[Master Brian]

As the title says, I walked in the door, wife at dining table doing homework with kids and she suddenly asks, what's burning..... I thought maybe just a little smell from portable heater that was running, but then it got way worse. I noticed display on thermostat, so I went to check furnace and shut it off with switch. Then called fire department, which came out and checked. All breakers were good. I had pulled display for thermostat off wall to see why it was dark, they asked me to turn furnace back on, so I put display back on wall, it came on, I kicked thermostat up to 75, was set at 69 and furnace kicked in.

The final thought was fan would kick off, so would thermostat, but flame would stay running and was therefore overheating the furnace.

Any ideas? I've been trying to clean the furnace and look for the obvious, but I'm no tech. I can however spot bad wires, a burnt spot on board, etc and I've pulled and cleaned the squirrel cage before, so I can handle the basics, it's testing I can't do. I plan on calling someone tomorrow, but looking for anything between now and then.

The furnace is a Goodman Model GMP 100-3 and was apparently installed in the mid 90's. The thermostat is a honeywell VisionPro IAQ that I installed in the last 7years or so. All wiring is also new since I bought the house in 2008 as I had that all replaced and no breakers were tripping.

A friend texted me an article about fan not staying on, so I'll read that. I also just googled the Thermostat blank screen and came across a post of mine from 5years ago, seems furnace overheat issue will cause that, but I'll re-read that. Here it is if anyone else wants to read as well....

For now, if anyone has suggestions or ideas, that would be great as it is cold out, I luckily have a hardwired electric baseboard and some very nice electric heaters, so i'll try to keep house warm with those for now. Doubt I get much sleep....

 

[Master Brian]

If after cleaning and replacing filters, I can get it to come back on and the fan stays on, should I trust that or wait for a tech to come look?

 

[Master Brian]

For what it's worth, I tried turning just the fan on and it wouldn't come on. The thermostat did come back to life when I flipped power back on again at the furnace, but after a couple of minutes it went dark again. Apparently something is definitely over heating and causing the low voltage to trip.

 

[beenthere]

First, GMP's are know for cracking their heat exchangers, and or popping their crimp rings. Most likely your has already popped it's crimp rings. Remove blower. Use a mirror, and see if you see any rings laying on plate under heat exchanger. If not, then inspect heat exchanger for cracks.

You most likely need a new furnace due to the problem that line of furnaces had.

 

[Master Brian]

First, GMP's are know for cracking their heat exchangers, and or popping their crimp rings. Most likely your has already popped it's crimp rings. Remove blower. Use a mirror, and see if you see any rings laying on plate under heat exchanger. If not, then inspect heat exchanger for cracks.

You most likely need a new furnace due to the problem that line of furnaces had.

I'll google about the cracks on the heat exchanger. Anything in particular I should look for? A friend said take off the exhaust fan, shine light into ports on heat exchanger to see if any light comes through. Obviously not 100% positive test, but a start.

I really think the fan went out and is overheating and tripping everything, as when I let everything sit for some time the thermostat comes back on. Then when I turn it back on I hear a loud hum coming from the squirrel cage area and eventually it trips whatever controls the low voltage(i.e. limit switch?)

Next question is, any idea about equipment breakdown coverage??? I have that on my insurance, wonder if it's worth filing a claim on it....

 

[jimn]

Not sure about breakdown insurance. Not even sure what it is. Usually extended warranties only pay for repairs? If it can't be repaired or is not feasible to repair then customarily the only pay the depreciated value of the device. Which in this case would not be much. You might want to look at what you are paying for breakdown coverage . Most often these coverages cost you a lot more than they will ever payback.

 

[Master Brian]

Well, I called another HVAC person and he came out about 45min ago, determined motor definitely bad, so he pulled it, looked over the entire unit and seemed to think no issue with the Heat Exchanger, just the fan motor, so he's replacing that and going to give the entire unit a thorough cleaning.

His recommendation was that, being an older unit, it was one of the better built ones and he'd just fix this and go from there! So I'm going with that and he just got back with new motor and is installing as we speak.

 

[Master Brian]

Not sure about breakdown insurance. Not even sure what it is. Usually extended warranties only pay for repairs? If it can't be repaired or is not feasible to repair then customarily the only pay the depreciated value of the device. Which in this case would not be much. You might want to look at what you are paying for breakdown coverage . Most often these coverages cost you a lot more than they will ever payback.

The equipment breakdown covers the 'systems' of the home. My understanding is anywhere from TV, to the fridge to the HVAC. The key component is that it has to be breakage, not wear and tear. So a copper lineset to the condenser wouldn't be covered if it developed a slow leak, but if the compressor goes out prematurely it is. I actually had that happen and it was covered. Even though the unit was under warranty, the insurance paid for a complete new unit as it would have been a few weeks to get replacement part and we were experiencing a long spell of 100+ degree days, so they covered that. What I'm not sure about is if the heat exchanger had gone bad if they would have covered that. My guess is the blower motor freezing up, they would cover, but not enough to meet the deductible. I guess I'll have to make a call to clarify. Cost is about $2 per month and in my opinion well worth it for situations similar to this, even if I didn't need it this time....

BTW....thanks for the replies, it'll be nice if the unit gets going soon!!

 

[beenthere]

Well, I called another HVAC person and he came out about 45min ago, determined motor definitely bad, so he pulled it, looked over the entire unit and seemed to think no issue with the Heat Exchanger, just the fan motor, so he's replacing that and going to give the entire unit a thorough cleaning.

His recommendation was that, being an older unit, it was one of the better built ones and he'd just fix this and go from there! So I'm going with that and he just got back with new motor and is installing as we speak.

Have him pull the blower and look on top of the plate the blower slides off of for rings laying there. A flash light won't show popped crimp rings.


The GMP is NOT one of the better built ones.

 

[Master Brian]

I can't confirm 100% that he checked for popped rings on top of that plate, but he did pull the blower and stick his head into the space the blower goes as if he was checking thoroughly. He then looked everything else over very well from what I could tell.

 

[Master Brian]

I will also say he had every opportunity to recommend a new unit as I told him I thought insurance might cover it and he still suggested just replacing blower as everything else looked good.

 

[beenthere]

Do the flames change when the blower comes on.

 

[Master Brian]

I'll look and see. I did ask how to tell if heat exchanger bad and he tried to explain and he also sat there watching it for few minutes when it kicked on and seemed to be watching the flames.

 

[Master Brian]

Do the flames change when the blower comes on.

Ok, I haven't had to chance to look at when the flames when the blower comes on, but I watched that video and I was able to look at the flames once it's been on for a while and I don't see any noticeable rollout, I think he mentioned that. The flames look pretty constant across all the tubes.

I'll look more later when I have a bit more time and reply. I really appreciate the help!

 

[Master Brian]

Ok, I haven't had to chance to look at when the flames when the blower comes on, but I watched that video and I was able to look at the flames once it's been on for a while and I don't see any noticeable rollout, I think he mentioned that. The flames look pretty constant across all the tubes.

I'll look more later when I have a bit more time and reply. I really appreciate the help!

I realized I forgot to reply to this, but I did get a chance to watch as the flames as the fan kicks in and everything remains constant and after watching the video and looking at it in person, I realized that's what the service tech said he was looking for.

Thanks for all of the help, hopefully I get many more years out of this furnace!!! If nothing else, I will start keeping an eye out for the rollout, since it apparently is a common issue and being as this is an older unit!