Ignitor Position - Gas Goodman GMP0753

radilly

Looking for help assessing the expected position for an ignitor on a Goodman GMP0753. Let me start with the problem / concern. While I was replacing a solenoid in a humidifier I noticed a decent "pop" when the unit was starting. This is a screen grab from a video I took (since it happens fast).



Doesn't look very safe... I thought it might be a marginal ignitor so I pulled it out to check it, but it looked OK.** I did note that the bracket has a slot which was too narrow to fit a tab on the ceramic - so it's likely a replacement which was "close". On reinstalling it, I noticed that the glowing part was pretty far to the side of where the gas flows, i.e. not very centered.



Since it's New Years day, I thought I'd try shimming the bracket a little to move it toward the center of the gas flow. That seemed to help considerably. Being an amateur I have no sense of what's normal. Actually my instinct is it would be better turned 90 degrees so the gas flows around it easier. From what I've read a Silicon Nitride ignitor is preferable if it can fitted (but the question of position remains).

Any suggestions? - - - Much appreciated.


** Note that https://www.youtube.com/watch?v=FunjhjWk98w points out that you can just check the resistance to avoid pulling the ignitor out. I wasn't sure what is expected, but he states 40 - 90 ohms. He also seems to be a fan of Silicon Nitride.

SuperTech

My suggestion is to be prepared to replace the furnace. Call a pro who can use a digital combustion analyzer. It doesn't matter whether using a nitride or carbide igniter, flames rolling out like that is usually an indication of heat exchanger failure. Please don't operate the furnace until a professional checks it out. I'm concerned about carbon monoxide poisoning.

The position of the carbide igniter in the picture is fine, it would not cause flame rollout in a safe furnace.

JUGHNE

Was the draft inducer fan running?
Was the pressure switch jumped out?

HVACNUT

No problem with the igniter at all. Its exactly where its supposed to be.
Since you captured it, it's not the first time.
TURN OFF THE GAS!!!
Aren't the burners near the top of the cabinet?
Those flames are low down.
Can you post a pic farther back with the door off to show the whole burner compartment?
The rollouts should have open the circuit immediately.
There is a serious problem there. Potentially disastrous.
Shut the system down and turn the gas off off off.
Call now for a gas heating pro to come out tomorrow or ASAP. You'll be paying triple rates today.
Please dont touch anything as the tech must see things as they are.

DZoro

Oh my,,,,, shut off the gas, time for a professional. Don't do anything, if you did any changes please let him know all that has been done.
D

SuperTech

Please let us know if you got this information. I'm seriously concerned about the safety of everyone in the home.

radilly

Thanks folks! Appreciate the quick replies!

SuperTech said:

My suggestion is to be prepared to replace the furnace. . . . usually an indication of heat exchanger failure. Please don't operate the furnace until a professional checks it out. I'm concerned about carbon monoxide poisoning.

I understand these Goodmans or generally good, but the exchangers may fail quicker than on others. Discussed with the tech last season and he suggested it still has / had some life in it. We have a CO detector, but I have requested a call when folks get back to work tomorrow. Seems like often I need professionals on Holidays and weekend! ;-) (It's a bit chilly here not to have working heat.)

JUGHNE said:

Was the draft inducer fan running?
Was the pressure switch jumped out?

Yep - inducer is fine, and the lockout is in place. Replaced it last season - and tested the switch then.

HVACNUT said:

Since you captured it, it's not the first time.

. . . .

Those flames are low down. Can you post a pic farther back?


The rollouts should have open the circuit immediately.

Actually - based on a sound - I suspect it's been doing this for some time. The change was gradual. Had I not worked on the humidifier yesterday I'd likely not have noticed the issue.

The flame in the exterior shot align very closely to the interior picture above - if anything a little lower. The "louver" in the cover might also direct it downward.

If I understand the (typical) rollout - the sensors are often above where the flame is. If the flue is blocked the flame, I thought, would tend to be near and above the openings in the interior shot.

The flame in the image is very short-lived. I stepped through the cell video 1 frame at a time and its all over in about 5 frames.

. . . Not sayin' that's good of course, but it may be why the rollout sensor isn't tripping. (I'm going to go look at that more carefully.)

