Strange Furnace Issue

[paulsomlo]

I went down into the crawl space recently to do yearly maintenance on my GFA furnace and found both of the access panels for the squirrel cage/motor laying on the ground. The panels are sheet metal with a single flat spring for retention. I'm sure it's back pressure, but in the 25 years I've been in the house, this has never happened before. I did close a bunch of vents in unused bedrooms several heating seasons ago, with no repercussion until now. Also, when the main burner fires up, it does make quite a bang. My question is, what could have changed to blow those access doors off?

 

[PWC Repair]

Age, combined with shutting off flow has caused condensation and rust in the heat exchanger and/or draft inducer. Now, when it lights up, you have a small explosion going on at the furnace.......not to mention carbon monoxide. Time to get it inspectes ASAP and replaced.

 

[paulsomlo]

No draft inducer - it's about 50 years old.

 

[PWC Repair]

Ummm, ya......time to replace it before it kills you.

 

[CoogarXR]

Does it have a pilot or electronic ignition?

 

[paulsomlo]

Pilot

 

[Chilliwack Murray]

Personally I'd replace that sucker but at the very least you need to have the heat exchanger inspected. If the 'bang' you get when it lights is able to pressurize the ventilation system it sounds like it is breached and can just as easily fill the ventilation system with CO. This isn't something to take chances with, at very least get a CO detector in the living area ASAP and google the signs of CO exposure. ASAP as in don't even let anyone in the house at this point with the furnace able to run.

 

[paulsomlo]

Took your advice - I just got back from Home Depot with a CO detector. I ran the furnace and moved the detector between several rooms and get a reading of zero.

 

[TurnipTruck]

I will post this again. Carbon Monoxide detectors will not give instantaneous readings.

 

[fitter30]

Look at the burner with the blower off and the blower on does the flame change? Your thinking 50 year old furnace early 70's can't even be 80% efficient. The heat exchanger was built with baffles in the flue passaways are gone. Even in if the heat exchanger might still be good burners area compromised. No different running a 30 year old ac unit way beyond its life. Do they work not like new neither does anything mechanical. Check with your electric company and state for rebates and or tax breaks.

 

[American Locomotive]

It could just be the "bang" shaking the furnace and rattling the doors off. Investigate the delayed ignition issue - it could be as simple as a dirty burner or a pilot flame that needs adjustment.

 

[paulsomlo]

I will post this again. Carbon Monoxide detectors will not give instantaneous readings.

I've had it in the house now for about 2 hours, still reading zero.

 

[paulsomlo]

It could just be the "bang" shaking the furnace and rattling the doors off. Investigate the delayed ignition issue - it could be as simple as a dirty burner or a pilot flame that needs adjustment.

That's quite plausible.

 

[iflyatiger]

Low level co detectors.. These work great when you want a low level detector and low level alarm. I have used this brand for many years and they really works well.

HOME - CO Experts

 

[PoorUB]

Propane furnace?

Propane can light hard. Often, just pulling the burners and cleaning them will clear up hard ignition.

You might find the burners are shot.

 

[paulsomlo]

Propane furnace?

Propane can light hard. Often, just pulling the burners and cleaning them will clear up hard ignition.

You might find the burners are shot.

Nope, nat gas.

 

[Bert_]

It's called delayed ignition. @PoorUB is right that dust and rust can plug up the burners and cause it.

My furnace had delayed ignition on one of the burners a year or two ago. Wire brushed the channel that transfers the flame from one burner to the next and it works perfect again.

 

[paulsomlo]

It's called delayed ignition. @PoorUB is right that dust and rust can plug up the burners and cause it.

My furnace had delayed ignition on one of the burners a year or two ago. Wire brushed the channel that transfers the flame from one burner to the next and it works perfect again.

Do I need to turn off the pilot to do this? I could shut down the furnace and run the fireplace for a while.

 

[American Locomotive]

Do I need to turn off the pilot to do this? I could shut down the furnace and run the fireplace for a while.

I mean to do it safely, you probably should turn the gas off to the unit. You will have to look at it. Many furnaces are pretty easy to remove the burner assemblies on .

 

[Bert_]

Do I need to turn off the pilot to do this? I could shut down the furnace and run the fireplace for a while.

Just shut it down. You can have it cleaned and back together in 20-30 minutes.

 

[PoorUB]

Propane furnace?

Propane can light hard. Often, just pulling the burners and cleaning them will clear up hard ignition.

You might find the burners are shot.

Nope, nat gas.

Surprised!
But it can happen with natural gas too, but unlikely. I would shut off the power and the gas to he furnace, pull the burners, and clean them. You might even have to replace them if they are rusty. Surface rust is no big deal, but I have seen the burner slots rusted out.

Also, if the burners have little "wings" on them, they are cross lighters. The get dust in them and it is all it takes to cause delayed ignition.

 

[paulsomlo]

Thank you all for your replies - for now, things are stable - my CO meter is still reading zero, and the access doors are intact. At some point, I'll get down there to clean the burners. I really have to be in the right mood to enter the crawl space; immediately upon entry, I have to crawl under four large round ducts, then over two large round ducts. Head height is of course limited, it's a dirt floor - dusty, mice droppings, loose fiberglass insulation; I don't dare go down there without an N95 on. I refer to my crawlspace as "The Devil's A-hole", and nothing makes me regretting buying this house more, than a trip to the crawlspace.

 

[engineer2]

I need to do mine too. If I have aggressive lights, it's usually time to clean the burners and everything else.