Gas and Oil Home Heating Furnaces - Nordyne Problem

Model # G5RA072C-16

Everything starts out fine, the flames light up and my flame sensor is fine as I have cleaned that. Once the blower starts up though, the 3rd flame starts to sputter and has minor blowback, tripping the safety and shutting the flames off. It doesn't cycle back through because the little safety has been tripped and I have to go hit the little button on it. It's 56 degrees in my house currently and its not very nice. :)

I have run out of things to do, we are broke so we can't call a repairman yet. Any suggestions?

Ok, someone told me that since I have central air hooked up to it that it would probably be a good idea to get into the top of my furnace and clean it out as it is supposed to be done twice a year. I opened the top and looked down into the furnace with a flashlight and the tubes that the flames go through are rusted and busted open at the first turn. I am going to need to replace the whole furnace aren't I?

Sounds like you have a thoroughly rusted out heat exchanger.

Often heat exchanger are warrentied for twenty years to the original purchaser ---even longer sometimes. If you can get the replacement under warrentee, replacing it may be worthwhile. Otherwise, a new furnace is probably best.

If you do indeed have a bad heat exchanger(which it sounds like you do) it is very unsafe to operate in that condition. I would have disabled it. You will be putting carbon monoxide in your living space, you will get sick and could die. I'am not trying to scare you, just want you to be aware of a very real danger.

As soon as I saw the holes I turned off the circuit breaker. I know about carbon monoxide and it scares me, doubly so with a pregnant wife. I have a guy coming out on Friday to give me an estimate on a new furnace. I don't think I am going to upgrade, I currently have an 80% efficiency. I don't plan on living in the house for much more than four years, so I'll try to stay with 80%.

Let us know what kind of quotes you get:thumbup:

I've gotten 2 different quotes so far and I am waiting on another later today. The two I have so far are for Paitson's Brothers and they do Lennox systems.

For the G40 they quoted me $2006.00 +tax. That is an 80%.

I had heard that there is a $400.00 state rebate for going to a 90%, and my gas company does a $200.00 rebate for going to a 90%. So I had thought that maybe I could get away with a better deal to go with 90%.

Hoosier Heating and Cooling quoted me $3400.00 for a 90%. They aren't going to charge me tax. They are doing Tempstar DLX 90 or T9MPD.

The HH&C guy told me that my cold air return was too small and that it could burn up the furnace if I leave it that way. I don't know if I should believe that or not. He also wants to put in a new thermostat in a different place, above the return. I have no idea if he is telling me straight or if he is just trying to get more money.

Edit - 3rd guy just left and he installs American Standard. I had him quote me on an 80 and a 90. The 80 after tax was 2023.90. That is less than the first guy. The 90 was 2544.90, a lot cheaper than the second guy. This person said the same thing about the return supply so I guess the other guy wasn't trying to sell me anything I didn't need.

I guess that question now is quality. The third quote sounds the best, so I will probably go with them. My frigidair/nordyne is a pretty crappy brand anyway, so just about anything would be an upgrade.

What do you all think?

I'm no installer. But if it were me, and I wondered about what the best buy would be, I would want to know what their warranty covers - and would be most interested in the part about the heat exchangers, and if they cover part AND labor. And I might also see if there are any service bulletins out on any of these brands heat exchangers. That would cause me the most concern. Other stuff is bolt on stuff and can be DIY-ed.

Granted though, with newer units coming out onto the market all the time, I suppose one cannot learn about any service history if there is none. In that case, it is the warranty and a companies reputation, I guess.

Also, with any of these quotes, and by comparing different furnace types, be sure to find out which are "closed combustion", and which are "open combustion" systems. The closed style will not draw cold air into your house to fuel the combustion!

As far as cold air return sizing goes: Have them explain the details of why this is necessary, and see if that makes sense. Post their responses here. Even if you have to call them back up and say, "Why is it again that you....."

The small cold air return is I guess not allowing enough air in making the heat exchanger area too hot, causing my furnace to overheat. One of the guys said that is probably why my current heat exchanger is blown out.

Also, they seem to have the same warranties. The one that was 3400 has annual service checkups for free though, but I dont think that is worth the 1000 extra dollars.

I've been working on a newly acquired duplex with a 50,000/45,000 Btu Goodman furnace, that rapidly limits. It has a L240-30 limit and it was zipping right on up there. I drilled a hole in the furnace just above the limit switch and stuck my 6 inch probe thermometer in there, and the needle buried past 220(high number on my thermometer) in about 2 1/2 minutes!

The cold air return size is 8 -10 inches wide and the length is 24 inches. I found a wrong size typical 16 x 25 x 1 filter crammed there, and I discovered it can only take the more rare 24 inch. So I got suspicious about past tenants leaving out the filter. I removed the blower and found the underside of the secondary caked here and there, in a splotchy pattern, so I cleaned that. I cleaned the blower motor itself, and each blower wheel vane of tons of caked on dust. By doing this I upped the flame shut off/high limit time.

Then today I pulled out the A-coil, and to my surprise, that was quite good. I guess the secondary exchanger fins trapped most the dust first. I still was not satisfied with the run time, even though I improved it.

So then (for now), I swapped the high speed A/C motor wire (high) with the heat wire (med. high). Now I more than doubled the time it takes for it to high limit (now 6 minutes)

But you mentioned you think maybe your cold air return is not big enough. Get this: The cut out for my Goodman A-coil is only 10 x 16 1/2 inches. All the air has to go thru that cut out. But get THIS: The opening for the air to go up through the A-coil is only 7 x 16 1/2. And tack on the fact that those fins are super close together. And couple THAT to the fact the air FIRST had to go thru a finned restriction of the secondary exchanger. So I wonder how they figure that a furnace like this is NOT going to high limit. ???

I am also going to buy a new limit switch, as the one that is in there may have gotten weak from all the limiting. And I have caught it limiting, per my probe thermometer, from 180-200. And I could tell by the temp rise that as the temp gets hotter and hotter, the longer it takes for the thermometer to climb. So I'm hoping that a brand new L240-30 will truly shut off at a hotter temp. And perhaps maybe it will not even get there during normal furnace cycling.

Go with the American Standard but check out the installing company.
Do they have pictures of other installs or other customers that You can call.