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    TT Smart 80 & Prestige Solo 110 Summer Gas Usage (68 Posts)

  • JustinS JustinS @ 8:13 PM
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    TT Smart 80 & Prestige Solo 110 Summer Gas Usage

    Hi

    I have a Triangle Tube Smart 80 water heater that is connected to a TT Prestige Solo 110 boiler... DWH is set to 140 DEGF with a 6 DEGF differential on the boiler... we also have a recirculating loop... and I believe that there is an anti-scalding mixing valve, as there's a T between the heater output and input that is DHW...

    Right now, none of the DHW pipes are insulated and we're seeing DWH calls to the boiler approximately ever 4 hrs, give or take...

    I don't really know if this frequency is OK but I feel that my natural gas usage may be a little high... this is my 1st summer in my new house so the only point of comparison I have is my old apartment where we used 14 CCF compared to 42 CCF in approximately the same time period...

    Now, my house uses natural gas for cooktop and clothes dryer so I would expect there to be some increase but given that it's just my wife and I, wouldn't you expect less of a difference? Particularly, since my boiler and water heater are supposed to be so efficient?

    Any thoughts? Thanks!
  • Gordy Gordy @ 9:29 PM
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    insulate

    Pipes, and boiler does domestic on high fire so its not going to be 93% efficient at that temperature output. But is way more efficient than a tank style water heater. Maybe widen differential to 10*.
  • JustinS JustinS @ 4:27 PM
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    Recirc System Lowering Tank Temp?

    Something I am wondering... If the tank is storing at at 140 and the mixing valve brings it down to 120 or so, doesn't my recirculating system lower my tank's efficiency by dumping this colder water back into the tank?

    I ask because the SMART is supposed to have only 1 degf/hr loss (though, not clear what ambient temp that's at) and my tank seems to be losing more than that...
  • Charlie from wmass Charlie from wmass @ 4:51 PM
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    you are loosing heat

    through your hot water pipes and recirculating lines. If you insulate them it will reduce the heat loss. Also the use of an aquastat instead of a timer to control the recirculation pump will reduce heat loss as once the return water reaches 100 degrees fahrenheit the pump stops moving the water until it cools again.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • JustinS JustinS @ 4:54 PM
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    Right...

    but aren't I losing more heat by the fact that I am taking 140degf water out of the tank, mixing it down to ~120degf and then re-introducing it to the tank?

    I realize that there is loss due to the un-insulated pipes but what about the above loss?
  • Gordy Gordy @ 6:03 PM
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    Aqua stat

    As Charlie mentioned.

    How big is your recirc pump you only need a little bump.

    Bringing cooler water back to the tank is the nature of recirc. You should not be introducing a lot of lower temp water into the tank. You need to get your lines insulated is most of the problem. And an aqua stat.
  • JustinS JustinS @ 5:03 AM
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    Taco 006-4B w/ Aquastat L6006C

    The recirc pump is a Taco 006-4B - 1/40 HP, I think?

    It's controlled by an aquastat attached to its discharge pipe which is set to 110degf with a 5degf differential...
  • Zman Zman @ 12:01 AM
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    Mixing

    Your mixing valve is not bringing in cold water and reinjecting it in the tank. I couldn't because it would have to somehow displace the hot water. What it does is, circulates the 120 water and then mixes in 140 as needed.
    As mentioned, insulating the line would be the best first step.
    I like a combination of time and aquastat control on recircs.
    Over sized and over used recirc pumps can also cause pipe failure.
    Pictures are always nice.
    Carl
  • Charlie from wmass Charlie from wmass @ 8:35 AM
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    The water moving

    is simply water drawn from the tank pushed back into the tank. Think of the old clothes line set ups with the pulley. No "new water" is introduced. you are simply warming the water that cooled in the hot water distribution piping. The point of the recirculating pump is to prevent dumping the heated water into the drain and replacing it in the tank with cold water until it displaces the cooled water that was in the hot water pipes with hot water to your given faucet of choice. It is better to warm 70 degree water to 140 then 42-50 degree water to 140. This is why the insulation is important as the change in temperature will be slowed, meaning less cycles per day to keep the water warm out to the faucets. You are using a little fuel to save a lot of fuel.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • JustinS JustinS @ 10:28 AM
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    Understood

    but I guess I was getting caught up on the fact that the mixing valve is intentionally cooling the water to 120F and then ultimately putting that back into the tank when the pipe surface drops below 110F...

