Furnace runs too hot

[Mosey]

Our furnace has never really worked right. We moved here 5 years ago and it was less than 2 years old at the time. One of the selling points of the house was the "new furnace". Unfortunately, it's not a very good quality furnace, not a brand name that I've ever heard of - Goodman.

I had trouble with it the first couple of winters we lived here, but just put up with it, but last year I had someone come out and look at it. They said it was the type that could run on either natural gas or propane and that the installers had it set up for natural gas - which was a problem because I have propane. He was amazed it worked at all and replaced some orfice (sp?) and made some adjustments.

Well, ever since then it's done a good job of heating, but it seems like it's too hot now. The register that's closest to it gets so hot that I can't hold my hand on it for more that a couple seconds. It runs for a while, then the burner kicks off for a few minutes while the blower keeps running, then the burner lights up again for a few more minutes, then the burner kicks off again for a few minutes while the blower keeps running, then the blower kicks off.

I'm worried that it's running too hot. What do you some of you think?

[RobS]

I can't help you with the specific problem Danny, but we had some problems with our propane range when we moved in so I called the propane company. Their tech was very knowledgable and fixed a couple of things that the installer had missed. You might give your propane company a call to see if they can help [img]/forums/images/icons/smile.gif[/img]

[pbenven]

Is there a relatively equal amount of air coming out of all of the ducts? Maybe some ducts are blocked? There are little dampers on mine enabling to bypass certain rooms.

How's the filter? If it's clogged or maybe the wrong type, you won't be getting enough intake. Anything blocking the intake registers?

First thing is to ascertain that it can inhale and exhale properly.

[DocHeb]

I agree, sounds like starved for return air - limited air flow across heat exchanger allows heat to build up - exchanger reaches upper temp limit and shuts off fuel - exchanger cools down allowing thermostat's call for heat to be answered again. There is a thermostat that calls the blower when the heat exchanger reaches a certain temperature. Another thermostat shuts the fuel off it the exchanger temp is too high. If the "blower on" temperature is too high, there isn't enough time for the blower's air to cool off the exchanger before the upper limit is reached. Possibly the "blower on" thermostat needs to be set lower.

Again, check air filter and make sure all dampers for any return air ducts are open.

Do you have A/C? If the furnace was run without an air filter for some time the A/C condenser coils can become filled with dust and limit air flow.

Some furnaces have a low CFM for A/C and a high CFM for heat. Is your blower working at speed? - early blower motor failure may give low RPMs on the fan decreasing air flow across the exchanger.

Beyond that you probably need to get another specialists opinion. It sounds like your heat exchanger is really getting a high temp workout and that could lead to failure, and we spell that CO (carbon monoxide).

[ScottAR]

Actually, Goodman is a decent brand. They bought janitrol awhile back. I believe they also have some other brands as well. I'm betting on one of the limit switches that have been mentioned or not enough return airflow. Either way, get a HVAC person out there to check it out.

[BrianP]

It could be a bunch of things. Cold air return is one, but air balance could be another (the thermostat heats up before the house does because too much air comes out of the register near it).
I had a tricky problem like yours in my old house - namely the furnace would 'short cycle' over and over again. It was a high efficiency model and the hose which drained water away from the combustion things got plugged because a bug crawled inside and died. The presence of water in the system cause it to shut off. After a few seconds, enough would drain away, or the protection system would reset, and it would start up again.
Unfortunately, I discovered the bug after I removed the hose and blew/sucked on it until the the bug dislodged (into my mouth, natch) [img]/forums/images/icons/tongue.gif[/img]
But one I 'debugged' the hose, it worked like a charm.

[GaryM]

What, you don't have compressed air?

I have to blow out the drain line from my AC system at least twice a month during the season.

[BrianP]

Well, I guess if I would have thought about it, sucking and blowing on a furnace part wasn't the brightest thing I've done in a long time. Besides, 2 years later & I still can tast that bug....