Need Help With Gas Furnace Problem

[EagerBeaver]

I am hoping that one of the HVAC gurus on the board can help me. I am having problems with my gas furnace. It is controlled by a digital Honeywell thermostat, which is fairly new. When I set the temperature to 72 degrees Fahrenheit and the condo air temp is 64, the furnace goes on, but only blows hot air for 2 minutes and the temperature does not go to 72. In fact I woke up this morning and the temperature was 59 degrees (!!!) while the thermostat was set to 72. The furnace goes on and then off also when I throw the circuit breaker. When I throw the circuit breaker off and then back on, it goes on, but only blows hot air for 2 minutes and then shuts off. This furnace behavior is not warming the condo adequately in this cold.

I had the furnace tested on October 31 and there was no problem with it then. But now the weather has gotten colder and something is wrong.

I have an appointment with an HVAC specialist this afternoon but wonder if they will be able to solve the issue. I am thinking something is wrong with the thermostat. What do you guys think?

 

[rumpleforeskiin]

Anything is possible, but the first thing I'd check is the air filter. If it's plugged, you whole system could go haywire. Second suspect, a failed thermostat.

 

[EagerBeaver]

The air filter was changed on 10/31 when the furnace was inspected and burn tested, and the filters do not plug in 6 weeks. I think the problem is the thermostat wiring, but outwardly it appears functional. And it is a new Honeywell for which I paid $75 at the end of last winter when the original thermostat failed.

The HVAC company I used also replaced the pressure switch on 10/31 and the furnace was given an approval at that time. My condo complex mandates annual inspections.

 

[Rudolph]

EB, I've had a couple Honeywell's fail on me, they appear to be working but send a faulty signal. Don't get me wrong, one of the best companies to go with but the fact that you bought something decent doesn't out fault. I'm with rumps on this, if your filter is new and not tripping a sensor, then the next most logical is your thermostat.

 

[EagerBeaver]

The HVAC guy just left and he diagnosed and fixed the problem. It was the pressure switch. He was the same guy who came on October 31 and he admitted to me that he did not adjust the pressure switch properly when he was out here on October 31. He told me that the old pressure switch was not adjustable but pre-set to the right pressure. He told me he had thought the pressure switch he installed also was not adjustable, and he therefore did not adjust it. But it was an adjustable pressure switch, and should have been adjusted to 1.2 from what he said. The improper pressure setting was causing the furniture to shut down after blowing for 2 wimpy minutes. He admitted it was his fault, apologized and told me there would be no charge. I thanked him for his candor and wished him a happy holiday.

The hot air is pumping into my living room as I write this and I am headed towards 72 degrees. It is already up to 68 which is warmer than it has been in a while.

 

[rumpleforeskiin]

The hot air is pumping into my living room as I write this and I am headed towards 72 degrees. It is already up to 68 which is warmer than it has been in a while.

72??? You trying to melt the polar icecap?

 

[Rudolph]

Farenheight rumps