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In Floor Heat

Got a question about supply and return temps for my infloor heating. I have a Bock 32 BCS E with a EZ-Gas burner (natural gas). In floor is heated by a loop to a heat exchanger then I have three zone valves controlling heat oneach of my floors. Total squre footage is 1500. I live in Alaska and now the WH is set at 140 with domestic cooled down to 120. What should I set my supply temp at and what drop should i see in the return side. I have Rehau manifolds with adjustable loops on GPM. Now I am set at 115  with return of about 100. Is this right or should I be lower on supply temp. 2nd floor has tubes underneath flooring with insulation below pipes that are stapled up to bottom of floor with heat plates.3rd floor is in lite weight concrete and 1st floor is in concrete. Need some help setting this up, Thanks for any advice.

Comments

  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    It is really tough to answer a question like that.

    I live in New Jersey and where I am, the design day temperature is 14F. I keep an inside temperature of 69F. To provide a little margin of safety, I assumed an indoor temperature of 70F. My house is about 1150 square feet, so I calculated about 35,000 BTU/hour heat loss. My radiant heat is copper tubing in a concrete slab, but I do not know the spacing of the tubes, and I do not know if there is any insulation under or around the slab. The water table is six feet down. I have outdoor reset and run the supply to the slab from 75F until it gets down to 54F and it then slopes up to 120F at 2F outside. This provides enough heat, at least down to 9F by actual test last winter. It has gone down to only 17.4F so far this winter. Return temperatures are not much less than the supply temperatures when it is warm out, and are only a few degrees less than the supply when it is very cold out. I suppose I could put a delta-T ECM circulator in there and get greater temperature drop through that zone, but that would probably make the heat distribution less even, and would be an additional expense, so I have not done that.



    Now everything is different for you. Depending where you are, design day is 1F in Juneau, -18F in Anchorage, -27F in Nome, and -47F in Fairbanks. So depending where you are, different temperatures will be required. Similarly, depending on the heat loss of your house. Also, it is my understanding, as a non-professional, that higher temperatures are required with staple-up tubing, and even higher if you do not use aluminum heat-spreading plates. Also, I wonder, in a place like Alaska, whether a hot water heater has the capacity to keep up with the heat loss you might expect.
  • icesailor
    icesailor Member Posts: 7,265
    Bock 32E BSC

    I don't think you are supposed to use that water heater in the application you are using it for. The tank will fail quickly and there will be no warranty. If has no UL listing for that and Bock doesn't list or recommend that install. The cold water circulating causes massive condensation causing tank corrosion for the same reason that letting a PRV on a boiler leak and fresh water is continuously add to a heating boiler will cause it to fail prematurely. Ten or more years ago, a bunch of installers thought they could get a quick, cheap job using water heaters as combo units and had all failures. Bock oil units were very popular because they are just a steel boiler. They start to rust and then leak. If yo personally made that choice, it's your choice. If someone made it for you, I suggest you contact Bock and ask them about it.

    Seen that, never done that. But seen and heard about a lot of failures.

    And in Massachusetts, there is something about not directly using the heat generating source of the building with the domestic water heating source of the building. Because of scalding. Read the warnings on the Bock web site.
  • hollywd
    hollywd Member Posts: 9
    bock 32bsc e

    I live in Big Lake , Alaska.This has been in the house for over 10 yrs. A plumber installed it . I have a space issue ,this was previously a oil burner that got converted over to natural gas when it finally rolled into the neighborhood 6 years ago.I have a mixing valve( anti scald) at heater for domestic hot water.The in-floor heat is on a closed loop that goes thru a heat exchanger off a loop that is fed by WH.Bock put extra nipples on side of  WH just for this purpose or so I was told by plumber and Bock years ago. House is super insulated and Pipe was put in by design spec for my house. Heater keeps up with demand even well below zero, as it often does. Has a little trouble at -50 but what heater wouldn't.

    JDB does your pump run all the time ,also I do have staple up aluminum plates with insulation underneath. Works a little harder to keep up on that floor, others with concrete are awesome!
  • Gordy
    Gordy Member Posts: 9,546
    Not enough information, and it Depends

      On your room by room heatloss calculation of the structure.  This will dictate your supply temps, and flow rates.



      You also have three different radiant heat installations. Ist and 3rd floor could run similar temps but second floor will need higher temps.



     Is the dwelling 1500 sf, or the amount of installed radiant 1500 sf?  Is there 500 sf each floor?



     Is the mainfloor slab insulated?



