CMF 80 PG DI Propane wont sense flame

ThermalJake

I am the HO, have been trained by Nordyne (20 years ago), have swapped out atmospheric burner for this power burner about 15 years ago. I have been maintaining, cleaning, etc since about 1999. This trailer is behind my house and contains my mother-in-law...!

Anyway, over the past few years, I have had several problems with igniters that cracked or otherwise could not sense flame. On some occasions, I have swapped it out with a new one, and all was good. On other occasions, I tipped it into the flame a little further, and that did it. I always keep a couple of extras on the shelf, along with an extra control and some other odds and ends. At the beginning of this heating season, the symptoms were present at startup. (4 sec of flame then off, cycle three times, then lockout.) So I changed the igniter, but no good. Then I bent it into the flame and - voila! Off and running.

Two days ago, she called to say she heard a "big boom," and no heat so I went to investigate. Same symptoms. When I went to take the igniter out, it had broken off completely at the porcelain. So I changed it out. These were Supco SSN2200, I think. Basically a low-cost, universal igniter. The next one sizzled and burnt up on the first firing. The next one cracked, and the next one sizzled also. I have one of those left. But I decided to go to the supply house and get a higher quality one (just in case.)

So I bought two... this were also Supco, but the better ones (SIG101) which has the element that wraps around the core. Anyway, the first one was cracked, so I put the second one in. And finally, that one is working, but still isn't sensing the flame (cycles on 4 seconds, three times, and locks out.)

(This might be a good time to buy stock in Supco!)

So, I examined the flame, but it doesn't really look like any of the pictures I see, so I cannot say if it "looks good" or not. I suspect it could be something with too much or too little draft, etc. Or it could be an intermittent issue with the control. Or it could be... something else. I'm afraid that the continuum of bad igniters may be a "red herring." Or that they might mean something, that only a trained tech would know.

I know that this cannot be diagnosed through the internet. And I know that there is no substitute for having a good, qualified tech check it out. But of course, I would only want one that hangs out here, not one from the phone book... heh. (I'm in New Windsor, NY.) But, maybe one of you has some tips, advice, or questions that might lead to such. If any of that is possible, I would welcome it.

Thanks in advance,

Jake

EBEBRATT-Ed

I would suspect a cracked heat exchanger. Air from the fan crossing over into the burner compartment can screw things up. or a draft/flue issue.

Be careful about any possible C0 issues

ThermalJake

I found a local guy who works at a trailer park, and he pushed the plate at the end of the blast tube away a little bit. That fixed it for the end of the season.

However, the problem is now back. I am very busy with work and other old/sick relatives, so I called a local heating contractor who sent several techs out at different times, all of whom basically started with something like "You know it is a 34 year old furnace and an 88 year old mother-in-law...?"

Yes, I know that. But the tendency to give up diagnostics for the "newest" furnace isn't in everyone's price range or their mindset.

The first guy changed out the igniter with a shorter one, thinking it was dipping into the flame too much. The second guy set the fan on perpetually thinking that the firebox was getting too hot (after changing the igniter). The third guy said he wasn't getting enough voltage out of the S89C control module, but when I handed him a spare one to try, it still didn't work.

The first guy sent a scope up the flue and it came back okay (what they could see.) He also checked with a CO meter, and all good. The third guy suggested that maybe the circulator was pushing INTO the firebox and that is why maybe there is no CO in the trailer, and maybe why the flame is curling around the igniter and sometimes melting the wiring.

Of course, the office is now pushing me to "just replace it..." And I might do that, if it is actually required. But I don't want to spend $4K on a new one if I can get away with a $100 blast tube. But I have to somehow convince the contractor to continue diagnosing, and not give up.

What do you guys think?

ThermalJake

ThermalJake

Update tonight. It will respond to a call for heat, cycle through three times of igniting and not sensing the flame, then lockout. Tomorrow I will try to bend the igniter into the flame a little bit and see if I can get it to sense the flame.