Forced Air Thermostat help!

[bluestem]

So I have been running our Central Boiler for 3 years now, no problems with anything of concern, just the minor adjustments after initial setup. Fast forward to this morning, wake up a little late, hmmm should be nice and toasty in the house by now, that's odd. Go down and check the thermostat and it still says it's 58, the furnace fan should be running. I have the 2 furnace thermostats setup exactly how the diagram from CB shows only we don't have AC. So my initial reaction is that i blew a breaker, check that, everything is good. So I flip the normal furnace to on and viola the burners kick on and we have heat again, blowers and fan works, getting hot air out of the registers like normal. Turn the propane off again and turn the other thermostat on that just kicks on the fan and nothing.

So after cracking both thermostats open to check the wiring and actually swapping out the thermostats so the one that was fan only is now running the actual furnace and the one that was running the actual furnace is now just running the fan, I get the same issue.

I'm stumped guys, why would the fan come on with the propane furnace but not come on when it's just the fan turning on!

 

[54stude]

Are they electronic programmable thermostats? If so, I think there is a little relay that can fail in there. Also, check the batteries...

 

[bluestem]

Are they electronic programmable thermostats? If so, I think there is a little relay that can fail in there. Also, check the batteries...

I did forget to mention that they both had low batteries this morning so they all get replaced. They are the electronic variety. I was wondering if they little relays might have gone. I guess my question now is, since I swapped them out would the relay be bad in both of them? Seems odd.

 

[mhyme71]

Thermosat problem

Does your thermostat give you the option to just turn on the fan. If so switch the fan on on the thermostat that is wired to the gas heat. That wire should go to a different relay on your control board on the furnace then the heat command wire. If the fan doesnt come on when you switch on the fan then you need to check the connection at the furnace.

 

[bluestem]

Thanks for the help guys, pretty sure I have it nailed down to the fan relay on the controller board on the furnace. Have someone coming to check it out Wednesday. Looks like I will have to burn up a few more gallons of propane this week, sucks! Should be a quick fix.