Flue Damper keeps flying across the room

MichaelG · February 2018

I have been living in a home I purchased for about a month and on several occasions I have walked into the boiler room to find that the flue damper has come out of its seat in the boiler flue and wound up on the other side of the room. It even happened once and was discovered by an HVAC guy who was replacing a noisy circ pump for me. He found it and shoved it back in, but did nothing else.

This is an oil-fired hot water boiler.

My question is, why does it keep happening? Is it as simple as the clamp it seats in should be tightened?

I suspect the issue could be that it has been damaged and is no longer "flapping" open correctly when there is a burst of high pressure behind it. This is evidenced by some scrape marks made by the damper in the perimeter of its housing (see pictures). There is some horizontal play in the damper and when slid to the right side (as it seems to do), it can't move through its travel freely without hitting the housing. I would think the damper shouldn't be able to touch the housing at all, which has been my experience in previous residences with oil boilers.

Should I replace this? What are the tricks to getting the action set correctly with the weights?

Jamie Hall · February 2018

The only way that can happen is from a delayed lightoff from the burner, causing a mini explosion in the firebox.

May I respectfully note that explosions, mini or not, have no place in your home

There are a number of possible causes for the problem. You should get a qualified oil burner technician in there as soon as you possibly can -- like tomorrow if not sooner -- to clean and adjust the burner and its controls.

MichaelG · February 2018

I can confirm that at times it does seem as though when the boiler fires, there’s something of a pressure wave generated if I’m standing in the room next to it. I wouldn’t use the word “explosion” to describe it, but it’s similar to if you don’t quite get the gas to ignite on your stove for a few extra seconds. I guess this is what you mean by “delayed lightoff”.

Jamie Hall · February 2018

MichaelG said:
I can confirm that at times it does seem as though when the boiler fires, there’s something of a pressure wave generated if I’m standing in the room next to it. I wouldn’t use the word “explosion” to describe it, but it’s similar to if you don’t quite get the gas to ignite on your stove for a few extra seconds. I guess this is what you mean by “delayed lightoff”.

You might say that...

It's not supposed to happen. It's unlikely that it will get better with time. It is quite possible for it to delay long enough eventually, and get enough unburned fuel in there before it fires, that the "pressure wave" will blow the breeching apart. This is undesirable...

Get the burner adjusted properly! Now!

ratio · February 2018

It's certainly not right & has the possibility of becoming quite dangerous. Have it looked at by a competent oil tech as soon as you can. Try the "Find A Contractor" button in blue at the top of the page.

unclejohn · February 2018

Birds and bees fly not so much dampers.

EBEBRATT-Ed · February 2018

@MichaelG You need to do what @Jamie Hall & @ratio said before you have worse problems.

And a few screws in the barometric damper won't hurt.

Picture this,

If you continue to have delayed ignition and your flue pipe comes apart or becomes dislodged from the chimney what do you think the best outcome would be?

It wouldn't be carbon monoxide poisoning or a fire.

Leonard · February 2018

Get it looked at. NOW!

Little background on my 60 year old oil furnace.
Listen as burner starts. When oil pump starts turning fire should start right away. IF fire starts after second or so that's typically delayed ignition. If fire doen't start right away then firebox fills with flammable fuel/air mix similar to a car engine. Then when it finally ignites it goes BOOM, hence the pressure wave that blows your damper across the room. This is not normal operation

Guessing your flammable mix blows long enough to make it's way into flue pipe before igniting with a BOOM. Not good , it might blow it off/open and then it's potentially fire or CO poisoning time.

Sounds like the damper getting blown across the room acted as a pressure relief so flue pipe was not blown apart/off. You've been lucky so far. Get burner looked at NOW. On mine delayed ignition is a cheap fix, and comes from furnace not being maintained regularly. Nothing good comes from letting delayed ignition continue, it only gets worst. (longer delay and bigger BOOM)

New England SteamWorks · February 2018

That's the problem with old houses. You never know if, or whom, haunts them. In your case, I suspect a previous (and now deceased) owner was a frustrated boiler technician, and now he spends his days flinging your damper about.

I suggest appeasement. Buy a second one and leave it on top of the boiler.

EBEBRATT-Ed · February 2018

@Leonard , not all burners fire immediately on starting. Many have delayed oil solenoid valves or prepurge

Solid_Fuel_Man · February 2018

Also note the soot around the strap-on barometric damper (what you are calling a flue damper). This is a sign of poor draught and or poor or lack of combustion air/cold chimney partially blocked chimney etc. All are bad and need to be addressed asap.

MichaelG · February 2018

Thanks everyone for your comments and advice. I called the oil company and they sent out a technician who seemed very competent. He agreed that the issue was likely delayed ignition and spent about 90 minutes working on the burner.

Reportedly it was running slightly rich and the electrodes were quite out of adjustment. The check valve in the pump was also failing, so the pump was replaced.

Jamie Hall · February 2018

MichaelG said:
...the electrodes were quite out of adjustment. The check valve in the pump was also failing, so the pump was replaced.

That'll do it.

EBEBRATT-Ed · February 2018

@MichaelG , let us know in a week or two if that was the fix.

MichaelG · March 2018

Quick update! Ever since the fella from the oil company worked his magic (oil pump replacement, electrode adjustment), the barometric damper has yet to launch itself across the room again. I guess that's a good sign? Thanks everyone for your suggestions and for encouraging me to get it fixed quickly!

EBEBRATT-Ed · March 2018

@MichaelG

Seems you had a good tech. If he's good hang on to him.

Now you can sleep. Safety is important

Thanks for the update

GBart · March 2018

Aye, I've seen draft regulators go through walls, get it checked now.

Flue Damper keeps flying across the room

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