    Though, I guess since the pump only runs for a short time, I'm not continuously taking 140F and then putting 120F back in...
  • Charlie from wmass Charlie from wmass @ 8:39 AM
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    dryer usage

    I would look at that for savings also. They use a lot of fuel. did your apartment use gas for the dryer and hot water? Did you have to pay for that gas for both units? Does your boiler have a warm weather shut down set to below the current low temps you had for the given month? Was the boiler calibrated with proper testing equipment within the last year?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • JustinS JustinS @ 10:18 AM
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    No

    Only the DHW was gas in the apartment... the dryer was electric...

    I believe that the boiler has a warm weather shutdown but don't think it's configured - thermostats are off so I don't think it matters?

    Boiler was just installed 8 months ago so I believe it was calibrated at that time....
    This post was edited by an admin on June 20, 2014 10:21 AM.
  • Charlie from wmass Charlie from wmass @ 11:03 AM
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    when I was 6

    I believed in the Easter bunny. Many boilers are not calibrated. Check to see if yours was by the installing contractor . Dryers use lots of gas.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • JustinS JustinS @ 1:40 PM
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    :-)

    Good call ;-)
  • JustinS JustinS @ 1:42 PM
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    Calibrating

    What specifically does calibrating a boiler involve?

    Just so I can sound a little more intelligent when talking to installer ;-)
  • JustinS JustinS @ 5:15 PM
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    Do they?

    My dryer says that it has an input rate of 20K/hr - so if we do 5 loads of laundry per week, that's only 4 therms of gas per month, approx, right?
  • RobG RobG @ 12:56 PM
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    I'm not

    I'm not sure you are fully grasping what Charlie and Carl are saying. When you are putting out 120 deg water and bringing back 110 deg, the majority of the 110 deg water bypasses the tank and goes back into the cold side of the mixing valve. As the mixing valve is putting out 120, just a tad of the return water goes into the tank and just a tad of the 140 water leaves the tank into the hot side of the mixing valve to create 120 on the outlet of the mixing valve.

    I don't know if I made any sense whatsoever :-) 

    Rob
  • JustinS JustinS @ 1:37 PM
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    Is That

    Is that because the mixing valve limits how much hot water is removed from the tank - i.e, just enough to bring the 110F up to 120F? And then the same amount of "colder" water is made up into the tank?
  • RobG RobG @ 1:54 PM
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    Exactly

    Exactly, the only time you are putting "cold" water into the tank is when you are using hot water. When circulating it is just displacing enough of the 140 to make the bring the 110 back up to 120.

    It's tough to descibe but I think you've got it.
  • Charlie from wmass Charlie from wmass @ 3:46 PM
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    water does not flow through the cold port

    unless the pressure is lower on the outlet port of the mixing valve compared to the cold water pressure. If you do not open a faucet cold water can not enter the system. the return water comes back, the hot water goes out. Please just insulate your hot water lines.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • RobG RobG @ 2:27 PM
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    Sure it does

    Sure it does, if you have a mixing valve. Have a look at this drawing from a couple of posts back.

    I can't get the picture to copy but look at drawing one from hot Rod on the post "recirculation loop" (It should be two posts down in this forum).

    Rob

  • JustinS JustinS @ 4:13 PM
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    How Does This Look

    Applied the first insulation - how does it look? Tried to make sure that it's properly sealed along the seam... my thinking is that I would just continue the insulation on the other side of the ball valve to the left (towards boiler) and not worry about the bleed valve to the right?

