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oldswab 12-02-2009 09:28 AM

heat pump cut off set point
We have a new Carrier Performance 5 ton heat pump, a 2200 sq foot home with lots of glass, and live 50 south of Indianapolis. The new heat pump and ultra high efficiency gas furnace (also Carrier) were installed in October. This is my first experience with a heat pump but we had a high efficiency Carrier gas furnace for 22 years before this new installation.
The heat pump seems to lock out and the gas furnace aux heat come on below about 30 degrees, but as soon as the inside temp recovers to 70 (we set it at 60 at night) the heat pump seems to kick in again. Hasn't really been cold enough during the days yet to see if the heat pump stays off when day time highs stay in the 20's. So my question is, given the price of natural gas, would it be more economical to select emergency heat when outside temps get below 30 and thus lock out the heat pump and rely on the gas furnace? I'm assuming that in the emergency heat mode that the heat pump does not operate, right?

hennyh 12-02-2009 01:30 PM

If it's a brand new system you should be asking your contractor for the optimal lockout settings based on his experience with temp conditions and energy costs in the area.

In general, a 30 degree heat pump lockout temp seems way too high unless electricity is super expensive and natural gas is cheap. I wouldn't be looking to set HP lockouts until you're in the low twenties.

beenthere 12-02-2009 01:35 PM

That would depend on your gas and electric rate.

Nope, once set to emergency heat, the heat pump doesn't run anymore.
Sounds like they really oversized your heat pump.
What brand and lodel thermostat are you using.

oldswab 12-02-2009 02:04 PM

thermostat info
The thermostat is a Carrier seven day programmable. I was wrong about house square footage, more like 3200. My wife is a realtor and keeps track of that stuff, I try to keep the machines running. :)

beenthere 12-02-2009 02:09 PM

5 ton for 3200 sounds better.

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