I appreciate the advice - and it now seems that much more urgent. I do take it very, very seriously. While it certainly should be checked out, I do observe that moving the ignitor slightly toward center seems to have dramatically cut the flame I can see outside the unit - to nothing.

When the tech comes I'll share the little I've done and my observations. (I'm a decent mechanic, but spent much of my career partly doing customer support of software - so I think I get it.)

Thanks again for the prompt responses, the explanations and warnings!

SuperTech

Thank you!😊 It sounds like you have handled it correctly. Just don't put all your faith in the CO detector. Only a proper technician with the right tools can ensure safe operation.
Goodman gets a bad reputation due to poor installation by the DIY/Hack types that buy the equipment online. I don't consider them any better or any worse than other furnace manufacturers. They all have good and bad models and none of them are designed to last very long.

radilly

SuperTech said:

Just don't put all your faith in the CO detector.

Yeah ... just saying to the wife it might be worth picking up a new one. I don't have tools to check mine (I worked for an outfit that made portable, wearable CO and other gas detectors at one time).

I want to add a little more information from another look-see. (Others may refer to this later.)

HVACNUT said:

Can you post a pic farther back with the door off to show the whole burner compartment?

So here's the "business" part of the interior with the front panel alongside for reference. The burners are pretty low relative to the grill. The ignitor is on the right, and there's a solid horizontal plate (green arrow) covering the area well - between the burners and the gas valve - running from the back to close to the grill. The flame seemed to be coming out the lower right corner of the grill in the images above.



This is the full interior, upper half of the furnace. Blue arrow indicates what looks like the rollout sensor. Assuming it's good, I'm not sure why it's not tripping. (Plan to ask the tech.) But, as you likely know, thinking about electrical motor controllers or fuses for motors, there's some curve where the current can spike over the nominal rating, but it has to be sustained for some period of time to trip the protection. Motors draw a lot of current until they get up to speed. Might this be similar?? Definitely saw flames, but 6 video frames at 30 fps is about 0.2 sec in duration.

One last observation. I nudged the thermostat to watch the furnace, with the cover off. With the ignitor tipped slightly closer to the center**, the "rollout" is minimal. BUT, I noticed the furnace cycled - i.e. the ignitor came on, I think I heard the gas valve open, but no ignition so the flame sensor caught that. The inducer fan clicked off for a second, and it retried the cycle - this time igniting. My wife said she thought she noticed that at least one other time this afternoon.

I suppose in the short term, given the choice between an extra cycle to ignite and flames shooting out through the grill ... I'll go with the former for now!

Again - Thanks - I'll post when the tech looks it over...

** I stuck a piece of copper wire under one end of the plate holding the ignitor - you might see the black insulation I left on part of it - and snugged the screws down (unevenly) to moved it left slightly.

radilly

UPDATE: Tech came today and looked the furnace over. Not terribly conclusive, though he went over it in what seemed like a logical way to me. Interestingly (to me) last night I was thinking the filter hadn't been changed in a while, and he also asked about it - so I changed it out. He cleaned the flame sensor and checked the rollout switch, which trip in the course of trying various things. He suggested, based on the age of the furnace, at about 25 years, it might be a better investment not dig too deep into the root problem(s) and just plan on replacing it. After checking it out he thought it would be OK to address it in the Spring.

We also got a new CO detector... just in case!

DZoro

Hmm, he didn't remove, clean, inspect the burners? Perform a combustion safety test?
Should have done at minimum the above.
Understand not putting much into it, but... did you show him the pictures you posted on here?
D

radilly

Indeed. Tech had worked on it before, and definitely understood the issue. I think that's why I was the first stop of the day. Embarrassingly, I think replacing the filter helped somewhat, and I replaced the ignitor (without the shim) which wasn't terribly expensive. Seems to be behaving reasonably well.

HVACNUT

@radilly
When in doubt, replace the air filter.
It's not an ignition problem.
With a plugged air filter, maybe if the blower motor was running at the time of ignition or run, a cracked HX might cause that.
But you posted Godzilla flames and the tech said the rollout opened.
Find a new tech. Nothing got better with an air filter and a shim.
You have a serious issue there so dont die before you can help keep our trade in business.
Pretty please, with sugar on top.

unclejohn

That looks more like delayed ignition then flame roll out.