    Also, any recommendations on how to work the insulation around the hardware that attaches the piping to the wall?
  • RobG RobG @ 4:30 PM
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    Lools good

    That looks just fine. Insulate everything you can get to. Even the drain side, hot goes to cold, that is the reason for the insulation. What is it, another six inches? 

    As for the mounting brackets just trim it as best you can. Cut a couple of holes for the wings on the brackets and face the seam toward the wall.
    This post was edited by an admin on June 21, 2014 4:36 PM.
  • JustinS JustinS @ 4:36 PM
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    OK

    OK but how to deal with the mounting hardware? Should I just cut away some of the insulation to allow for it?
  • RobG RobG @ 4:40 PM
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    See

    See my edit above. You won't get it perfect, but just as close to perfect is good enough.
  • JustinS JustinS @ 4:48 PM
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    OK

    Ok, thank you...

    Also, as I did in the picture, I'm intending to wrap the rubber insulation as much around elbows but not sure what to do about Ts

    I guess that I could cut into the insulation around the T along the main pipe and then just lay another length for the T itself... alternatively, I guess I could use foam T segments but those don't seem to come in the rubber foam I got here...
  • JustinS JustinS @ 5:35 AM
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    Suggestions

    In this picture, you can see the recirculation pump and its aquastat...

    How should I insulate the piping that the aquastat is up against since it covers the front of the pipe? I won't be able to seal the rubber so not sure what to do...
  • RobG RobG @ 3:03 PM
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    Insulating

    Just trim the foam around what you have to work with. There is no science to it, just do the best that you can and it will be fine. The aquastat has an enclosed bulb so once again just get it as well insulated as you can. As someone said earlier in the thread " you are using a little energy to save allot of energy". In an ideal world whomever built the home should have had the lines insulated prior to closing in the walls. Post some pictures of the rest of the system and we'll see if there are any other modifications that can be done to improve the system efficiency / operation.

    Rob
  • RobG RobG @ 3:03 PM
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    Insulating

    Just trim the foam around what you have to work with. There is no science to it, just do the best that you can and it will be fine. The aquastat has an enclosed bulb so once again just get it as well insulated as you can. As someone said earlier in the thread " you are using a little energy to save allot of energy". In an ideal world whomever built the home should have had the lines insulated prior to closing in the walls. Post some pictures of the rest of the system and we'll see if there are any other modifications that can be done to improve the system efficiency / operation.

    Rob
  • JustinS JustinS @ 9:57 PM
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    Cooling Period

    My ambient is approx 70F with storage at 140F...

    Prestige Solo 110 heats water to 186F with the tank ultimately getting as high as 148F... The boiler fires when the tank drops to 134F...

    With no use, this happens about every 4 hrs... This translates to 3.5F/hr which seems pretty high... Do you have any thoughts on this? I am in the process of insulating the DHW and boiler piping...

    We do have a recirculating pump that runs when the pipe exterior drops below 110F and stops when it reaches 115F... There's also a mixing valve that is set to about 120F or so on the tank outlet pipe...

    Any thoughts on why the tank is losing so much heat so quickly? It's supposed to be rated at 1F/hr at 120F storage vs 70F ambient...
  • JustinS JustinS @ 5:31 AM
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    Recirc Pump's Mostly Off Now

    and I'm in awe...

    I got up this morning to check on it since I turned down the Aquastat as far down as it could go (past 65F on the dial)... whereas before, the heating cycle appeared to be about every 4 hrs or so (with no use), the last cycle was almost 8 hrs ago and the temperature in the tank is still 144F...

    So by seemingly disabling the pump, I've gone from what appeared to be ~3.5F/hr loss to ~0.5F/hr... this new loss seems a bit low, considering the tank is rated at 1F/hr w/ 50degF differential but I guess it is what it is...

