I had my 3 year old mid-efficient furnace serviced a few months ago. I have a 4 room small bungalow. The Honeywell thermostat is set to say 72 and it says it reached 72. However, an independant thermometer indicates that the temperature in the room is only 70 and the other 3 rooms are 68. I don't know if this is relevant or normal but when the furnace fan comes on it blows cold air until it warms up. brrrr! It seems to start up about every half hour for 10 minutes. I'm in Toronto Canada and it's going to get colder. \r\n What's the deal with the thermostat and why is the furnace working that way?

Hi, these mechanical thermostats have what is called a heat antcipator on them. If you remove the cover you will see in increments or numbers such as 1.0, o.1, .2, .3, .4 or o.1, 2, 3, 4, . The stat and main gas valve work together and have to draw the same amount of amps to cycle the unit properly. This stat will have a copper arrow pointing at a number. A good place to start is to set it at .4. If the unit does not cycle right, set it at 1.0 and go from there until it cycles. Let it go through several full cycles during each time you adjust it until it is correct. These are good dependable stats as I have many on my service truck. If it doesn't take care of the problem, take it back and return it for one that is not faulty which happens often. Best of luck to you.
Ps, the small manual that comes with a new stat has that information on it, anticipator settings.
Shastalaker7
A/C, & Heating Contractor

No problem, the average temperature swing for thermostats is 2-4 * F.

I had this same problem with my 6300B thermostat. I did not see this when I installed the tstat and did setup for it the first time. If you go to page 16 of the install guide, there are instructions for setting up your tstat for your furnace and AC. The setting I had wrong was on page 20 of the guide. It defaults to a setting for a furnace/ac that is less than 90% efficient. When I changed the setting to a furnace that is more than 90% efficient, the fan not turning on or off problem went away. The setting on page 20 should be set to "3" if you have a more than 90% efficient furnace/ac. Hope this helps your problem

Hi, check page 22 in your manual, it says "Adjust the screws on the back of the thermostat as instructed on page 7." Your furnace is a 80% efficiency but is also a high efficiency 2 stage heating system so try adjusting screws A and B both ways and see which gives you the correct cycling.
Your manual is here:
http://customer.honeywell.com/techlit/pdf/69-0000s/69-0653.pdf

remove batteries let sit a few minutes reinstall.
if still bad replace they are not servicable

The thermostat tell the furnace when to run. It sounds like a thermostat issue since the furnace is producing heat.
Eric

check transformer in furnace... thermostats get there power from it....not the room its in

Sounds like your repair man ripped you off. He should have stood behind his work.
1. I would try to clean the flame sensor located just below the burners. It is connected to "one" wire (Not the two wire) clean rod with sandpaper.
2. The old and thermostat could have a had a bad heat anticipator. if the new t/stat is not digital the heat anticpator on the T/stat needs to be adjusted. slide the small adjuster arm under the cover to about .6 or .7 and see if the solves the problem. if the t/stat is digital it should be preset from the factory.
3. last resort have a service man check your pressure swith. could be a slow inducer motor, blocked or bad vacum line, or a restricted drain or flue pipe.
Good luck!

The Thermostat Wizard is an interactive tool that will guide you through wiring and troubleshooting your thermostat, as well as programming it to the most comfortable settings for you and your family. Simply answer the questions from the Thermostat Wizard to correctly connect, troubleshoot and/or program your Honeywell Thermostat. You can even print the instructions and bring them right to the thermostat to help make things easier.
Go to: http://yourhome.honeywell.com/Consumer/Cultures/en-US/Support/Thermostat+Wizard/

However - the problem is probably not with your thermostat but with your furnace. It is most likely a dirty flame sensor - a maintenance issue. If you have not had your furnace serviced recently (more than 1 year) that is where you should start. Modern furnaces require regular maintenance.


Please rate my answer!

sounds like the flame sensor needs to be replace. You can try cleaning it with steel wool. This will get you by for a little while.