Geothermal Cooling via Baseboard Heat Flushing?

Engineers and armchair experts, could someone run the numbers on this for me?

The water coming out of my tap is cooler than my home. If I hooked up a garden hose to the drain of my baseboard water heating system, flushed the room temperature water out of the house and into my yard, thus replacing the water in the system with fresh, cool, tap water, could I generate a significant cooling effect (thus, taking pressure of my AC unit)?

Would any heat transfer into the pipes? Would a fan on the pipes make a difference?

5 thoughts on “Geothermal Cooling via Baseboard Heat Flushing?”

  1. I agree w/ Fred. 😉

    The first thing that comes to mind is the fact that heat rises, so the air near the floor is cooler already, and it’s not moving up (through the baseboard fins) very much.

    Second, we can do some math. Who knows if I’ll do it right but let’s try…

    It takes 8.34 BTU to raise the temperature of 1 gallon of water from 39 °F to 40 °F.

    Let’s make some wild assumptions to get a ballpark estimate, all of which are probably generous.

    20 gallons in your baseboards (probably high?)
    65F tap water (I measured mine at about 70)
    80F inside temp near the floor (that’d be one hot room…)

    So you want to raise 20 gals of water by 15 F° … once the water reaches equilibrium with the room (which, I’ll assume did not suddenly cool off TOO much) that’s 20x15x8.34, or 2502 BTUs extracted from the room in that hour.

    Hum, that’s a little better than I thought. a 2-ton AC unit is 24,000 BTUs per hour, so that’s the equivalent of 1/10 of that capacity?

    But to maintain that you’d have to flush it out each hour, using 480 gals per day, you’d need some way to move air across it to actually get it up to room temp in one hour, and you’d probably need to mitigate all the condensation dripping out of your baseboards … 😉

  2. Incidentally, I just put in a 1-ton Fujitsu mini split, and it’s kept our house quite liveable on these 100-degree days. Not perfect climate controlled comfort, but pretty darned good, and it draws under 1kW when full-on (much less when partly loaded). On July 4th and the 3 days following, we used 26kWh, 23kWh, and 19kWh. Not too bad, I think – if we had days like that all month long we’d clock in at under 700kWh for the month (bad for me, but still under the annual state monthly average of 800kWh/month).

    You can see how my indoor temps are doing here: – it’s supposed to reach 100F today.

    The “main floor” temp is measured on the first floor, and the Fujitsu is at the top of the stairs on the 2nd floor. So the 2nd floor is actually a couple degrees cooler than shown, which is good for sleeping on hot humid nights…

    I need to hook up an electricity usage monitor on the AC circuit to correlate that.

    FWIW, shading the east & south windows helps a lot too. Probably simpler than the baseboard flushing approach. 😉

  3. Thanks Fred & Eric,

    I think my biggest opportunity would be in the afternoon to flush out the mid-day heat as the AC works to bring the temp down after work. Here’s some info on the operating cost of a 2-ton AC unit.

    Looks like Fred’s right in terms of savings. And, the condensation issue is not something I’d like to deal with.

  4. I’ll never do the math, but I do the following to help my energy usage out–
    –On hot days in A/C season…I only run the cold water taps to brush teeth, wash hands or veggies, etc; and I take as cold a shower as possible. This is simply to use the water heater as little as possible, and run as much warm/hot water out of the piping as possible.
    –On cold days in heating season…I only run the hot water tap for these same chores/tasks. Because I have a gas water heater that is only a year old, so it is above average efficient, and I want as much warm/hot water in the piping.

    Does it help…of course it does…does it help enough to matter…probably only to me, but that is enough for me. 🙂

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