Quote:
Originally Posted by cholcombe
I've really learned a lot reading this thread...
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Another consideration when sizing your ASHP, when the outside temperature goes down, the amount of heat output that an ASHP can deliver also, unfortunately, goes down. This is different from a fossil fueled heat source or a ground source heat pump.
I generated a chart, based on
some data that Xringer dug up, that should suggest this situation:
...so when the weather gets colder (and you need more heat), the ASHP has less heat to give.
So if your design temperature was for instance 16 degrees F, and you did a heat loss calculation and therefore knew you needed say, 12000 BTU to do the job, you wouldn't go for a 12,000 BTU unit, you'd need to go for an 18,000 BTU unit, because that would be the closest to do the job at 16 degrees F.
This would be adjusted for the reduction in efficiency as the outside temperature gets lower.
Regards,
-AC_Hacker