Heat pump troubleshooting

noname87 · 2011-01-19T20:32:23+00:00

My last heating bill was excessively high and I am trying to figureout what is going on.I have two heat pumps. The first unit is a 3 ton Goodman (seer 13)that produced a delta T (air duct outlet temperature-inlet ducttemperature) of 20 when the outside temperature was 52. The secondunit is a 2.5 ton Goodman (seer 13) which produced a delta T of 24.Do these number make sense. What temperature rise should I expect atthis outdoor temperature? I would expect the units to be efficentunder these conditions. I am well aware that at low temperatures theefficentcy drops.Thanks for the help.

Jan 19, 2011 23 Replies

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trader4 15 years ago

Also thermostats differ in how programmable and flexible they are. Take a look at a Honeywell VisonPro TH8320 installation manual as an example.

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IMO, SRN's posts accurately describe what's going on. As he pointed out, while a heat pump's efficiency drops as the outdoor temp declines, even at 25 deg, a decent one is still producing over 2X the heat you'd get using resistance heat. So, the advice to go to 100% aux heat makes no sense to me, unless you want an even higher bill.

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Mark 15 years ago

While I agree with you in theory but at 25 deg F, not in practice.

In theory, the heat pump will cost less to operate, but in practice at

25 F the heat pump cannot keep the house warm and it runs full time. So you have to take the wear and tear cost into account. How much does it cost to replace a compressor? Also if it is icing up and the defrost cycle has to run every 1/2 hour, it just doesn't make sense to run the machine any longer.

Mark

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trader4 15 years ago

I guess when it gets cold here and the furnace is running most of the time, I should shut it off because I'll wear it out. If you amortize the heat pump cost over it's entire life and factor that in to the cost of operating it, I'm sure you'll come out ahead compared to using electric resistance heat, even when it's 25F. At that temp, you're still getting 2X the heat for every $1 of electricity. How many hours of that do you think it takes before you've paid for the heat pump?

If it's in an environment where it's defrosting that frequently, then yes, I agree that's an issue.

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