     Obviously its not an open system since you have a HX on the water heater.



    You have three zones I one for each floor. Either you have wide tube spacing, or very long loops niether one being a good idea for design. Depends on how the floor sf for each story is.



     As far as tank style water heaters go they all condense more with a radiant install than just being used for domestic supply. Being your using a HX this takes alot of the condensing issues out of the equation.



     People get to wrapped up in delta t.  This is used for design criteria. When the system is running the emitter end delta t will vary from initial start up heat call until load is satisfied closing the delta t gap until the call is satisfied. Unless using constant circulation then delta t will be a more stable number.



    Gordy
  • Gordy
    Gordy Member Posts: 9,546
    So whats your issues

    Missed your post response while typing mine.  Is the staple up the issue?  Not understanding you need help setting up if this system has been in place working fine for a while.



    Gordy
  • Gordy
    Gordy Member Posts: 9,546
    Supply temps

      Basically you don't want to be over 85* floor SURFACE temps max for comfort.



    The staple up will by the nature of design take higher supply temps to satisfy that zone. The lower the supply temps the longer the call will be.  What kind of floor covering is on the staple up zone?  This will reduce output if a high r value floor covering.
  • hollywd
    hollywd Member Posts: 9
    in-floor heat

    Hey Gordy,thanks for the posts.



    500 sq  per floor ,maifold for each floor with 3 loops on each floor

    1st floor (daylight basement) insulated underneath pipes under slab (Tile and some carpet)

    2nd floor staple up with aluminum plates (tile and laminate)

    3rd floor -all tile- gypcrete

     Just wondering never got a good answer from installer, have always shot for 115* out and 100* on return side. Just thinking because a loop on second floor is froze up when heater didn't restart while away for a couple of days. Waiting for it to thaw out.

    I will check on temps to make sure i am under 85*. Had some time on my hands and wondering how to improve heating on second floor. Speed it up or slow it down, I can do that on manifolds and balance each loop out.Thanks for all your help everybody!
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    pump run all the time?

    No. I would like it to run about 3/4 of the time, but controlled by the thermostat. I.e., I would like the system to heat just enough to make up for the heat loss. The reason for the 3/4 is so if it got too cold, it could make up for it by running longer. Because if it didn't, I would have to go out to the garage and diddle the reset curve for the zone in question; I really do not wish to diddle the reset curves. Good thing I know how to do it, because if I had my contractor do it, it would involve many many service calls over the last year. It takes a long time because I have no control over the actual outdoor temperatures.



    When it is warm out, the circulators run a much shorter time, because if I lower the supply temperature to a zone too much, the boiler cannot modulate low enough, and it short cycles. This is not really a problem for my downstairs (radiant in slab) zone, but it is serious for my upstairs (baseboard) zone. There are techniques to reduce short cycling, and in my upstairs zone, I do them all:



    1.) Run the baseboard hotter than I would  like so generated heat by the boiler is rejected into the rooms faster than absolutely required. This makes the time necessary to run shorter, and the run time longer (but not enough longer). I use 110F as the minimum to the baseboard. It works fine from a heating point of view at about 80F, but the boiler short cycles because there is almost no temperature drop through the 28 feet of Slant/Fin with such cool water in it, so the boiler rapidly climbs to the high limit.



    2.) Increase the hysteresis from the default (+|- 5F) to (+7 | -8F) to let the boiler run longer before it shuts off, and idle longer before it restarts.



    3.) Lower the maximum firing rate from the default (94%) to 55%, so the temperature climbs more slowly, allowing the reset control time to lower the firing rate before firing is stopped by going too high. The reset control seems to be Proportional Integral Differential and it works too fast considering the lags in the system.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    heater didn't restart

    Why did not the heater restart? Too much setback on the thermostat while you were away? Fault in the burner? Gas pressure regulator defective? Tired ignitor? Tired HV transformer if spark type ignition?



    My boiler has a freeze protection component to its control. Provided there is gas and electricity, it fires up the boiler to low heat if the boiler temperature drops to 40F, no matter what the thermostats are saying. It can turn on whatever circulators I ask for. I have the boiler circulator and the circulator to the slab both run. It shuts off again when the temperature of the boiler gets up to 45F. I have never tested this as my thermostats all turn on when the house temperature drops below 69F.
  • Gordy
    Gordy Member Posts: 9,546
    Sounds Like

     You have a good design. Was worried there was 1 loop for each floor, but you are saying three loops each floor, and each floor is its own zone correct. I'm Thinking original installer thought maybe the staple up would take lower temps due to floors above, and below contributing some heat to second floor.



