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Message
Heater turning on when desired temp is set lower than current temp
Posted on 10/18/22 at 10:21 pm
Posted on 10/18/22 at 10:21 pm
Can't seem to type this correctly into Google to get the results I'm looking for.
Moved into this house after last winter so haven't had to run the heater. I have a PRO1 t705 thermostat. A/C works exactly how you would expect. I set it to 72 and the current temp is 74, it turns on until the temp gets to 72 then shuts off no problem.
With the thermostat changed to heat. If the current temp is at 72 and I set it to 74 nothing happens. If I set it to 70 it turns on and just keeps blowing heat forever until I switch the thermostat to off.
Any thoughts?
Moved into this house after last winter so haven't had to run the heater. I have a PRO1 t705 thermostat. A/C works exactly how you would expect. I set it to 72 and the current temp is 74, it turns on until the temp gets to 72 then shuts off no problem.
With the thermostat changed to heat. If the current temp is at 72 and I set it to 74 nothing happens. If I set it to 70 it turns on and just keeps blowing heat forever until I switch the thermostat to off.
Any thoughts?
3
Posted on 10/18/22 at 10:28 pm to Yung_Humma
Check for differences between the heating and cooling 'swing'. Refer to page 12 of this manual for directions to read and change the two swing settings.
That's all I got.
That's all I got.
Posted on 10/18/22 at 10:31 pm to Yung_Humma
Just a guess.... but it sounds like the thermostat is wired wrong. You might be able to google that model thermostat and learn how it is supposed to be wired. It might be a wire is loose or not connected.
It would be interesting to talk with the previous owner to see if they had the same problem.
Maybe Crawdad can help.
It would be interesting to talk with the previous owner to see if they had the same problem.
Maybe Crawdad can help.
Posted on 10/18/22 at 10:35 pm to Yung_Humma
Just to clean up some details:
Is this a gas heat, or heat pump with emergency heat?
Are there different settings on the thermostat, say "heat" "emergency heat"?
Just a guess is that you have the wrong type thermostat.
E.g. you have a heat pump and you have a thermostat made for gas furnaces
Is this a gas heat, or heat pump with emergency heat?
Are there different settings on the thermostat, say "heat" "emergency heat"?
Just a guess is that you have the wrong type thermostat.
E.g. you have a heat pump and you have a thermostat made for gas furnaces
Posted on 10/19/22 at 5:46 am to East Coast Band
It’s a lennox ml180uh and I’m pretty sure this thermostat is the one originally put on the house. I’ll check wiring this morning
Posted on 10/19/22 at 6:14 am to gerald65
quote:
it sounds like the thermostat is wired wrong
Posted on 10/19/22 at 6:15 am to Yung_Humma
quote:
ml180uh
Looks like it's a gas furnace. The thermostat looks like a single stage, so I don't think there's a conflict there. But, I'm not sure.
I'd really do some wiring checks. It's way too common these jackleg AC guys wire things up incorrectly. Often there are unused wires on thermostats, etc.
Posted on 10/19/22 at 8:02 am to Unobtanium
If I'm looking at page 7 of this manual, the wire showing going into RC is actually going into RH on the one installed on the home. I'm guessing that I need to change it from RH to RC?
ETA: I guess this really shouldn't matter since there's a wire connected RH and RC anyway.
ETA: I guess this really shouldn't matter since there's a wire connected RH and RC anyway.
This post was edited on 10/19/22 at 8:12 am
Posted on 10/19/22 at 8:39 am to Yung_Humma
Wiring seems correct. I've got a replacement thermostat on the way. Should get here tomorrow afternoon, and if it doesn't solve anything can just return it.
Posted on 10/19/22 at 8:49 am to Yung_Humma
It sounds like your thermostat is calling properly for cooling but a “bug” is messing up the heating call, but heat does work for you just not properly. This suggest to me thats a thermostat issue and not a control board issue in the furnace.
As others have recommended check wiring, make sure wiring connections are tight, see if your thermostat has a common wire (C) powering the thermostat, and if not replace the batteries in the thermostat. Weak batteries can make thermostats do weird things.
You can also check the thermostat wiring connections on the furnace control board to make sure they are tight.
If by process of elimination none of these doesn’t fix the issue, sounds like you’ll need a new thermostat. The circuit boards do go bad on them from time to time. Do not replace it with a NEST, but rather a Honeywell or Ecobee.
Also I’m working on the assumption you have a split AC with gas furnace.
As others have recommended check wiring, make sure wiring connections are tight, see if your thermostat has a common wire (C) powering the thermostat, and if not replace the batteries in the thermostat. Weak batteries can make thermostats do weird things.
You can also check the thermostat wiring connections on the furnace control board to make sure they are tight.
If by process of elimination none of these doesn’t fix the issue, sounds like you’ll need a new thermostat. The circuit boards do go bad on them from time to time. Do not replace it with a NEST, but rather a Honeywell or Ecobee.
Also I’m working on the assumption you have a split AC with gas furnace.
Posted on 10/19/22 at 8:53 am to Yung_Humma
quote:
ETA: I guess this really shouldn't matter since there's a wire connected RH and RC anyway.
That’s correct. Red is your 24V power wire with a jumper between R or RC and RH on the thermostat when you have a HVAC split system that cools and heats - not all areas of the country combine both heat and cooling in a split system.
ETA: Good HVAC tech video on potential thermostat problems. LINK
This post was edited on 10/19/22 at 10:03 am
Posted on 10/21/22 at 8:11 am to CrawDude
Thanks for the help everyone. Replaced the thermostat with a new one and everything works now
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