opinions based on what was happening with the drop in temp rather than doing any actual calculations.  We know the boiler is working as it should but other things are pretty much an unknown to us.  I was hopeful that we would fix our temp drop problem (which may be the case).  But I wasn't counting on the usage to go up like it apparently has.
Ray

Kilowatt rates

What are they after all fees are added in?  I always figure the rate after fees.

If you subtract 250 kw ( summer use)  from the bill. That leaves 1535 kw.

1535kw  x 3412 btus per kw= 5,237,420 btus for the period. Its a guess as to how much heating you did in the period. How much occupied etc. But averaged out over the billing cycle 34 days thats 154042 btus per day or 6418 btus per hour, and 6.42 btus sf.

Dont know the temps outside, or settings inside. What days were heating ETC.
But thats a very ROUGH idea of the btus used for the heat on AVERAGE per day, and hour. If your other electrical appliances had same usage as summer billing.  I think your rates are very high like .11 cents per kw if total bill is correct.  Its hard to say with out degree day data, and actual heating usage.

.11 cents a kw is not the highest in the country, but its not the lowest either. It will put a dent in the bill for sure.
Gordy

Benchmarking

Welcome to the wonderful world of energy usage benchmarking, where you can record, analyse and obsess to your heart's delight.

Gordy has pointed you in the right direction. First, you will need to separate the boiler kwh usage from the hot water, range, lights, etc. Summer bills are a good place to start but many of us get into more intensive monitoring. Second, you will need the Heating Degree Days (HDD) for your location.

One standard benchmark for space heating is btus per year per square ft per HDD. (btu/yr/ft2/hdd).

For moderately cold climates less than 5 btu/yr/ft2/hdd is doing well, but northern Minnesota may be on a different scale. Where under 5 is very good, over 25 is very bad. The benchmark is clearly dependent upon lifestyle, personal comfort zone, and wardrobe as well as the building envelope, solar gain, and the heating system. I don't know if you can get under 5 in Minnesota wearing t shirts and shorts all winter with the house at 75, but maybe someone on this site will come forward with a well insulated, high solar gain, case study.

From Gordy's numbers and some hdd guesstimates I think you may be somewhere between 5 and10 btus/yr/ft2/hdd, but with the hdd data for the last billing period and for an average year, you can get a better estimate.

Found it

http://www.kouba-cavallo.com/bnchmrk.htm

I'm like cattledog a 5 btu a sf house in central illinois will not be a 5 btu sf house in the north.



Gordy

Electric Usage

Ok.  The usage was 1785 KWH @ $.0943 per KWH = $168.33.  The rest was standard service charge of $28 and tax.  We have a 955 sq ft of living space and home is 720 sq ft (30 x 26).  We were there 8 days out of this time frame.  I'll need to check on heating degree days but the zip for the area is 56470.  We had the temp at 55 for most of the time period when we weren';t there. 

living space

Not adding up. 30x 26= 780. If there is a loft area it must be added in to the calculations you are heating it indirectly.

Wrong Dimensions

Sorry Gordy......Should be 30 x 24....square footage is right at 720 for the main floor and 235 for the loft as indicated in previous message.  One thing I neglected to mention is that on 2 occasions for probably a total of 5 days we had the electric heater in the room above the garage on as well.  This heats the room quickly and is kept on low as it would sweat someone out of there!  The room above the garage is roughly 300 sq ft. 

More Information

I haven't quite figured out the process for calculating the heat use.  I've provided info pertaining to the HDD per day for the billing period based on the inside temp for each of those days.  I've also included a breakdown of the monthly bill for the year by billing period showing number of days and KWH used. This is to give an idea of the KWH used during the months when the heat was turned off - May thru Sept.  The square footage of the main area of the cabin is 720 with 235 in the loft.  Floor to ceiling in the main area is 23 foot with 11 foot in the loft area and 9ft in the main area under the loft.

My take on the numbers

6.2 Btus sf.  I was not far off. Average indoor temp for the period was 61 degrees. I used 127 KWH for a summer bill seemed to be more months in that area. Maybe no AC. Were you comfortable at 69* or trying to economize?

I think a lot of the energy is bringing the slab in, and out of setback ,deep set back in your case. Your slab, and interior MRT just does not reach a steady state where the boiler can kind of coast a long, and maintain a temp. thus not using so much electricity.

