View Full Version : HeatPump Aux Heat Quesitons
12-20-2008, 04:43 PM
This is my first time using a heatpump system. I am in a condo complex that houses the heatpump's on the roof and the return system in the units. I install a honeywell rth7500d so I could control the temps the way I wanted more easily. I am noticing that aux heat is used a lot even if there is a 1-2 degree difference. Is there a way to change what the degree difference should be and if so does it involve going to the unit on the roof? Also I read about a lockout temp for aux heat. Is that also located on the unit on the roof? I am trying to see if these are settings I can change or if I need to hire someone to come out and get on the roof and so forth.
Thanks for any insight!
12-21-2008, 06:29 AM
Generally, if there is a 1 to 2 degree difference, you need the aux heat to bring the temp up to set point.
Your old stat was probably not as accurate as the new one.
To lock out the aux heat, you would need an outdoor stat installed.
And I'm not sure that stat can use one.
Consult a local contractor.
12-21-2008, 10:06 AM
I did some more research and I guess a programmable thermostat might not have been the way to go with these heat pumps. It will turn on the heat pump with a 2 degree difference or more. I guess there are some out there that are actually designed to heat pumps and wont kick on the aux right away
12-21-2008, 10:45 AM
Why do you want to set your stat to say 68, and have the indoor temp drop to 65 or 64° before the strip heat comes on to keep the house warm.
Or are you setting back your temp and raising it when you come home.
12-21-2008, 07:20 PM
Locking out the aux heat above a certain outdoor air temperature is a good idea. The modern way to do this on heat pumps that don't have that capability built in is by installing an electronic thermostat that uses an outdoor air sensor. Since you mentioned reading about lockout temp somewhere I thought it might have been in the thermostat literature, but Honeywell doesn't list the model number you give. Makes me wonder if the number you list is a third party number, where a vendor has put their own part number on the Honeywell thermostat. Anyway, you will need to let a technician look at your thermostat and heat pump to determine the best way of installing or enabling an outdoor lockout. Trying to do this any other way is asking for trouble.
12-21-2008, 07:36 PM
The RTH series is a retail store model.
It is not listed in the contractors site.
But it is listed in the home owners site.
12-21-2008, 09:57 PM
Went to the homeowners website and read the literature. This thermostat doesn't support outdoor sensing. I like the idea of replacing the new thermostat with another one that can use an outdoor sensor. That way the homeowner could use trial and error to determine the lowest temperature the heat pump alone will heat the home. Of course, no one knows if the heat pump being discussed already has a lockout that just needs adjusting. On another note, I was amazed to learn that Honeywell is offering DIY products. I don't work residential anymore. But when I did, it happened regularly that I had to tell a homeowner that the new thermostat or whatever they just installed wouldn't fix the problem. The money and time spent could have gone quite a way toward paying for the correct solution.
12-21-2008, 10:11 PM
They been selling to DIY for many years now.
Its a market they make a lot of money from.
12-22-2008, 09:25 AM
I connected all they wires from my analog thermostat correctly to the new digital one. That's why I would assume everything would continue acting as normal and I would just have more timing options and so forth. Yes my goal was to do a setback overnight and during work. Like 63 when I am gone and 68 when I am home. If it's within a 5 degree difference I would like the heat pump to come on and try to make up the 5 degrees instead of immediately relying on the aux heat.
This is my first winter in this condo so I didn't get a chance to play around with how the analog one worked, if it brought the aux heat on as well with a 2 degree diff. I am concerned about the lockout because if the temp outside is say 40 and up then the heat pump should be enough, I don't want the aux coming on all the time when I bring the house up to temp.
You are most likely right that I should just hire someone to come out and check the settings on the unit it's self.
I did have one wire left over from the old stat. It was the thermostat wire or something like that "T" was the letter and it went I believe to the slide bar. Websites I read say to just tape it off and it isn't needed in the new digital ones, so hopefully that isn't messing anything up by not trying to connect it somewhere.
12-22-2008, 12:12 PM
Your anolog also brought the aux on when there was a 2 or more degree difference.
Powered by vBulletin® Version 4.2.0 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.