     Raising your flow on the second floor manifold may help a little. Is each zone controlled by its own circulator? Or is there one circulator for the whole system with zone valves for each floor/zone?



    Constant circution may have been a benifit to deter freezing IF you did a deep set back while away, even if water heater shut down....unless you have a power outage. It also helps lower delta t which evens out floor temps.
  • hollywd
    hollywd Member Posts: 9
    in-floor heat

    I only have one pump and 3 zone valves. Never set back thermostat, always leave at  69*. Had a couple of big wind storms in which power fluctuated a lot and that is when heater didn't restart. I thought maybe I could install something like a UPS to smooth out  power surges , if that was problem. Also thought slowing down flow on loops would be better to let heat escape from tubes, am I thinking wrong. Other floors great! How would I get pump to circulate and not call for heat.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Mish Mash of Comfort and radiant tube applications....

    You should actually have 3 different water supply temperatures. Highest would be for the staple up, medium for the gypcrete and lowest for the concrete pour. Without it, you will only be comfortable in any one given zone. You will be too hot in the basement, somewhat OK in the gyp zone, and cold in the staple up zone. As Gordy pointed out, it is really dependent upon R value of floor finishes, and how big the load per square foot is.



    With your house being finished, it is going to be (possibly) tough to reconfigure teh system to meet all the different temperature needs, and it sounds as if the installer was trying to hit the "average" temperature necessary to satisfy the calls.



    The concrete typically needs fluid temps around 105 degrees F, the gyp may need temps as high as 140 F, and the staple up may need temperatures as high as 170 degrees F. The average of the highest and lowest under that scenario would be 138 degrees F.



    Differential will vary depending upon which loads are on line, and the actual load being imparted, but are rarely seen at the "ideal" of 20 degrees F. THe higher the flow, the better. Don't worry about the btu's getting off of the train. They know how to do that regardless of how fast the train is moving.



    The best you can do would be to raise the operating temperature to around 140 degrees F, but you can expect possible over temp discomfort in certain parts of certain zones (supply areas of basement and gypcrete zones). But then again, as has also been stated, "It depends".



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Gordy
    Gordy Member Posts: 9,546
    Pics

     Got some of your heat source room and piping?  Manifold stations?

    Water heater is set at 140*. what kind of supply temps. are coming off the HX?



    Thoughts are installing a mixing valve for the basement, and top floor set to proper supply temps as ME stated, and letting the staple up scream direct off the HX. Probably would have to turn the water heater all the way up.



    Marks idea no doubt is the cheapest to try. Hard to help with out visual data.



    Gordy
  • hollywd
    hollywd Member Posts: 9
    In Floor Heat

    Thanks Gordy & Mark, for all your words of wisdom. I will be installing mixing valves for all zones. It makes total sense , probably right on installer trying for the middle of all roads. Much appreciated on all your guys help, Merry X-mas and Happy New Year. Loop just thawed out and will be adjusting flow , I 've had it at 1/2 gpm .I 'll  increase  gpm slowly to see what happens No leaks , awesome ! Thanks again , Joel
  • Gordy
    Gordy Member Posts: 9,546
    edited December 2010
    Let us know

     How your progress turns out!!  Glad to hear no leaks.



    Make your adjustments slowly as to let the dwelling get equalised to your adjustments.  May take a week to dial in.



    Another thought is which zones tend to get heat calls the most, and the least. I would assume top floor middle floor, then basement. But could be middle floor top floor then basement with the staple up not performing very well. What I'm getting at is Marks advice by raising your water temps slowly you may get that middle of the road. This may allow you to get away cheaply then to install mixers on each zone, but the mixers would be the correct fix if the access allows it.



    Gordy
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Ch Ch Ch Ch Ch Changes....

    When you add the mixers, you're going to have to add a single pump per mixing zone, sized to handle only that load. Basically, this means having to completely re-pipe your system. Where abouts in the great State of Alyeska are you located? We have friends up there...



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • hollywd
    hollywd Member Posts: 9
    Great State

    Hey Mark, I live in Big Lake, 60 miles north of Anchorage. I will try and adjust heat and flow first then change things up to make it right . Middle floor works the hardest to keep up(staple up) then possibly the top floor and the bottom floor hardly calls for heat.Let me know about friends as I am interested in help with this as I am not a heating guru. Thanks everybody for all your help! I will keep you in the know . Joel
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