Furnace burner misfiring

[Bain]

I've never seen this kind of malfunction before. The furnace's second and third burners fired, but the first burner didn't. The furnace was located within a laundry closet, and was coated inside and out with lint and dust, etc., so I imagine the jets are merely clogged. Does anyone know of any other explanation for this malfunction?

John

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[hausdok]

Hi,

You've probably hit upon it, but it shoulnd't be in the same room as a laundry anyway, especially if a clothes dryer is located within the same room.

First, it needs 50 cubic feet of makeup air for every 1,000 BTU's and unless there is a fresh air source into the room it's starving for oxygen. Second, if a clothes dryer is in the same room, every time the dryer comes on it will depressurize the area around itself and affect how that furnace fires.

There shouldn't be any air return grills, blowers or other air-gobbling gizmo's within 10ft. of that furnace.

ONE TEAM - ONE FIGHT!!!

Mike

[Bain]

The laundry closet had louvered doors, coated with dust that reduced the free area to who knows what, but the doors were open prior to and during the furnace firing.

[Chad Fabry]

I'm having a hard time believing that the one section is plugged. Positive gas pressure and all that. What worries me is it may not be lighting due to inadequate combustion air and it's spewing NG up the chimney.

I'm not sure what would cause that, but it would bother me enough to recommend that the furnace not be used until it was rectified.

[Terence McCann]

That's a very dangerous condition! If the 1st burner still has gas flowing but the pilot ignition passage has been blocked by lint it is only a matter of time for the right conditions to come along and a major delayed ignition condition to occur. These can be very explosive! This furnace appears to have an induced draft system by the looks of the closed heat exchanger which, would assist in pulling the raw gas up and out, but I wouldn't roll the dice here.

I would advise the owner to the home to call a licensed HVAC company immediately to repair this condition.

The next step is to rectify the problems that Mike and Chad have pointed out.

[kurt]

Yikes! I'm w/Chad; blockage unlikely, but who cares @ this point? Shut it down, start over.

[Bain]

Thanks for the good advice, fellas. I actually showed the seller what was going on and told her to call an HVAC person ASAP. I also phoned both realtors just to make certain my rear-end was appropriately covered.

John

[Gordon]

That furnace hasn't been serviced for quite some time. And around here, many utility rooms have the water heater, furnace, washer & dryer all in the same room. Not only is lint build up a big problem, but as Mike said, you need to have the make-up air. You said the door was louvred, so that would cover the make up air. But that doesn't cover the lint build up problem. And seeing that this hasn't been serviced in a while, that chamber probably can't get rid of the flu products created, because the chamber is blocked , which means not enough oxygen to keep the flame alive. It may fire initially & go out quickly, or not at all. And with the gas still emitting from that burner, there's a possibility of roll out-the gas escaping that chamber, and igniting off the other burners. That unit needs to be shut down immediately, and an HVAC contractor called for service.

By the way-if the furnace looks like this, you can pretty well make the assumption that ac has never been serviced either.

[Jim Katen]

Originally posted by Bain

I've never seen this kind of malfunction before. The furnace's second and third burners fired, but the first burner didn't. The furnace was located within a laundry closet, and was coated inside and out with lint and dust, etc., so I imagine the jets are merely clogged. Does anyone know of any other explanation for this malfunction?

John

One minor observation: it's the last burner that isn't firing, not the first. The gas is fed from right to left.

The burner doesn't have to be completely clogged. If debris is diverting the gas stream out one of the air intake openings, that would be enough to prevent it from igniting. . . for a while anyway. Any halfway competent spider could achieve this.

I share Terry's concern about delayed ignition. Though a nice hot fireball might be just the thing to clean out that burner compartment and restore it to good working order.

- Jim Katen, Oregon

[scott s]

Imagine what the inside of the dryer vent looks like!

[Bain]

That's one of the downsides to our jobs; we can't always find out what the diagnosis and repair were. The listing agent is an old fussbudget, and the seller--due to water damage in the crawlspace caused by adverse grade conditions--now hates my guts because the buyer walked. I don't think the fussbudget or the seller would be receptive to my calling and saying, " Uh, by the way, what did the HVAC person have to say about that misfiring furnace?"

John

[Darren]

John,

Even if he 'hates your guts', I would ask him that question when he calls you up to schedule HIS home inspection. I bet he does....

Darren

[MechAcc]

What manufacturer and model number is this furnace?

Lint will block the passages in the burner light over bar and prevent lighting. It will also cause high carbon monoxide levels in the flue.

Have not seen a standing pilot system on an inshot burner system. Since this furnace does not have a draft hood there is no place for the pilot burner combustion byproducts to go but inside the furnace compartment, as evidnced by the streaking on the left and right of the cover that has been installed above the pilot burner. Then on call for heat these byproducts will be pulled into the heat exchanger by the inducer. This furnace may have been improperly modified from an intermittent pilot ignition system. Call the authorized local dealer and find out.