Joined on January 19, 2012
Last Post on June 17, 2013
@ June 17, 2013 11:19 PM in Triple Aquatat RElayYou really need to post the model of the boiler and a diagram of how it is wired.
@ June 17, 2013 6:44 PM in Delta t ...... The obsessionJean,
'It sounds like you have your shortcycling under control. I suspect there is a flaw in the way you have measured your delta t on the system side. It would be impossible to get the delta t you describe without short cycling.
Delta t should be carefully considered at the design phase. Not obsessed in the real world.
Glad your system is running so well after the tweaks.
@ June 17, 2013 9:07 AM in Delta t ...... The obsessionI am not really suggesting you heat with light bulbs, just making a point.
As I indicated earlier, I don't obsess about delta t.
Radiant loops have so much resistance that it take an enormous amount of energy to significantly raise the gpm. I do not think there is a circ out there that has a pump curve that would allow a range of say, .5 to 1.5 gpm on a 200' length of 1/2" tubing. I personally do not think that radiant loops are a good application for delta t circulators. They will work quite nicely on a series baseboard application.
I also don't think that the nearly constant circ setup you have is very efficient, it has nothing to do with the speed of your circulator. You have said that your boiler is oversized, I assume you do not have a buffer tank. I appears that you are running your boiler in a short cycle condition most of the day. If you turn the reset curve up a bit, the boiler and circ will run less hours with longer cycles. I would be surprised if this has any effect on comfort. I believe your overall efficiency will be improved. You will have less hours of boiler heat loss, less electricity used by the circulator and boiler, and longer more efficient cycles. Raising the temp will reduce the amount of condensation slightly, in my opinion not enough to be concerned about.
@ June 17, 2013 12:37 AM in Delta t ...... The obsessionGordy,
Thanks for starting this one. I agree with you that it is a design constant. In the real world it will vary all over. A startup on a cold slab will be a higher delta t. Out door reset will lower the delta t. Some of this can be corrected using ecm or other controls. I also think that to some extent, who cares? If a system has a delta t of 15 at cold start up on cold design day, then stabilizes to 10 is it a problem? If the same system drops to 4 when the boiler temp is lowered on a warm day is that bad? I think it is completely normal.
A system with a delta t at zero or one is not giving off any heat unless you are pumping the crap out of it. If you loops are circulating 3 gpm at 1 degree you are giving 1,500 btu/hour to the space, not including the heat lost in the piping and circulator. You could turn on 8-60 watt light bulbs or invite 3 people over and generate the same amount of energy. I think you are wasting energy pushing cold water around the house.
@ June 16, 2013 8:28 AM in in slab radiantJoe,
So sorry your post turned into this ridiculous debate. Please post again if you have more questions.
Jean-David if you have a delta of anywhere near zero, your curve is set too low for your install. If you are just interested in wasting electricity only to gain a little heat, why not just leave a light bulb turned on? You could even put it on a t-stat. The end result will be the same, you just won't wearing out expensive boiler components. Highjacking threads for this kind of nonsense is rude and counterproductive .
@ June 15, 2013 11:10 PM in BACKFLOW PREVENTER vent dripThe backflow preventer is designed to vent when domestic pressure drops below system pressure.
If you install a spring check upstream of the backflow valve, the problem will be solved.
@ June 14, 2013 5:52 PM in High Efficieny Gas Boiler RecommendationYour system clearly works. You are saving energy over a conventional system.
The 10 to 1 turndown on most units costs some efficiency you are less efficient than a 5 to 1 model in most cases.
Navien does not have a particularly good track record over the long hall. They are priced accordingly
@ June 14, 2013 9:11 AM in High Efficieny Gas Boiler RecommendationI don't subscribe to the strategy of oversizing the heat boiler in order to get instantaneous DHW . Just to many compromises. Navian is a completely different boiler, much lower quality and price point.
@ June 14, 2013 8:58 AM in in slab radiantIn real operating conditions, delta t will vary tremendously. Tubing in thick slabs will have higher variations. Low mass applications will be more stable, as Jean-David said they will be tighter as the water temp approaches the indoor air temp.
Delta t circulators help stabilize this somewhat but nothing will completely stabilize it.
I guess I don't see a problem with these fluctuations. If your slab starts getting too wide a range it will create hot and cold spots this can be avoided with proper circ sizing and shorter tubing loops.
Why not design the radiant for a cold day design of 10 degree delta t and figure it will usually be a bit tighter. You have to pick a number as a basis for your design ,10 for floors and 20 for convectors seems to work pretty well.
@ June 14, 2013 8:33 AM in Kitchen heatRadiant floor heat does not have to add weight. Take a look at warm board.
Heating the countertops would be another option. If the tubing cannot be poured into the top, they could be attached the underside with joist track.
Kickspace heaters could be sized to do the job, It just is not as nice.
@ June 14, 2013 12:52 AM in High Efficieny Gas Boiler RecommendationThe first thing to understand is that number of BTU's that your coils are capable of emitting is not the same as the number of BTU's your house will loose on the coldest design day(heatloss calc). Your boiler should be sized for the latter.The home you describe should come in at less than 20btu/ft.
High efficiency boilers perform best with low water temps. The entire system should be designed perform at low temps. It may be that your designer has oversized the coils to achieve this.
Trying to integrate forced air and radiant floor heating is tricky.The whole idea with the radiant is to have warm toes. If you keep the floors warm for your feet, you really don't need the air.