While 6.2 btus sf Sounds good it is a low indoor setting raise the temp another 8* to 69* heatloss goes up. even 10 Btus sf is not bad.

 I could be wrong, but I personally just think electric boilers, and waterheaters while 100% efficient just do not heat the water quickly like a gas style burner with a good HX design. I liken it to cooking on a gas verses electric stove. The energy is slower to react for electric.

Supplemental Heat Source

So, it may be the best thing to start looking at a supplemental heat source such as a gas heater.  That will allow us a discount on the electric usage on the heating system to around $.05 per KWH.  We have a wood burning fireplace but we like the option to use wood and also know the cost to convert that to a gas insert would be quite high.  The last heating contractor recommended electric panels to use as supplemental heat but that still keeps the rate up there for our usage.  Our issue is finding a good location for the gas heater.  What are the thoughts on vent free gas heaters?  My parents have had one in their home for several years without any issues.
If I'm understanding correctly, we also may be better off leaving the temp set at around 69 evening when we aren't there??  I take it that we are using a good deal of energy bringing the slab from 55 - 60 up to the 69 setting.  It varied this last month as I was experimenting a little with the temp setting when we weren't there.  Up to this time frame, we had always turned the temp back to 55.  The 69 degree setting seems to be comfortable there.  That is where we keep our system at home which is forced air.  However, we do notice it is more chilly near the exterior walls/windows at night with the radiant heat.
I guess in another month or so, I should be able to compare if we are actually gaining anything from last year with the heating system on 24 hours a day rather than the off peak last year.  I would guess if anything we should at least be able to maintain temp. 

Something to think about

Your specific boiler is fully modulaing. At full output it costs 1.10 for every hour it runs. If it were an LP boiler at 2.85 a gallon nothing gained. If it were NG boiler Way cheaper but you do not have NG.

   Once your structure is up to the occupied temp setting your boiler can then modulate its output to the low end cutting operating costs.  Your longest stay is just 4 days at 69* set point. It can take that long just to get everything heated (slab, and all interior mass) to where the boiler can modulate down. Its worth a try before buying gas supplemental heat sources.

New Billing

Just received our December billing for our cabin.  The usage was 1482 KWH for a total of $139.75 ($0943/KWH).  We were only there for 1 day of this billing period.  Again, all other days the thermostat was set a 55.  Of course we've had a very mild December in the upper Midwest so that makes a huge difference. 
Although proibably not a fair comparison, I still have a hard time with the fact that our billing for November, 10/24 - 11/26 - of 1785 KWH @ $168.83. Our electric and NG usage at our home in eastern South Dakota was 1850 KWH @ $142.85 ($.0772/KWH) and $42.99 for NG for a total of $185.84.for a similar time frame for December.  We have a heat pump and NG force-air furnace.  Our home is an 1920-era home with not the best windows and probably inadequate insulation.  It is around 1500 square feet on two floors with another 750 in the finished, heated basement. We have a gas fireplace in the basement plus gas cook stove.  I realize the cost difference in KWH but still it is hard to see why they should be even as close as they are in costs.  I frequently check temps on the internet and they usually aren't that far off from our home to our place in MN. 
I do believe that the new thermostat I installed is doing a better job of controlling the system.  I say this because we spent 3 days there after Christmas and the temp held steady all the time we were there.  I will do a comparison when we get our billing for December here at home which will be at the end of January. 
Thanks!
Ray

setback & control

One day a month?  What about a remotely-accessible stat with deeper setback (like 40 or 45F)?  Do you have thermal drapes or blinds for those windows?  That will help when you're not there.

Raise the space temp 3-4 days before you leave (or if the stat is smart enough, tell it what day and time you want the space ready and it will work out the rest.)

if the stat is smart enough

My thermostats claim to be smart enough to start the heat early so as to hit the desired temperature at the time set. But they are not smart enough. The maximum mine seem to be able to start ahead is 90 minutes. Since one zone is a radiant slab, I need 8 to 24 hours advance to get the right temperature. Similarly, my baseboard has a lot of reset, so it takes up to 4 hours to recover from 4F of reset. The times when that adaptive recovery would really help are the times when it is pretty much useless. I no longer do any reset on the radiant slab zone, and I am still playing around with reset on the baseboard zone. I may cut the reset to 2F up there. I will know better once we get some really cold weather. It might go down to 16F Tuesday night. Design temperature here is 14F.

