Quote:
Originally Posted by DonT
they about 24' apart. that's farther apart then they should be, but with the high water temp it's about 85f to 90f and I have the flow almost shutoff. I have a single zone system
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DonT,
That spacing does not look at all good for your GSHP.
The heat exchange from any GSHP heating system relies on temperature difference (AKA: delta-T) times the area of the transfer surface, PEX-to-concrete in your case.
Your delta-T will be very low compared to what would be assumed for fossil fuel. Maybe half the delta-T. As has been mentioned, a GSHP can heat water to 130F but that is the very top of its range. For real efficiency (and that is what you really want) from a GSHP system, you want to keep the water temperature much lower, like 110F or even lower. To do that, you need to drastically lower your heat loss, by insulating.
And
your PEX-to-concrete area is very low even for fossil fuel temperatures, about half of what I have seen in most fossil fuel PEX layout designs. Are you ready to demolish your existing floor and put in another one with much closer PEX spacing?
{* Low temperature heating PEX spacing runs about 6 inches. *}
So if you want to do GSHP, you will need to insulate your place to a far higher level than it is now. Much higher than is common for fossil fuel heating, and much higher than for typical GSHP heating because your spacings are so wide.
Just a seat of the pants guess would be at least 4 times greater than it is now. That is based on how much heat you now require, using your present insulation level.
Quote:
Originally Posted by DonT
I should have said this earlier. I just built my 3 years ago. at the time I insulated it very well. The ceil is 2 inch of closed cell spray foam with R13 fiberglass covered with 3/4in knotty pine boards. That's about R25 to R30, (would have put in more but ran out of room). The walls are 1 1/2 in foam board with R21 fiberglass with 3/4in knotty pine boards, that's about R25 to R30. The floor has R13 fiberglass, cover with 2in foam board so that's about R25. Yes I have a few areas the could use a bit more insulation and I intend to do that a sometime.
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Thought I'd throw this in. It's the required insulation level in your state. Actually this is for Zone 7, the state just above you, but the numbers are all the same except for floor, which in your case will be heated. These are not extreme insulation levels, they are what all new builds are suppose to have.
In your case, if you want to do GSHP heating, with the concrete slab such as you have, you must go
WELL BEYOND these levels.
Best,
-AC_Hacker