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Thermostat ct87b My heat system shortcycles and never reaches the set temp.

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Re: thermostat ct87b

Your thermostat could be shutting off too soon. What you have to do is take the cover off of the thermostat and look at the bottom right side of the unit. There will be a Zinc plate with little dashs and numbers on it. on top of the plate is a copper triangle, that is what turns the heat off at a certain temp. The triangle is probably out of place and is cycling the heat off before it reaches your set temp. Just carefully adjust the triangle tward the lower left side of the triangle (alittle but at a time) and hopefully that will fix your problem.

Posted on Jan 23, 2008

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Have installed a new Honeywell thermostat. The fan does not turn off even when the room has reached the desired temperature. I originally replaced th ethermostat because the old one the fan ran forever and...

Most T-Stats have a On / Auto on a forced air system. On means the fan will run all the time even if it is not calling for heat. Auto only runs when calling for heat. Does the fan turn off in the auto mode at all? To test it...BE SURE THE FAN IS IN THE AUTO MODE ON THE T-STAT... Turn the thermostat all the way down and keep it there for appox 15 mins. If it is wired properly and the fan limit is set properly the fan should turn off. If it doesn't it is not the thermostat were the problem lies.

Most forced air units have a fan / high limit switch. There is a setting on the switch for the fan to turn on and a setting for the fan to turn off or it has a setting and a differental switch for it to turn off/on. Example - the fan comes on when the temp in the heat exchanger reaches 110 degrees F and will shut down at 95 degrees F after the thermostat is satified...this would hav a differental of 15 degrees F. It may be set to low and the fan continues to run long after all of the heat has been removed from the heat exchanger. This in turn will cause cool air to be coming out of the registers.

Mar 09, 2011 | Honeywell CT87B ROUND HEATING&COOLING...

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My honeywell Thermostat reaches the heating temp. but the fan will not stop running.And yes the fan is set to auto.It just keeps running and running and running.It stays the same temp but will not shut off...

I want to give a simple explanation before I go any further. On the heating side of a unit even though tthe temp has satisfied the thermostat, the fan will run until it cools down the plenum where the air flows from the air handler. There is a bimetal switch called a fan limit that operates the blower when the plenum reaches the temp set on the fan limit switch. Now if your fan keeps running even after the plenum chamber has cooled down, then you could have a fan limit switch that is stuck in the run position and must be replaced in order to correct the problem.

Dec 07, 2010 | Honeywell CT87B ROUND HEATING&COOLING...

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Heat and air do not shut off at set temps changed thermostats same results

How far off is the temperature when it shuts off, and when it turns back on, from what you want?

Are there any drafts coming through the wall where the stat is mounted?

Dec 18, 2009 | Honeywell CT87B ROUND HEATING&COOLING...

1 Answer

I have to play with thermostat to get my heating system on

You did not make it clear if the thermostat is a programmable unit or not. I am wondering if the thermostat is not set on the correct heat anticipation setting. A heat anticipater is a small heater that helps the thermostat turn off before it over shoots the desired temperature setting. If the thermostat is set for a 5 degree setting, it will turn off at 63 degrees if set at 68. If the anticipater was set at 1 or 2 degrees, it will shut off the heater at 66 or 67. Newer thermostats will only allow the thermostat to cycle 6 times per hour so if you never reach the desired temp, you have to wait 10 minutes before it will allow a call for heat. Check the installation instructions to see if there is a setting where you can get the anticipator temperature closer to your set temp. Good luck.

Dec 11, 2009 | Goodman Heaters

1 Answer

How do you stop a shortcycle

Go into your program and set the differential. Factory default is 1 degree set to 2. Rus

Nov 28, 2009 | Honeywell Electronic Programmable...

1 Answer

How to use a round circular honeywell thermostat? I turned round casing to mark heat , no heat on??

If you turned the ring and the pointer moved, then you are using the thermostat correctly. Turn the thermostat up above room temperature (the temp on the bottom of the thermostat) Make sure all your switches are on, and that the fuse or circuit breaker is also on. If you still do not have heat after verifing all these things, then it is most likely a problem with the heating appliance.
Also, if it is a heating and cooling thermostat, make sure your lever is in the heating mode. Hope this helps

Sep 17, 2009 | Honeywell CT87B ROUND HEATING&COOLING...

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Gas heater shuts off & won't come back on

sounds like the thermostat replaceing it should help you could try cleaning the old one they can get dust it them

Feb 25, 2009 | Honeywell CT87B ROUND HEATING&COOLING...

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look at the old thermostat and in the middle of it theres a arrow that is pointing at numbers that is called a heat anticipator. then on the new thermostat make sure that its set the same.

Feb 21, 2009 | Honeywell CT87B ROUND HEATING&COOLING...

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Hot air does not come on

common color code is as follows:
Terminal Wire Color
W White
G Green
Y Yellow or Blue

This does not guarantee your thermostat was wired to common color code. Assuming it is a single transformer forced air heating and cooling system the following is likely your problem there should be a RC & a RH termial on your new thermostat incase you need a split sub-base for multiple transformers. My guess is that you are connected to RC, if there is not a wire to RH the heat function will not work. the thermostat should have been supplied with a jumper to connect RC & RH together for single transformer applications. If not any small gage piece of wire will work, if I have assumed incorrectly please give me more info about your system.

Dec 11, 2008 | Honeywell CT87B ROUND HEATING&COOLING...

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