    It would seem that the pump is responsible for a significant amount of heat loss to the tank...

    Any thoughts?
  • JustinS JustinS @ 6:28 AM
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    Must Have

    Missed a cycle or something yesterday morning because it looks like the cycle is now about every 8 hrs - not sure why it was 144F yesterday AM after running 8 hrs prior... seems odd
  • JustinS JustinS @ 5:17 PM
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    Here's the system

    As requested, here's a picture of my system... as you can see, I'm in the middle of insulating - I've pretty much finished the DHW piping around the boiler, still need to do in the ceilings between the I-trusses... worth doing, right?

    Thoughts?

    Also, on the Aquastat L6006C - I would like to stop it from closing its contact that starts the pump - I see that its setpoint range is 65F to 200F but the dial goes below 65F - can I set it even lower and prevent it from working?

    I'm just wondering why I am still losing so much heat from the tank so quickly (3.5F/hr, as noted above)

    P.S.

    Why is the pic upside down? it's not like that on my computer?
    This post was edited by an admin on June 27, 2014 5:23 PM.
  • Zman Zman @ 10:15 AM
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    Copper

    Bare copper is a great conductor. It is just giving up heat to the surrounding air.
    Insulate,insulate then insulate some more....
    A circ with a combo temp-time control will also help.
    Your tank losses are about right
    Carl
  • JustinS JustinS @ 10:36 AM
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    About Right?

    Which losses are about right?

    I've already put as good rubber insulation as I could find on all of the DHW copper piping - it's about R 3.3 - how can I put more? Working on the PVC now but that doesn't seem as bad as the copper in terms of heat loss...
  • Zman Zman @ 8:49 AM
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    About right

    The 0.5 is what I would expect from the water heater with no recirc.
    3.5 is not out of the ordinary for an insulated recirc line.It works out to about 1,000 BTU/Hr. With natural gas, that is about 1 cent per hour.

    If you post the size and length of  the pipe as well as the average temp around the pipe it can be double checked..

    There a good chance that the dial on your indirect tank has been bipassed. The better way to setup that system is to pipass the tank dial and install a  sensor that is read by the boiler. If the boiler shows the DHW temp in the info menu, the dial has been bipassed.

    If this was my system, I would set the tank temp on the boiler to 120 then activate the anti legionella feature in the setup menu. this would reduce you tank losses slightly and allow the boiler to condense through more of the DHW cycle.

    Carl
  • JustinS JustinS @ 9:22 AM
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    Don't Understand

    The heat capacity of water is ~8.3 BTU/gal-F, right?

    Since my tank is 70 gallon capacity, wouldn't the loss work out to be ~2000 BTU/hr (8.3 x 70 x 3.5)?

    Also, not sure why I observed a loss of ~0.5F/hr yesterday morning but now it's more like 1.8/hr as the temp is going from 150 to 134 in about 9 hrs or so... not sure why that changed...

    As to the length of pipe - I'm not sure how I would be able to determine this since much of the pipe is unaccessible in the walls?

    Yes, there is a thermal sensor in the tank that is connected to the boiler...

    As to adjusting the tank temperature - what would you use for the temperature of the boiler water? Right now, it's set 46F above storage temperature...
  • Zman Zman @ 5:24 PM
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    you are correct

    I thought you had a 40 gal tank.

    Most recirc lines return water from the farthest point of use. If you estimate the supply and return to that point that is the number you need. How much is and is not insulated?

    The TT boiler has tons of hot water adjustments.

    If you want long boiler cycles, just change to on/off differentials.

    For longer time in the more efficient condensing temps you can lower the tank temp and the 46 degree "add" temp you are referring to.

    Because you live in the house, you can make adjustments until the output is unsatisfactory then dial in the sweet spot.