The heat exchanger in the lochinvar is "hands down" superior tovAlpine
Given the scale of your job, and the fact you are still in the design phase, I would get a top quality contractor on board now and rest easy. There are several great long island guys on this site, I would start with Robert O'Brian.
@ June 14, 2013 12:10 AM in summer/winter hookup & oil furnace running when no water is being usedA picture would help. It sounds like you have an indirect coil and your boiler is designed to be always hot.
@ June 13, 2013 11:48 PM in solar heater controlYou are looking for something like this?
You are trying to turn on a circulator when the difference between 2 sensors reaches a certain temperature?
Post a drawing or picture if you need help confirming compatibility.
@ June 13, 2013 8:54 AM in in slab radiantJoe,
1. Shorter is better on the loops. I my mind 200' should be the target 250' the max. Keep the loops within 10% of each other. This will keep your head loss within the range of all the affordable circulators.This also keeps the delta t low and provides a nice evenly heated floor. Everyone will have a favorite, the grundfos 15-58 works well for this application.
2. The mixing is a tricky question. You could use "dumb" mixing valves and just let them "lag" the ODR setting your boiler is firing. It would be better to give them individual "smart" control. You could use either an injection mixing setup or a mixing valve with a controller. They both have pros and cons and I would let the tie in with the existing system dictate. A smart mixing setup would also allow you to prevent cold water from returning to the boiler when the garage zone is running. If this happens it will cause the boiler to condense, this will shorten it's life considerably.
3. Approx 10" spacing would be plenty for a garage.Again shorter loops.
4. Warmboard is a good idea. You will not have much flexibility on tubing layout so it would be good to have good control over the water temp in order to "tweak" the output.
5.You do not need multiple air scoops. Be sure your existing one is in the optimal position in your system. If the expansion is attached to it, the circulators should be "pumping away".
@ June 12, 2013 7:55 AM in Boiler hot, 2 zones, both thermostats turned "Off"This sounds like a controls problem. When the zones are off, the boiler should not be firing and the primary circ should not be spinning. How long is it staying hot? Does the boiler call for heat? I guess I don't understand exactlywhat is going on.
@ June 8, 2013 8:31 AM in retrofit: funky existing radiant floor, some new radiant floor, brand new mechanical room. advice pleaseI am thinking you have far to many closely spaced tees. I would pipe the two boilers together on a common header. They would each have a circ and a check valve.
This primary header would tie into the secondary with closely spaced tees.
I would not use closely spaced tees for the secondary branch zones as it will cause a temp drop from one to the next. A generously sized supply and return header would be much better. You of course will need a circ and check valve on each zone.
In your drawing, I don't think the water will ever get from the boilers to the zones, if you pipe it your way, you will need another circ on the main loop.
I would pipe the dhw as a zone. I would use controls to give dhw priority over space heating.
@ June 2, 2013 10:39 PM in A simple book on hydronic heating?Radiant heating does not need to be as complicated as some people make it (myself included).
Check out this one from Dan. http://www.heatinghelp.com/products/Hot-Water-Heating-Books/26/90/Hydronic-Radiant-Heating-A-Practical-Guide-for-the-Nonengineer-Installer
This site also has great info. http://www.radiantprofessionalsalliance.org/Pages/default.aspx
Mark Eatherton just took it over, look for more good things to come.
Hope you are feeling better soon.
@ May 29, 2013 11:44 PM in Mixing radiators and radiant floor heatThis post on proper piping and flow rate for cast iron rads
A favorite for sure.
@ May 29, 2013 9:37 AM in Mixing radiators and radiant floor heatSomeone needs to do a heat loss calc on your home. This will tell you how much radiation you need in each room. Anyone that does not do this is guessing.
Your existing brick walls may not perform as badly as you think. Because of their mass, they tend to store energy during one part of they day and radiate it later. This works for both heating and cooling.
The existing radiators will likely perform quite nicely at lower temps. In a perfect world the new heaters or floor radiant will be sized to operate at the same low temps.
If you do need mixing, many new boilers are capable of this as well. This allows the boiler to run at as low a temp as possible and maximize efficiency.Aftermarket controllers like tekmar also do an excellent job.
Do not rush this part of the job. The extra time spent calculating now will guarantee a comfortable system with no compromises.
@ May 28, 2013 8:48 AM in Issues with coal fired hydronic heating systemThe reverse indirect is a way to use an indirect tank backwards.The domestic water runs through the coil and the boiler water is in the tank. It is not necessary for your system to work properly as it looks like you already have an indirect.
I would absolutely add a buffer tank and a way to hydrolicly separate the boiler loop from the system side. The attached file might help you visualize.(Thanks RobG). You would have to add the boiler protection piping on the boiler and the mixing assembly on the zones. The indirect would be a heat exchanger coil inside the buffer tank.
I do not know of an inexpensive flow meter. Normally you could just measure the delta T going past a point of known flow. The way your circs are set up that looks difficult. Another way to do it would be to measure the fuel going in,also difficult in your case.
As far as convincing you contractor, don't bother, trying to use math and science with someone that already "knows" the boiler is undersized is not worthwhile.
@ May 24, 2013 8:05 AM in Issues with coal fired hydronic heating systemThe location of the circulators is unimportant. Seigenthaler has written some great stuff on both buffer tanks and indirects. He also talks about the effect of boiler cycling on overall system efficiency. Your coal boiler an additional problem. Once the coal is in the fire you are committed to it even if the load is not there. This is what the buffer does it stores the energy until you can use it. Without the buffer it will overheat the boiler and /or burn inefficiently.