Doug wrote:
On Wed, 10 Oct 2007 23:31:20 GMT, "Pete C."
wrote:

dpb wrote:
Pete C. wrote:
"Not@home" wrote:
...

My understanding is that heat pumps are more efficient, but need a
supplementary source of heat in areas where the winters are quite cold.
Air source heat pumps need supplemental (usually electric resistive)
heat in cold areas. Geothermal / ground source heat pumps don't since
their coils are below frost lines and soil temps are stable.
I'd revise that slightly as geothermal / ground source heat pumps _may_
not if sufficient heat source/sink capacity is available since
their coils are below frost lines and soil temps are relatively stable.
I'd revise that to "a geothermal heat pump with a correctly sized ground
loop" since in stable 55 or so degree soil a properly sized loop will
always be able to extract sufficient heat.

Aye, there's the rub.

Here in Connecticut where the frost line in mid-winter can easily get
down 40 to 48 inches, to get to that 55 degree point means burying
everything down at least 6 to 8 ft. That's pretty costly and sometimes
impossible here in New England with its bedrock and rocky soil....

Ayup. I'd think it would be even farther down than that to get 55F
year 'round. That's where the alternative to a well source begins to be
potentially attractive if there is a water table.

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