    Keep in mind most electric water heaters only use about 16k/btu. You have a lot of room to tweak the settings.
  • JustinS JustinS @ 5:56 PM
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    Condensing

    Don't I have to have the return below 130F in order to operate I condensing mode?

    What efficiency am I operating at now? 87%? Or would it be lower since I am heating to 186F?

    Is the efficiency separate from the amount of gas being burned? I think so but want to be sure... I know that on e supply temp is up to set point, the boiler firing rate is drastically reduced... I've seen it as low as 18% - is that 18% of my 30k to 110k BTU?

    Would I really use less gas running longer? Would the. Oiler be that much more efficient at lower temp?

    What do you mean by 16k/but for electric heater?
  • SWEI SWEI @ 6:28 PM
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    Condensing mode

    is actually a misnomer.  As the boiler water return temp drops, efficiency goes up.  As efficiency goes up, condensation increases.  Cold DHW lowers boiler return water temps significantly.
  • JustinS JustinS @ 8:38 PM
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    Dew Point

    I thought that the water vapor in the flue gas couldn't condense unless the return water temperature was less than its dewpoint - which I thought was ~130F...

    And isn't the other way around? Efficiency goes up because of the condensation?
  • SWEI SWEI @ 10:45 AM
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    Cause and effect

    are inexorably intertwined here, and not really the point.

    Let's assume for your particular location, weather, and fuel that condensation begins at one very specific temperature -- say 130ºF.  The efficiency difference between return temps of 129ºF (we'll call that condensing mode) and 131ºF (we'll call that non-condensing mode) would be almost immeasurable.  The curve is smooth and has a low slope.
    This post was edited by an admin on June 30, 2014 10:47 AM.
  • JustinS JustinS @ 10:54 AM
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    Right

    I realize that the efficiency doesn't just jump to 95% or whatever at a sliver of a degree below the dew point... just clarifying that you can't condense at 150F or whatever above the dew point...
  • JustinS JustinS @ 7:44 PM
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    Length of Piping

    It's hard to say for sure since I don't know the path of the recirculating loop but it's probably about 70 ft of piping that's in the walls that I won't have access to in order to insulate...

    There's maybe the same amount in the basement that I will be able to insulate...
  • Zman Zman @ 1:29 AM
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    Condensing

    Attached is a presentation that should clear up the condensing question.

    My point about the electric water heater is that if you multiply the wattage of the heater coil by 3.412 you will get the Btu output. Most heaters are around 5kw. I say this because people who install regular electric water heaters on there jobs love to make a big deal about oversizing  boilers for the DHW load when they do indirect jobs. It just does not make sense.

    Back to your setup. You have a boiler with 110K/btu input. derated  for efficiency it will put out between 90 and 100 k/btu. At 18% firing, it will be putting out 18% of that number.

    By the nature of  heat exchanges the return temp can never be lower that the tank temp. By turning down some settings, you should be able to keep the return boiler temps under 130.


    Your indirect has a great deal of surface area relative to the boiler size. This means you do not need a 46 degree add. I would set the the add to about 20 degrees and the tank temp to 120. I would leave the on/off differentials alone. The anti-legenella should be turned on and the DHW timeout I usually set to 90 minutes. If you have a variable speed circulator on the DHW turn it to low.

    Keep in mind all this is chasing approx 5% in efficiency.

    By turning down these settings you may run the risk of the DHW cycle taking too long and short changing the heat load. Keep an eye on this.

    Carl
  • JustinS JustinS @ 6:28 AM
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    Thanks!

    That presentation looks quite informative - I'm sure it'll help a lot!

    Regarding setting the tank temperature to 120F, wouldn't this mean that I wouldn't have maximum hot water for a portion of the cycle (how ever long it takes to fall from 120 to 114 relative to the final temperature after heating is done)?

    My dishwasher says that a minimum of 120F should be available to it...

