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I was thinking of the price for the complete setup (couple of 50-m wells, heat pump, low temperature radiators, possibly solar-hybrid with hot water). Well-collector heat pumps have much higher COPs these days: Viessmann claims up to 6-7 (but that brand is really pricey).

Pierre
by Pierre on Tue Jul 11th, 2006 at 03:27:57 AM EST
[ Parent ]
Peak COP and year average COP is quite different. You'll never get the higher COP when producing hot tap water in the summer. Also a some brands don't include the power consumed by the circulation pumps when calculating COP :(

I've never heard someone reporting a year average COP of more than 4. Still, when already at 3.5 or so, higher COPs mater less and less. The difference in savings from 2 to 3 is huge, from 4 to 5 is miniscule in comparisation.

by jkirkebo (jkk@scm.no) on Tue Jul 11th, 2006 at 04:05:49 AM EST
[ Parent ]
It's true COP doesn't matter on the power savings side, but it helps in that you can heat a bigger space with a pump of a given size (you save upfront cash on the collector, you save room in you basement, you need less of complementary heating, things like that... and also, I like the best technology, better have it in heat pumps than in sport cars !)

Pierre
by Pierre on Tue Jul 11th, 2006 at 04:21:24 AM EST
[ Parent ]
BTW, why do two 50m wells ? A single 100m is far cheaper and just as efficient. Only when one requires more well depth than the max collector length (usually 400m/1312 feet) can support it makes sense IMHO.
by jkirkebo (jkk@scm.no) on Tue Jul 11th, 2006 at 04:09:01 AM EST
[ Parent ]
Viessmann has a system of variable flow rate pumps, so they save on the flow pumps by switching off a well if it's not needed. And you have less load loss with shorter parallel fluid circuits than with a single long one. For horizontal collectors, they also have between 1-8 separate circuits, depending on the heat pump size, for the same reason.

Pierre
by Pierre on Tue Jul 11th, 2006 at 04:17:06 AM EST
[ Parent ]

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