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Old 01-14-2010, 08:24 PM   #1
knarf
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Default Aux Heat Light on Thermostat Not Working

High all, this is my first time on the Garage Journal and was wondering if anyone could offer some advice. I have a Heil 2 stage heat and 1 stage ac, heat pump unit. Everything seems to be working properly except the indicator lights on the thermostat.

If I switch the thermostat to emergency heat the red emergency light and the blue aux light both come on (the blue aux light about half as bright as the red emergency light). When the thermostat is in the normal heat position and I raise the temperature high enough so that both mercury bulbs are engaged (if I understand correctly this kicks in the aux heat) no lights come on. The heat from the registers is greater when both mercury bulbs are activated so the aux heat strips must be working. I would like to know when the aux heat is on without having to remove the thermostat cover.

Does this sound like a defective thermostat, or wiring problem, or something else? The system was professionally installed in '04, but, I just noticed this situation with the cold snap we have had in South Carolina since the first of the year.

Thanks,
Frank
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Old 01-14-2010, 09:35 PM   #2
rickairmedic
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Default Re: Aux Heat Light on Thermostat Not Working

Frank that is an OLD thermostat . generally the aux heat will only kick on if you raise the temp at the T-Stat over 5* over the current temp showing on the T-stat or when it gets cold enough outside to cause it to kick in usually under 40* outside air temp .


Rick
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Old 01-14-2010, 09:53 PM   #3
knarf
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Default Re: Aux Heat Light on Thermostat Not Working

Thanks for the feedback Rick. The top mercury bulb does engage about 5* above where the lower bulb engages so the top bulb must control the heat strips. I just can't figure out why the aux light does not come on, its not burnt out b/c it comes on when I turn on the emergency heat.

Frank
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Old 01-14-2010, 10:06 PM   #4
rickairmedic
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Default Re: Aux Heat Light on Thermostat Not Working

Hey Frank no problem and by the way Welcome to The Garage . The Aux light may not actually be comming on you may just be getting residual light though it from the Emergency heat light . That Thermostat is pretty old though . They dont even make T-stats with Mercury bulbs in them anymore.


Rick
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Old 01-14-2010, 10:14 PM   #5
jkeyser14
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Default Re: Aux Heat Light on Thermostat Not Working

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Originally Posted by rickairmedic View Post
Hey Frank no problem and by the way Welcome to The Garage . The Aux light may not actually be comming on you may just be getting residual light though it from the Emergency heat light . That Thermostat is pretty old though . They dont even make T-stats with Mercury bulbs in them anymore.


Rick
I just had a new geothermal system installed and it has mercury bulbs (or at least the manual that came with it had a warning about mecury inside). As far at the light goes, my system has the option to turn the aux heat light off in a hidden settings screen.
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Old 01-14-2010, 10:56 PM   #6
knarf
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Default Re: Aux Heat Light on Thermostat Not Working

Since this thermostat seems to be an antique, how difficult is it to change one out say to upgrade to a basic non-program digital unit? Are these things specific to a particular brand of heat pump or can I go to a home store and pick up a replacement, should this only be done by a professional?

Thanks,
Frank
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Old 01-15-2010, 12:03 AM   #7
rickairmedic
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Default Re: Aux Heat Light on Thermostat Not Working

Frank you can change it out to a digital programable ooor non programable . You need a T-stat desighned for heatpump systems . I recomend Honeywell only if shopping at Homie desperate or Lowered expectations . I will see if I can get you a link for Home depot Lowes isnt showing a Honeywell that will work for you and Home depots website is down for maintenance right now. Swapping out a T-stat really isnt rocket science honestly . You need to kill the power to the air handler first so the 24 V is not being sent to the T-stat after that its really just a simple matter of removing the old one ( making note of what letters what wires are hooked to ) .Generally it is R=red,W=white , G=green , Y=yellow but with heatpump units there are some extra wires to control things like the Aux heat and the reversing valve . The reversing wire will either be O=orange or B=blue depending on the system you have generally O is energised in the cooling mode and B is energised in the heating mode . What brand system do you have .

Rick

Last edited by rickairmedic; 01-15-2010 at 12:07 AM.
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Old 01-15-2010, 09:54 AM   #8
knarf
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Default Re: Aux Heat Light on Thermostat Not Working

A sticker inside the t-stat cover says Heil model haxc004tw01, htg .15 to 1.2 AMP, clg 1.5 AMP max. By the way Rick, I ment to comment that you might be exactly right that the Aux lamp could be defective or missing and the dim illumination may actually be from the emergency bulb, good catch. As you can see from the picture I have to go a little deeper to check that out, but, now I am thinking if I have to remove the t-stat from the wall why not just upgrade it. You said to, "[K]ill the power to the air handler first so the 24 V is not being sent to the T-stat[.]" How is this usually done, from the fuse box or somewhere inside the heat pump unit? My condenser, filter, and blower are inside the house in the wall, there is also a fuse block with a disconnect near the fan unit outside, I have a mobile home.


Frank
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Old 01-15-2010, 10:03 AM   #9
rickairmedic
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Default Re: Aux Heat Light on Thermostat Not Working

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Originally Posted by knarf View Post
A sticker inside the t-stat cover says Heil model haxc004tw01, htg .15 to 1.2 AMP, clg 1.5 AMP max. By the way Rick, I ment to comment that you might be exactly right that the Aux lamp could be defective or missing and the dim illumination may actually be from the emergency bulb, good catch. As you can see from the picture I have to go a little deeper to check that out, but, now I am thinking if I have to remove the t-stat from the wall why not just upgrade it. You said to, "[K]ill the power to the air handler first so the 24 V is not being sent to the T-stat[.]" How is this usually done, from the fuse box or somewhere inside the heat pump unit? My condenser, filter, and blower are inside the house in the wall, there is also a fuse block with a disconnect near the fan unit outside, I have a mobile home.


Frank

Frank alot of indoor units have breakers on them ( heat pump air handlers ) if yours doesnt just flip off the breaker in the main breaker panel.


Rick
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Old 01-15-2010, 10:12 AM   #10
knarf
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Default Re: Aux Heat Light on Thermostat Not Working

Rick,

I forgot that it was there, right under the blower in the sheet metal is a breaker. Thanks for the help, think I'll try a swap-out.

Frank
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