# Programmable Thermostat and Aux Heat



## wahoowad (Nov 8, 2006)

I installed a programmable thermostat this Fall for my heatpump. I more or less accepted the default schedule as it fit my daily schedule fine. I notice the aux heat (resistance coils) kick in a lot when the heatpump first comes on. I assume this is due to the temperature differential between the initial warming air the heatpump creates and how cool it is in the house. I see no way to control this in the thermostat. Somehow the thermostat is making a calculation and determining when to kick in the aux heat. I'd like to lower this threshold if possible to keep it from kicking in as often. It almost seems to do it every time it comes on.


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## pgmr (Nov 8, 2006)

Our Bryant Evolution dual fuel system did the same thing.  Heat pumps just don't recover quickly enough to satisfy the stat, so it brings on the aux heat.  Since our aux is gas and the price of gas has gone up so much, I have given up on setback for the time being.


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## Sandor (Nov 8, 2006)

Your certainly losing the benefit of a programmable thermostat.

Most thermostats have a setting that dictates when the aux heat runs, usually 2 degrees. So if its very cold out, and the heat pump cannot keep up, the aux will engage. This makes no diffence to those who use oil or gas as primary heat.

Now, go back and read the directions to see if that is adjustable. I got frustrated years ago because I had the same problem as you, and could not make the thermostat let the heat pump run, without engaging the aux. So, if you set it for 62 overnight, then programmed it to 70 at 5am, the aux would run until the house temp hit 68. No way to save!

A workaround is to reprogram it to slowy bring the house up to temp in increments of 2 degrees. 

3am 62-64
4am 64-66
5am 66-68

If you post your make/model and they have online directions, I look through it for ya.


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## wahoowad (Nov 8, 2006)

Thanks, Sandor, you give me hope that I can keep that expensive aux from kicking in Woohoo.

I think this is the one I have http://www.lowes.com/lowes/lkn?action=productDetail&productId=183786-74493-183786&lpage=none


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## Sandor (Nov 8, 2006)

wahoowad said:
			
		

> Thanks, Sandor, you give me hope that I can keep that expensive aux from kicking in Woohoo.
> 
> I think this is the one I have http://www.lowes.com/lowes/lkn?action=productDetail&productId=183786-74493-183786&lpage=none



Need your model number, not the Lowes number. Here's the directions on how to find the Honeywell model #. 

http://yourhome.honeywell.com/yourhome/Applications/FindModelNumber/ModelNum.aspx


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## wahoowad (Nov 9, 2006)

Honeywell RTH7400D


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