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Geothermal heating cooling
I'm surprized Ken wasn't taking bets on how long before I put my $0.02 in on this one.
I have designed a decent number of geothermal systems, but will admit to rather limited experience with horizontal installations. What I have seen, read in the trade, and learned from trying to help Ken strongly suggests sticking with known, independently tested ground exchanger designs.
Ken's contractor had a home brewed concept with no 3rd party test data to check it against. I think Ken got short changed, but can't prove it. It also seems like the unit may be a little small for the house and climate. Recovery time is a function of unit size vs. load.
Add some hardware issues with what was a new technology at the time (2 speed compressors) and I don't blame him for being bitter. I really would have hoped Waterfurnace would have stepped up to the plate on the equipment side, but apparently they haven't.
It's a lot like the discussions we keep coming back to here about tractors and dealers. Usually any of the name brand machines are fine to own, but having a good dealer and in this case a good installer very important.
If you have the room to go horizontal, be sure to spread it out, get it all in as deep as possible and limit the number pipes in one trench. The whole concept is transferring heat to and from the earth, so keep the pipes away from each other. If you can do your own trenching, I wouldn't even consider any more than a 2 pipes / trench design. Spread the trenches at least 25 feet apart if you need multiple trenches, and keep everything at least 4 feet down. That's how to have an efficient system.
In extreme climates, either very heating dominant or very cooling dominant, the system efficiency will go down compared to a nicely balanced load. A correctly done ground exchanger design should take that into account.
If you have cheap fuel available (oil, gas, propane) don't even consider geothermal. But if you are stuck with electric, and want to invest some money now to save it later, it may be worth looking at.
I consider ground water too precious a resource in most areas to think about an open system, but they have a lot of advantages in first cost and constant temperature if you have the water supply. Looking at run time the well pump life may be normal. Think of how much the pump run time changes if you use a couple of gpm / ton the whole time the unit is running.
Geothermal isn't a cure all technology. But it can be a good technology when correctly applied. Get an IGSHPA certified designer and installer and be sure they stick to a proven design. Also, be sure they don't undersize the equipment. An undersized AC unit can't catch up in a heat wave either.
More than enough said.
- J Parker
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Geothermal heating cooling
Check into local drilling prices for a vertical closed loop system. That's all we do commercially. You're right, I don't think in areas with a deep frost line that you can get a horizontal down deep enough to really be worthwhile unless you put in a lot of pipe.
Still it's more efficient to pull heat out of 35 degree water than 5 degree air.
- JP
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