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Garage zone consideration when lowering temps

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HelpInAK
HelpInAK Member Posts: 41
I’m in the process of installing extruded plates with my shoddy staple-up system in the house (about 1/3 the way done - laborious process) to lower mod-con operating temps. I’m planning on just slowly lowering SWT until it can’t keep up with set point. I haven’t put much thought into the garage slab zone - is there anything I need to adjust (mixing valve, circulating pump speed) to keep that zone running smoothly?

Related question- can anyone please explain how the garage zone water temp is what it is - my SWT is currently set to 160. The temp gauge after the mixing valve/circulating pump for the garage zone reads about 80-85 when answering heat call. Return water temp on the boiler is 150. From my (probably wrong) understanding is that the mixing valve is recirculating some of the cooler returning water with the supply water to lower temp of water entering the slab, but if that were the case that temp should be somewhere between 160 and 150 and not 85. How is the water entering the slab so cool?

Thank you!

Comments

  • neilc
    neilc Member Posts: 2,707
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    did you diagram your pipe arrangement in your other thread?
    can you post that here?
    maybe the garage is getting what's left of the tempered water heating the house (lowered return water)?
    how many mixing valves and or circulators?
    known to beat dead horses
  • HelpInAK
    HelpInAK Member Posts: 41
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    I’ve attached a picture of the arrangement. The right hand side mixing valve and pump is the garage zone. The only other mixing valve is for the DHW and circulating pump for house zone
  • neilc
    neilc Member Posts: 2,707
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    2 loops or 4 to the garage?
    if 2, how is water returning if on that one manifold?
    if 4, well, where is other manifold and return?
    I don't see how your forcing flow to the floor.
    known to beat dead horses
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    Flow to garage is the right hand circ pumping out of the mixing valve.

    I'm not sure what your question is.

    A mixing valve has it's own circulator so its its own unrelated loop. Most of the flow is simply recirculated in the garage loop. So the 85 degree return temp is not much flow. The majority of the return to the boiler is the higher temp from the house zone. Or, the boiler loop is higher than the secondary loops resulting in high boiler return temps, and lower efficiency.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    Is that all 3/4 pex? Some repiping in copper or iron of appropriate size would be an improvement. It does look to be piped correctly, pumping away and closely spaced Ts for pri/sec the boiler must have it's own internal circulator.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • HelpInAK
    HelpInAK Member Posts: 41
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    @neilc 2 loops to the garage. The 2 straight pipes are outgoing, 2 returning are coming out of garage at slight angle, I think the angle of the picture makes it look like they are on the same manifold, but they are separate.

    @Solid_Fuel_Man I guess what I’m asking is if I lower SWT down to 140 or lower should I expect the garage water temp to lower accordingly or will it self regulate to stay around 85
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    It will still stay around 85. As long as your SWT doesn't drop below approx 95 you will stay at 85 in the garage.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
    HelpInAK
  • neilc
    neilc Member Posts: 2,707
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    ok, I see the 2 loops now, trick photography gets me every time.
    you basically have it right in your op,
    your mission is to finish with the transfer plates, and dial the ODR down as low as you can
    known to beat dead horses
    HelpInAK