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Honeywell Thermostat to Hunter 44668 Thermostat (2 wire, AC wired into furnace)

Honeywell Thermostat to Hunter 44668 Thermostat (2 wire, AC wired into furnace)

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Old 06-17-11, 05:50 PM
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Honeywell Thermostat to Hunter 44668 Thermostat (2 wire, AC wired into furnace)

Alright, I have a mobile home that I have been completely remodeling. I am a jack of all trades myself with the exception of HVAC. I have an Intertherm Gas fired furnace. I also have a Miller outdoor Central Air Unit. The Central Air Unit is wired into the furnace itself with a rocker switch to choose between Heat, Ctr (Whatever that is), and Cool. It also has another rocker switch for turning the fan On or Auto. All of this was done before I bought the place, and I have not messed with anything outside of the thermostat today.

During the winter the furnace would occasionally not turn off and decide to try and cook me. Only way to shut it off was to flip the breaker. This only happened a couple of times and I assumed the thermostat was the culprit. I purchased a new Hunter digital programmable thermostat (44668). I am still doing remodeling (hanging drywall, painting etc...) so I was going to wait till I had the room finished before changing thermostats. Well switching to the central air went rather flawlessly as things warmed up outside. However, a few times in the past couple of weeks I have woke up sweating during the day (Thermostat was set for 72). The quick fix that usually worked was to flip the fan switch on the furnace to On instead of auto and that usually took care of it. When I would flip it back to Auto after a while it would work normally. Sometimes adjusting the thermostat slightly and then back would also work.

Today the same thing happened, however; when I turned the fan switch to On, the fan worked fine, BUT the AC unit did not turn on. I tried flipping breakers off and then back on after a few minutes to reset everything, but nothing changed. Fan worked fine, but AC unit wasn't turning on. My first thought at this point was the AC had died. I figured before calling a service tech I would go ahead and change the thermostat to see if that fixed everything.

First I ran into a wire issue. There were only two wires for the old thermostat (Red and White). I read the manual and did some google searching and wired it up as a Heat only unit since everything else is controlled from the panel on the furnace. (This was also the only wiring schematic for two wires.) I put the batteries in, set the unit up, and then turned the breakers back on. Everything kicked on and appeared to be working properly. AC was running, fan was running, I was happy.

Here is where my current problem arises. Neither unit will shut off now. I have set the thermostat to off, raised the temperature, and nothing shuts them off. Only way to shut them off is to flip both the breaker for the AC and for the furnace. I did some more google searching and decided to try flipping the wires to see if that fixed the problem since I thought they may have been backwards and everything I read said it wouldn't cause any harm to the unit if they were backwards. Turned the breakers back on and same effect.

So now I am at a loss. I do not know much about HVAC and have skimmed through all the topics on here and can't find an answer to my problem. Staying cool is not a problem at the moment, however I have to flip breakers to turn my furnace and AC on and off now. I am wondering what the problem is, and if I can fix it myself. I would rather not call a technician unless I have no other option.

P.S. Sorry if this is in the wrong forum.

~If it isn't One thing, it's Everything Else~
 
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Old 06-19-11, 04:08 PM
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What happens if you undo the wires at the stat?

FYI, I have not serviced this set up, so not really up and up with this rocker... Also, Sure it's Intertherm? I've seen only Coleman having this.. I used to have an Intertherm, and it used the 5 wires t-stat.
 
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Old 06-19-11, 04:38 PM
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your system has a control box, which requires a heat only stat typically only a manual stat will work. Basically the control box will switch from Heat (requires seeing the thermostat circuit closed) to cool (thermostat circuit open) to run. Use a heat only stat.
 
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Old 06-20-11, 08:02 AM
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@ Jay11J

Says Interthem on the panel on the furnace. Haven't Tried completely disconnecting them yet but will try that before I go and get a different tstat.

@ hvactechfw

I figured from the setup that it operated that way. Didn't think that a digital would cause a problem though. I will try disconnecting the wires entirely which should make it not work at all, correct? Then I will head to menards in a bit and get a heat only manual tstat and try that. Also since I have tried a variety of wiring the tstat up is there a way to test to see which wire is for sure which since I have read that color codes (red and white) for the wires are not always followed? Also what is a decent cheap manual tstat to test this with in case that isn't the problem?

Thank you both for the replies.
 
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Old 06-20-11, 09:52 AM
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Home Depot has a good basic manual stat that is not "stealing" power from the system.. It uses battery for this.

When you undo the wire, if all stops, then set to cool, or heat, and touch the two wires then it should run.

if the system run with the wire removed from the stat, then it may be something else going on.
 
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Old 06-21-11, 04:11 PM
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Good news, and also a reference for anyone who may encounter this in the future. After thinking about what hvactechfw said about how the system works I decided to try setting the thermostat to heat. Then I cranked the temperature up above what it was in the house. Since the controller on the unit itself is set to cool the system shut off. Even though the thermostat is wired for HEAT ONLY it only acts as such if it is set to heat. Even setting the thermostat to off still leaves the unit engaged for whatever reason. I am still going to replace the tstat with a heat only version to avoid any future issues, and I saw at menards they have basic honeywell heat only tstats for around $25.
 
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