    As for the DHW Timeout - are you referring to the period of time that the DHW circulator pump continues to run to remove heat from the boiler? I think that's my DHW Post Pump Time... right now, it's only set to 1min...
  • Zman Zman @ 7:18 AM
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    Settings

    If you need higher than 120 then so be it. I would play with the lower numbers and see how you like it. 120 is not a magic number for dishwasher sanitation.

    The DHW timeout setting is not the same as post purge. It is designed to prevent the house from getting cold in the event of a very long DHW cycle. It will make the boiler switch back to heating mode after a set amount of time.
  • JustinS JustinS @ 7:46 AM
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    Gotcha

    I see that setting now - DHW Priority Timeout...

    Would you increase the DHW Post Pump Time - seems like it would be a good idea as the boiler stays quite warm for several hours after a DHW call - might as well get that heat out of there as much as possible...
  • JustinS JustinS @ 9:10 PM
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    Recirc Pump Cycle Time

    I re-enabled the pump this afternoon and was rather surprised at first to discover that it seemed to be running about every 5 minutes or so for about 90 seconds... over time, I noticed that the time between cycles was increasing from 5 min to 8 min to 9 min - the last time I measured it, it was 18 minutes between cycles...

    What could cause it to vary so much? Not sure about the lower variations but the 18-min cycle was right after the boiler finished heating so I guess heat was diffusing up through the cold water inlet of the tank? Maybe?
  • Zman Zman @ 10:57 PM
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    Cycles

    I have never messed with the post purge setting. I would concerned that it would create a delay between the DHW and heat cycles.The logic in the controller may overide.

    You could observe how long it takes to equalize the DHW storage with the Boiler temp and set it for that amount of time.

    I think your thinking about the recirc aquastat being effected  buy the tank is correct.

    Carl
  • JustinS JustinS @ 5:44 AM
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    Another Thing

    Another thing that I noticed - I was fiddling with the temperature-sensing wire yesterday, I think I pushed it in order... later on, I noticed that the DHW cycle was occurring more frequently - maybe every 2 hrs or so? The historical curve was drastically different than before...

    So I was wondering - what did I do?!?

    I then remembered that I had touched the sensing wire and pulled it out some...

    This morning, I noticed that the boiler only cycled once during the night and the curve looked much like before...

    I tried looking in the SMART installation docs as to how far down the wire should be but didn't see anything obvious... putting it down until I can hear the sensor against the far end of the thermowell seems to shorten the cycle a lower - now, I know further down is cooler (especially with the recirc pump running) but really? That much of a difference?
  • SWEI SWEI @ 9:43 AM
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    Sensor locations

    are significant, as you have just witnessed firsthand.  Now that it's picking up an earlier signal, you might try increasing the differential a bit.
  • hot rod hot rod @ 1:18 PM
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    always use heat transfer paste

    many times the sensors are not controlling accurately due to bad thermal conduction.
  • JustinS JustinS @ 6:43 AM
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    Location

    So should it making contact with the bottom of the thermal well?

    Seems like would be the most accurate reading of the water temperature since it's in direct contact with it...

    Where should the heat transfer paste be placed? Down into the thermowell?
    This post was edited by an admin on July 2, 2014 6:51 AM.
  • JustinS JustinS @ 6:51 AM
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    Recirc Piping Temperature

    The other day I attached a digital thermometer lead to the copper piping around my recirculating pump... I noticed that the rate of change seems to vary a good deal but often the temperature falls by appreciable amounts (as much as 0.5F) over a 5 second interval.

    It seems like the answer would be yes but I am wondering - is the water in that pipe really cooling that quickly? I still need to insulate that pipe but wow, that seems really fast...
  • JustinS JustinS @ 5:08 PM
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    Lowered Storage Temp

    OK, so I've lowered the storage tank setpoint to 126F with a differential of 6F...

    While the return temp wasn't less than 130F once the boiler got going (more like 140F), its firing rate was rather low - it even spent a good part of the cycle at 0%...

