geothermal hydronic questions

BC_7

I'm in the middle of just such a retrofit and so far it's working out great ($3500 ahead to date on heating bill this winter). I'm using a combination of radiant ceiling, floor, and panel radiators. The panel rads work fine, but at the water temps in a geo system they only put out about 30% of their rated output so they need to be pretty big - my kitchen is using a 2'x6' and a 3'x5'. The two rooms I have radiant ceiling in are very comfortable - I'd recommend this approach over underfloor since it is easier to retrofit and you can generally run lower water temps compared to underfloor.

40btu/ft2 at 115F water temp sounds optimistic to me for underfloor unless you're using extruded plates with very tight spacing. Others with more experience can probably confirm if that's a reasonable expectation. Also keep in mind that the 115F is a max temp - lower is always better for efficiency and longevity.

Climatemaster has a hydronic heating-only unit that they claim can do 140F reliably - I have no experience with them but I think their reputation is good. That might be enough to run your baseboard maybe with some additional radiators. Have you figured your heat loss yet?

realolman

Hydronic geothermal

I have been in touch with a local contractor re: converting my existing house over to geothermal hydronic heat. I have a few questions.

He said the most I could get from radiant under floor was 40 btu / sq ft of floor... if there is carpet, 20 btu / sq ft. Does that sound correct?


Are the radiant panels like those made by runtal suitable for geothermal radiant heat? How would they compare in price to in floor radiant, considering I already have baseboard heat?

He seems to favor hot air ducts over hydronic. I know there are some advantages to that, but I want hydronic.

I guess I'm afraid that he seems to have a cut and dried package that he puts in every house.... Perhaps that approach might end up being correct in every case, but I wonder if there's something lacking that results in treating every house the same.

I don't know many around here who have done this retrofit, but the one I know was $30,000. ( hot air ducts installed where there was an existing base board system ). That seems pretty steep to me. In the area I live, I don't think I'll have a lot of choices in people who know this stuff.

I think I'd feel better doing it myself. At least I know I wouldn't be treating everything like a nail because the only tool I care to use is a hammer.

troy_8

geo-radiant

You are right to question. I will only do geo in combination with hydronics. Geo to air leaves a customer that is used to hydronics feeling COLD due to the cool air delivery temps. Granted it will heat the house but the blowing of cool air doesn't lead to much creature comfort. Flat tube radiators are an excellent choice and generally less expensive than a radiant retrofit. You can use your existing baseboard for heat emitters but you will probably have to double the length. I design for 115deg. water temp.much lees I'm sure than what your system was designed for.

realolman

Im not

all that interested in using the existing baseboard... in fact I hadn't even considered it. But the contractor's talkng about running hot air ducts everywhere, and I thought: well, I have the piping for the baseboard... maybe replace the baseboard with radiant panels? This is a retrofit... doen't that seem reasonable?


Also, my wife is adamant about not wanting hot air and is not at all sold on the return on investment.

Although I do think getting away from fossil fuels, and doing your part to help decrease pollution is worth something, she does have a valid point. It does need to be cost effective to some degree.

Bob Gagnon plumbing and heating

Keep the baseboard

and use it as a supplement to the geo or use it with your geo for heat delivery along with radiant ceilings or walls. I was suprised how comfortable radiant ceilings were when I installed them in my house. I use it with low temp solar heat, but low temp geo heat would have similar results. Sheet rock is a great way to deliver low temp heat because it doesn't hold the heat back like wood subflooring does. If you heat a 1st floor ceiling or an interior wall you would have no heat loss like you would on a 1st floor underfloor system. Even with good insulation you would lose some BTU'S downward to the basement, with renewable energy every BTU is valuable. Thanks, Bob Gagnon

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realolman

Boy,

there's something I really hadn't thought of, but I think I might like it a lot. What about an entire interior wall with pex loops fatened to sheetrock?

Unknown

doable

I've done a couple of geo retrofits using panel rads, and they've worked quite well. As mentioned earlier they must be sized for the low water temps you are using, I used 110 as the design on the last one, here is a datasheet for the ones I usually use with a conversion chart on page 6. Yes I know it only goes down to 122, some quick figuring will tell you the factor to use for 110, I think I was using .25 at a 10 degree delta T.

Biasi Concept Plus

Bob Gagnon plumbing and heating

An interior wall

or ceiling, in the master bath or near the living room couch would put more heat where you need it. If you run it with your boiler you could run lower temps making your system more efficient. Or you could have a separate zone for the living room and bath and just run that in the spring and fall when you don't need too much heat. Then if you go solar or geo in the future you have a separate system to deliver that energy. Thanks, Bob Gagnon

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Unknown

radiant ceiling is the cheapest way to reliably utilize geo temps in most homes, IMHO. Panel radiators second, with baseboard properly sized, then radiant floor.

of course, comfort ranking is often more like floor, ceiling, radiators, baseboard.

Geo itself is very expensive though, don't expect cheap in any case.

realolman

thank you

very much for that.

They sure look a lot like the old radiators I have in my basement ( much nicer looking though )... Couldn't those be used instead of the radiant loops overpoured in the basement? Sure they might not be as nice and I really am not looking to do anything on the cheap, but I don't want to throw money away or raise my floors when something else might work well with what's already there ( the piping).

Bryan_16

WHERE ARE YOU

located?