aux heat question

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Old 10-17-05, 05:22 PM
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Exclamation aux heat question

I just installed a programmable thermostat and just ran the heat for the 1st time. I noticed that if room temperature drops 2 degrees below the tstat setting then the aux heat comes on. Is this normal? If its only a 1 degree difference then just the heat pump is on. Is there any chance the aux heat is coming on with the heat pump everytime and its not showing up on the t-stat? I check the unit outside and the fan is on blowing cold air, and the freon line that runs to the unit is hot?
 
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Old 10-17-05, 05:45 PM
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You got it right there on the heatpump. Thats how they work. When the tstat is set and it turns on the heat only the pump should run. Now when the pump cant keep up to heat the home and it drops that 2 o then the strips should turn on. This is why we dont use some of the new tstat that are programmable. When you set it back and the home cools down some .Then it turns back on to bring the heat up it turns on the strips also . So you lost what you saved on the set back. Some real good tstats for the heatpump will work the temp back up slow and not turn on the strips. If your new to heatpumps you might see it on fire the first time you see it go into defrost. Thats just the steam from the frost on the coils out side is all .

ED
 
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Old 10-17-05, 06:04 PM
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Thanks for the reply. I just wired a new tstat that is programmable but is able to bring the heat back slowly. I think I just want to make sure the aux heat isnt coming on everytime. The tstat doesnt show they are on but the register seems pretty warm for just the heat pump. I dont think the wiring was a problem. It was almost identical with the old.

honeywell t8411r(old) honeywell rth7400(New)
R R
w2 w2/aux
g g
y y
o o
c c

The old tstat had a jumper from y and w1.
The new tstat has a jumper from r and rc. I was advised to also run a jumper from w2/aux to E.
 
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Old 10-18-05, 12:50 PM
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If you program it to setback more than 2 when it comes back up the aux will kick in everytime. In the winter just set a heatpump at one temprature and leave it.
 
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Old 10-18-05, 02:02 PM
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I just read that this is the old theory that the heat pumps should NOT be set back when you're away. They say with the new and improved thermostats that are designed specifically for heat pumps you can vary the temperature.

The manual to my heat pump thermostat has a sample schedule inside and they vary the temperature by 8 degrees from 70F when you're at home (heating) to 62F when you're away.

I was wondering myself if this is the optimal temperature difference, but decided to try going the manual. Does anyone have any experience with modern heat pump setback thermostats that can support or disprove this?

My aux heat is natural gas and considering that this winter the cost of gas will go up 60%, I am very much interested in knowing what is the MOST efficient set up.
 
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Old 10-18-05, 03:54 PM
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You might want to go to http://www.warmair.net and compare fuel cost.To see what one you want to use the most. Might be you can lower the cut in temp for that gas furnace there more or run the heatpump to a lower temp.

ED
 
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Old 10-19-05, 05:51 AM
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I have the cheapest digital TStat you can buy.
It is not programable but it lets me set points where it calls for Aux heat.
It was set from the factory at 1 degree, but I adjusted mine to 3 degrees.
Now my Aux heat only comes on when it needs to help the heat pump, Rather than coming on right away.
I inquired to my AC guy why the threshold was set so close and he told me it was setup for comfort, not energy saving. It did lower my electric bill, but not enough to preach about it.
 
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