Nature of the beast

  SWEI I think part of the dilemma is recovery from set back to so the structure is comfortable upon arrival, and during their stay usually short periods.

   Doing a deep set back compounds this IMHO just judging from all the previous trouble shooting posts above.  Yes deep set back will save more energy during vacant periods, but it also will create higher energy use to get the structure up to stable temps for occupancy. This management is compounded when lower more realistic winter temps are realized.

  Couple this with an electric boiler that they have which is just sized to the design load, but undersized for  (pick up factor) in this case recovering the system out of a very deep setback.

  Learning T stats have their limitations as they are designed to sense room air temp, and not the MRT of the space. The MRT is the killer in this equation in that all the mass of the structure has to recover from deep setback.

  I think all that can be done in RSO's case is a lot of experimenting in which the most money can be saved with the least amount of sacrifice to comfort upon their arrival, and stay. Such is the nature of this beast. The only thing
 All I can say maybe  would be the edition of a supplemental pellet stove to cut the chill until the primary system can stabilize if a deep set back method is the road of choice.



Gordy

definitely possible

That deeper setback could make things worse.  Or not.  I'd setup some kind of remote access (or at least try asking a neighbor to go over and turn up the temp several days before I arrived) and see what happens.  Surely Uponor or Tekmar makes something MRT-aware that can be remotely managed?

Covering those windows, perhaps even doubling up or adding a reflective layer might make the difference whatever the control methodology.  Foil bubble may make a terrible general purpose insulation but it can work wonders over window openings, particularly when it's on the correct side (summer or winter) of another insulating layer like cellular shades or thermal curtains.

I agree

With ya on all counts. I beleive the OP was having the neighbor turn the heat on in advance. Question is finding out the correct lead time, and temp.  Window treatments work wonders for insulating. Depending if windows could add solar gain with right orientation on property.............But then all is lost at night. Automatic temp sensitive control comes to mind for that.

Gordy

Suggestions

I appreciate all the comments.  Although the remote programming t-stat would be useful, as Gordy indicates, we do have a neighbor who is generally available to turn the stat up a day prior or day of our arrival.  Again, the time it takes to heat up the place isn't the issue that concerns us.  However, it is the perceived high amount of usage that is required to heat this dwelling when we aren't there much of the time.  Typically, we have used the place 3 to possibly 4 days in a month's time frame.  The November billing was somewhat of an exception as we were there the end of October, the middle of November, and over Thanksgiving for a total of around 10 days.  This current billing for December included from the reading on 11/26 - 12/26 in which we had been there from 11/23 to 11/27.  The heat was turned down to 55 degrees when we left on the 27th and we were not back up until after 12/26. 
I have a hunch that leaving the t-stat set at a higher temp when we aren't there is probably going to cost us more due to the average days of usage during a month.  I have noted that the outer perimeter in the dwelling is cooler as we have an indoor/outdoor thermometer on the north wall.  That registers typically 64 or 65 degrees when the t-stat is set at 69.  However, the comfort level is OK in the place.  Gordy is probably correct in the assumption that the boiler is just big enough to heat the place.  Therefore, it might make the most sense in installing an LP gas supplement heat source to help.  Even if it wasn't used much, it would drop our KWH rate to .0552 from .0943.  The power company stresses that they would be able to control our heating electric up to 400 hours per heating season.  This is typically no more than 6 hours during the day.  As I told them, up to this season, we were being controlled 16 hours a day because we were on an off peak setup unintentionally. 
Our biggest dilemma in a gas supplement is the space for installing such.  We really have no room on the main floor.  We have discussed the possibility of a gas insert for our fireplace but the payback on doing something like that would take years to achieve.  Plus the fact that we enjoy a real fire occasionally. 
Anyway, we know that we have probably solved our issues with the temp drop.  First, by correcting the off-peak issue and then by installing a new t-stat  Unless we are being fooled by the more mild outdoor temps this year! 
Bottom line is that we want to come up with the most efficient and cost effective way to heat the place during the winter season.  I believe possibly the only other option would be electric heat storage units which would qualify us for the off-peak rate of .044 per KWH.  I believe these units are quite spendy as well.  Again, the payback would take several years. 
I'm thinking we should possibly look at a vent free wall heater for great efficiency, initial cost, and rate decrease for the best bang for the buck.  I know that there are a lot of mixed opinions on these units.  In our case, it would be something that would be used occasionaly....when electric is controlled and possibly to help bring out of setback.  We have been looking at blinds as well to help insulate the window openings. 
Thanks! 