    What exactly does 0% firing rate mean? Does that mean it's truly not firing OR is at the bottom of its modulating range (i.e, 30K BTU/hr)?
  • Zman Zman @ 7:56 PM
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    0%

    I believe that 0% is off. You could confirm by looking in the glass window on top of the exchanger.
    What is the supply and return temp when it is at 0%. It sounds like the flow rate is not right
  • JustinS JustinS @ 8:45 PM
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    Temps

    Supply was right around set point of 146F and return was maybe 6-10F below?

    What is the glass window? Look at what in it?

    Why do you say flow rate is not right? What flow rate?
  • Zman Zman @ 10:28 PM
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    Window

    Inside the cabinet, on top of the heat exchanger is a window where you can view the flame.
    The boiler will sometimes get confused if the delta t is too tight between supply and return. Yours sounds pretty normal. Do you have a multi speed circ?
  • JustinS JustinS @ 5:20 AM
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    Gotcha

    I'll take a look at that next time it's in a cycle...

    Yes, the DHW circulation pump controlled by the boiler is a 3-speed Taco pump - it's currently set to Medium - I remember you suggested setting it to Low, haven't had a chance to do that yet...
  • JustinS JustinS @ 6:43 PM
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    No Window?

    Tried looking for a window while the boiler was on but I didn't anything like that, nor did I see any flame...
  • SWEI SWEI @ 7:27 PM
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    Window is on the top of the heat exchanger

    You need to remove top jacket access panel (the rear half of the top cover) or find a moderately long dental mirror in order to see it.
  • JustinS JustinS @ 11:28 AM
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    Turning Off Recirculating Pump => Significant Impact

    So I turned the recirculating pump off about 4 weeks ago and the result is quite significant...

    The boiler went from running every 4 hrs or so to only 2-3 times per day... There is generally 12-14 hrs between firings now...

    Part of my problem, I think, is that the piping isn't insulated in the walls...but I am also wondering if perhaps the fact that the DHW return piping merges with the cold water inlet to the tank before the scalding valve...

    Earlier people had said that the scalding valve should only let minimal amounts of hot water from the tank out, enough to bring the DHW return back up to 120F... Seems to me that this would be the case initially but once hot water leaves the tank, it needs to be replaced and this would be with a mixture of DHW recirc and cold water from the street...

    What do you think?
  • Zman Zman @ 12:48 PM
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    Cold water

    You are correct that the heat you are loosing is through the uninsulated pipes in the house.

    As far as your concern about cold water entering the system. Water is essentially incompressible right? You can only fit a finite volume of water any piping system. Unless someone opens a water valve somewhere in the house, it would defy the laws of physics for the cold water to enter the system. It would have to displace the the water that is already there and it cannot.

    There are formulas that will estimate the heat loss through insulated and uninsulated pipe. What you are witnessing is consistent with uninsulated pipe.

    An difficult but important concept to get your head around.

    Carl
  • JustinS JustinS @ 1:06 PM
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    Yeah

    That makes sense... Thanks for the explanation... I guess I was getting confused by the fact that the recirc water is going both through the scalding valve and into the tank...

    Disappointing that the copper piping around the pump still loses so much heat even after I insulated it...

    I guess that the recirc pump is putting a lot of cooled water back into the tank... Too. Bad
  • SWEI SWEI @ 1:11 PM
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    That 5ºF differential

    on the aquastat is a big part of your issue.  You might look at a demand-based trigger to start, then allowing the aquastat to turn the pump off once the water arrives.
  • JustinS JustinS @ 1:33 PM
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    Demand?

    What would the demand be based on?
  • SWEI SWEI @ 1:43 PM
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    Demand start of pump

    Can be triggered by a button press (on the way into the bathroom or kitchen) or using an occupancy sensor (easiest way is to power the pump from one of the light circuits and use the occ sensor to do both jobs at once, but there are other options as well.)  This way the pump only runs when you need it and shuts off once the aquastat trips.
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