Quote:
Originally Posted by S-F
Oh yeah. The heat pumps failed in January. Not in a mechanical sense. In a financial sense. $380 electric bill. I have never seen anything like that. Those damn things are off until it gets hot out. I guess they don't like the way I ask them to bring the house up to temp twice a day.
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Did you notice if it was defrosting often that month? I have a Fujitsu system, 8.6HSPF, heating my home with a Manual-J load of about 20k @ 15F. I keep the tstats at 70F day & night.
I don't any way to measure power consumption of only the heat pump, but my total electric usage hasn't been over $150 for any month, including a resistance water heater and lots of computer & electronic equipment that's always running.
You should try keeping them running non-stop and see what your consumption is. Running it intermittently might cause excessive defrost cycles which cause a huge reduction in efficiency. Also, a heat pump efficiency is max when the delta-T is minimal.
So, the savings of permitting heat loss at mid-day and night is countered by a loss of efficiency when it is heating with greater delta-T, especially if more defrosting occurs. We don't know the exact numbers involved so I could be very right or very wrong.
Also if outdoor temps are close to the manual-J design temps, and your heat pump capacity is close to your home's design heat loss, then leaving them run 24x7 would have them just meet your needs. Turning them on & off at these temps would push them past their capacity limits, as they can only put out so much btu/hr.
Hope you get it worked out!