Cleaning Burners

salter07

My Lennox G26 will run as it should for about 2 1/2 minutes and then shut off. I'm assuming it is a cleaning issue as, when I cleaned out my electronic air filter, it was filthy. Also, the vents smell like something's burning. My plan is to clean out the burn chamber next and I think it looks fairly straight forward.
Two questions: Does my assumption seem reasonable?
Do sporadic orange flames (as opposed to constant blue) indicate debri in the burners?
Thanks in advance

yuri

Incorrect. If the filter was dirty then the burner was short cycling on the high temp limit control below them and it is now weak and inaccurate. A bit of orange is not an issue. White flame is a big problem.

read this post and do a temp rise test and buy a new limit control from cozyparts.com

The underside of your AC coil may be dirty AND you may need to remove the main blower fan and crawl in the cabinet and clean the dirt from the secondary heat exchanger coil as both are probably slowing down your airflow.

Furnace Cycle Problem

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joecaption

Not a wise choose to try working on anything gas. It's not very expencive to get a cleaning done and far less likly to go boom and you go bye-bye.

salter07

Thanks YURI,
Looks like you've probably saved me some labor and frustration (I hope). The LED Diagnostics also indicate "primary/secondary limit switch open," which seems to agree with your diagnosis, right? Glad I didn't start taking things apart before asking... I still don't know exactly what the high temp limit controller looks like, but I've started the ordering process through cozyparts/lennox.
One more question:
Should I clean out the combustion chamber anyway to prevent this from happening again in the near future?
Thanks again

yuri

No. combustion chamber has nothing to do with your problem. poor airflow does.

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salter07

So I bought a new High temp limit controller from CozyParts and installed it - easy. However, I still have the same problem - short cycling. The LED still indicates that "primary/secondary limit switch is open." Do I need to reset something or should I remove the the main blower fan and clean the secondary heat exchanger as suggested above.
Thanks

biggles

if your electronic was filthy then check the squirrel cage fins for dirt then if you have AC the inside of the evap coil might be packed....all leading to a hi limit trip shutting down the burner and over heating the heat exchanger..if dirt builds up on that fiter it just moves thru the furnace and collects...dust is burning off the heat exchanger

yuri

clean the secondary heat exchanger coil ASAP as that overheating is going to drastically shorten the life of the main heat exchanger and collector boxes..

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Marty S.

Electronic air cleaners really need cleaned monthly. After they get a little dirt and ash built up it acts as an insulator making the electric cells useless for filtering. Same as not using a filter at all.

yuri

we stopped selling them altogether. give off an ozone smell and less than 5% of the people know how or maintain them properly. a 16x25x5 merv 10 slides in perfectly in those old Honeywells. the rest we rip out and put a HC filter box in.

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salter07

Thanks guys,
I removed the main blower and it looks very clean & dust free. The coil above also seems clean (below the main heat exchanger). What is that called?
What do you think of this theory?
The thin layer of fiberglass insulation (around the wall opening from the electronic filter) is falling apart. It doesn't seem like it would cause such a consistent problem, but could that be the debri that's getting in? Can I remove the insulation off that wall altogether? I think I need to whether I replace it or not. Can you tell I'm looking for the easy answer?
I like the idea of replacing the Honeywell elec. filter. What's that Merv 10 gonna run me?
Thanks again for putting up with the newbie...

yuri

coil above fan is the secondary ht exchanger.

check the underside of the ac coil for dirt etc.

you can remove the insulation but unless you actually see it getting into the fan I would leave it alone. it is there for sound proofing.

filter , depends on where U buy it. $30-40 or more. buy a merv 8 or 10. get your ducts cleaned as the filter will plug quickly and it sounds like they need cleaning anyway. don't go with the cheapest guys as they do a dog and pony show. the more reputable guys have bigger vacuums and spend the time to do it well. measure the size of the cells/eac as some of them were 20x25.

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salter07

OK, this is likely my 2nd to last post on this as I have a pro coming tomorrow. I'll let you know what we find out. One interesting/troubling thing to note is that the PVC inducer exhaust pipe has a pea sized hole in it that someone once covered with silicon caulk. I don't know if that could be related or not. Visually, the AC coil looks clean. I hope it's not a cracked primary heat exchange, but I guess we'll see. Thanks again for all your input.

yuri

......

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