What is "aux. heat"?

CTho9305

Elite Member
Jul 26, 2000
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My heater started making a strange noise yesterday, and I saw that the "aux. heat" on the thermostat was flashing (the noise was happening at about the same rate as the flashing). the heater uses an outside heat exchanger. Is this a problem?
 

MSO4

Member
Oct 21, 2001
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What type of heating system do you have?
IS it gas, electric, heat pump, what???????
I used to work for my dad who has a heating and a/c company, so i learned alot from him.
The "aux" light could be refering to an emergency heating device to help maintain temperature in your home. It helps out the primary heating system, when it fails to keep up with demand.
The noise should be checked, I have a feeling it is trying to come on but is not able to, and that is what is causing the noise. The light could be flashing to signal it is trying to come on but goes off when it fails to come on.

If this is the first time this is happened , is it colder than usual?
might be too cold for your present heating system, just a theory though.

recommend you get it checked out!
 

Amused

Elite Member
Apr 14, 2001
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A heat pump works in the same way an air conditioner does, except in reverse. It draws heat energy from outside and concentrates it inside.

(ever notice how a window air conditioner blows more heat out the back than cold out the front?)

Now, if the heat pump can't keep up, or if your thermostat is turned up past a set number of degrees from the ambiant temp, "Aux heat" gets turned on. This is usually some electric coil elements. Though it could be gas burners too.

Heat pumps work with the outside temp down to about 45-50 degrees, any lower, and they have to rely on aux heat.

Also, heat pumps have a problem with the outside coils getting iced over. When this happens, it reverts to AC mode to heat the coils and melt the ice. To keep from freezing you out of the house, it kicks on the aux heat.
 

CTho9305

Elite Member
Jul 26, 2000
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thanks for the replies. I dont think aux heat is emergency heat - there is "em heat" which does something internally. I'll have it looked at.
 

Amused

Elite Member
Apr 14, 2001
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<< thanks for the replies. I dont think aux heat is emergency heat - there is "em heat" which does something internally. I'll have it looked at. >>



Emergency heat and aux heat are basically the same thing. Emegency heat is simply aux heat on high.
 

Sluggo

Lifer
Jun 12, 2000
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It all depends on the system you have. Around here when a heat pump is used, the "Aux Heat", or "Emer Heat" generally refers to the gas fired furnace that is more efficient than electric heat at lower outside temps.

Of course most people will argue that a gas fired furnace is always more efficient or at least more comfortable since it blows out higher temperature air from the vents. The people down at the electric company will argue that a heat pump is more effifient at certain ext temperatures than gas fired furnaces, which may be true, but most people prefer the "feeling" of a gas fired furnace.