No gas fireplace

 The idea that a gas fireplace is going to heat could not be farther from this assumption. When installing a gas fireplace the damper must be open, or removed at all times. Guess what happens then.

Gordy

storage heater

Can you add a water storage tank to your existing system and qualify for the off-peak storage rate?  If so, you should be able to run the existing boiler (possibly adding a second in parallel) on a timer and shift your consumption to match their tariff.

What to do?

Ray,

You are making progress, focusing your concerns and narrowing down your options.

The first thing to try is the deep setback when you are away. I think that the suggestion of setback to 45 is worth a try as long as you can get your neighbor to turn it up. I'd start by adding the same amount of time as it takes to go from 55 to 65. When you work the heat loss math, I think that deep set back and recovery will always take less energy, and with an electric boiler you don't need to worry about efficiency with how hard or easy it is working. But as mentioned there are comfort issues and the difference between the air temperature and the mean radiant temperature (MRT) of the entire mass.

I can see that you are tempted by Minnesota Power's different rate plans. Since your are currently comfortable, but suffering from billing shock, the economic analysis and payback issues are key.

If you go the dual fuel route, there are a couple of considerations. If you go for the propane wall units, I think that you will be much better off spending the extra money for a direct vented, modulating unit. I think that your house is too well sealed for a ventless unit, and the water vapor, oxygen depletion, and CO hazards are substantial. We want you to keep posting.
Best, would be a true propane mod/con boiler tied into your existing radiant system.

I think that the off peak power route also has merit, but you'll have to take a close look at your design day heat loss and the boiler capacity. Since you appear to be sized correctly, you may not have the capacity for significant storage.

The easiest "all you gotta do" is convince MP to give you off peak rates when you are not in residence, and do a large daily swing with heating only from 11pm to 6am with the slab as your storage, and convert to the standard rate for the days you are at the house. This really would be a win/win for you and MP, but unfortunately it relies on the impossibility getting a large utility to do something special.

Fujitsu Mini Split System

What are the opinions of these efficient systems that are available today?  I spoke with a homeowner across the lake from our place that had 2 of these installed last summer in his 2000 sq ft home.  He has been very pleased with the operation of them.  Of course, his purpose was to have a/c during the summer months.  But he has found that they have heated his home quite well this winter.  He said they are very low cost to operate.
My thoughts are that one of these units could possibly help keep the radiant system from working as hard to get warmed to temp.  The bonus would be the a/x availablity in the summer months.  I've had 3 months of heating now and the electic bills have been $172, $142, and $173.  Again, we average about 3 - 4 days per month of use. 
If we were up there more often, I think I would try to leave set at a higher constant temp.  I'm not sure if it would be worthwhile to do so when we are not there on a very regular basis. 
Another question -  does it make sense to turn the water heater off when we aren't there?  I have been doing so each time as that was the practice.  I'm thinking that the water stays fairly warm as there doesn't seem to be much lag time once we are there and turn it back on. 
We've also measured our windows for cellular blinds this past weekend while there.  We've resolved the holding temp issue as it will stay right at the setting we have it on now.  However, I do note that the temp by the outside wall is around 5 -6 degrees lower. 
Anyway, please give opinions.

Thanks!

Looking for AC

 I will comment on turning the water heater down. Beware that legionella will bloom, and the first shower you take after turning it back on will be loaded with that bacteria. see legionella thread on main wall.

Gordy

low temperature performance of mini splits

Ray--

It's encouraging that your neighbor is getting satisfactory performance from his mini split. It's important to understand the low temperature performance of the system, and using them for heating in Minnesota is not the typical application. At low outdoor temperatures, the efficiency and possibly btuh will be lowered, but I think that a mini split will always be more efficient than directly converting electricity to heat. The outlet air temperature achieved at low outdoor temperatures is another issue. You may gain some additional efficiency, but blowing 65F air around the room may not make your feel warm.