Why is "Auxiliary Heat " on instead of regular Heat?


Old 12-29-10, 08:36 AM
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 2
Question Why is "Auxiliary Heat " on instead of regular Heat?

I have a Honeywell Digital Thermostat that was installed by a professional HVAC man and Electrician back in 2009. While we have had very cold weather here in FL, I never had this prblem last year. It was cold then as well.

When I set the thermostat to heat at 72 it shows that it is on Auxiliary Heat (not Em. Heat) and it takes forever to heat the house. I only have an 1100 sq ft. home, so it isn't like it is a huge house. The AC unit is a 1992 - 2 Ton Gibson. It is older and noisy, but the AC guy cleaned it, including all coils and corrected the freon charge/fill, and up until now, I have not noticed any issues. Any suggestions or clues as to why Aux. Heat is showing?
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Old 12-29-10, 12:21 PM
Join Date: Feb 2005
Location: Southeast USA
Posts: 1,067

you are certain you have HP? assuming so, at low outside temps where heat pump can not maintain inside thermostat setting, heat strips will activate along with the outside heat pump condenser operating to help boost heating BTUs needed. This is called auxilliary or supplemental heat . Keep in mind, heat strips are used to supplement heat as well as to temper incoming air when HP condenser is running a defrost cycle. Heat strips are also used as emergency heat alone when there is a malfunction to outside condenser.

The idea that "it takes forever to heat the house" raises a question about system operating correctly. It could be your thermostat is calling for aux heat and you are getting a false reading that the heat strips are operating as they should be.

Are you certain you even have the heat strips? If so, take a digital thermometer and get a reading of supply temp when thermostat shows auxiliary is working. Also take a reading using emergency heat only.

Beyond that and seeing the posted results, I can not be sure whether you have an issue or not.

when was last time system was serviced? a system this old should be serviced at least yearly for proper and reliable operation.

Old 12-29-10, 12:32 PM
Gunguy45's Avatar
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Join Date: Dec 2007
Location: USA
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No Pro....but it's possible the checking/correcting of the charge concealed a leak...or even caused one. You may be running on heat strips only.

When was the service done?
Old 12-30-10, 06:07 AM
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Join Date: Dec 2010
Location: USA
Posts: 2
To Both Gunguy and Tigerdunes, Thank you for your response! The service of the unit as well as the thermostat install was done in August of 2009. We do have heat strips, but they are only the 5K and not the 8-10K that the AC guy recommended. We know we need a complete unit, including new air handler, but it is just not in the budget at this time. We just had the complete roof replaced at a cost of $6400 as we needed 52 sheets of plywood! I had my husband take a look at it, and once the outside temp got into the upper 40's, it changed itself over from Aux heat to regular. A few weeks ago I made the mistake of turning on the EM Heat, which runs non stop and never turns off. At least with the Aux Heat, it will eventually turn off once it hits the desired temp. I guess it is working properly since it knows to switch to regular Heat when the outside temp gets warmer. We have been on the low 20's to upper teens here in FL, so I am sure the unit itself is just not able to handle it. I was wrong about the make, it is a Goodman, not Gibson. Anyway, I thank you both very much!
Old 12-30-10, 11:57 AM
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Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
5kw Aux heat is not much, so that's why when you had it in emergency heat, it ran non-stop, where when you had it in heat mode, the HP and Aux heat worked together, it was able to cycle as needed.

Everything seems to be working, so no worries.

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