Burnham Steam Boiler Backfiring?

badgergrrl

We have a Burnham steam boiler in our house that has been backfiring on and off this winter. (Pretty sure that's what it is, a boom, loud enough that we worry someone or something has hit the house, followed by the a burnt smell.) This usually happens when the boiler tries to light after having been off for a period of time (when we return home from work, etc.) It then fires up normally a couple of minutes later. Initially, we had the repair guy out and he replaced the valve for the water filling mechanism, but inspected the rest of it and said it was fine.



It just did it again, any thoughts on what could be the cause? We have heard some rustling in our flue pipe - I wonder if an animal got trapped in there. The tech did remove the flue at the boiler and did not find any obstruction. Could that be playing a part?

Steamhead

It shouldn't do that at all

is this an oil or gas boiler? 

badgergrrl

Addendum

Sorry - forgot that part. It's natural gas.

Steamhead

Get a different tech out there

You may have a situation where gas is being fed to the burners before ignition takes place. You need this fixed YESTERDAY. My money would be either on the gas valve or maybe the control module.



Try the Find a Contractor page of this site. If you're in the Baltimore area, contact me.

ed wallace

backfiring

why did tech work on the waterfeed when its a gas delivery problem ? I am thinking same thing as steam head not good to have a backfire he should have checked the gas valve and the gas tube that gets gas to the burners could be a case of water in the gas line

badgergrrl

water

There was a problem with the valve going into the automatic fill, and it caused the boiler to shut off. (I blow it down and check the water level once a week (Sunday), but the backfire occurred on a Saturday.) He replaced the valve and said everything else was clean. I'm unclear myself, unless there is residual gas during a failed ignition? (Similar to the old gas stoves when a pilot light is out?) I really have no clue.



After the comment I read from Steamhead, I turned off the boiler and shut the gas valve off inside the unit. I will call a different company on Monday (in Wisconsin, probably a bit of a drive for you Steamhead, but thanks for the offer!) - and get out some sweaters. Of course this would happen during a lovely spring cold snap!

badgergrrl

more detail

More details: we have had three backfires (that I know of - my husband swears he has heard it once or twice when it kicks on in the morning, but our bedroom is on the second floor, boiler is in the basement and we live on a very busy street with trucks and a couple of potholes, so it's hard to say.)



first backfire(xmas-ish): The water level got too low and the boiler shut off. I manually added water, and turned boiler off (just the power) for 15 minutes to reset. Turned it back on. When it fired - whooshy! Chalked it up to not shutting off the gas during that 15 minutes. (I've always cooked with gas and figured it was similar to when you turn on a burner without igniting it accidentally, then go back and ignite it.)



second backfire (month ago): We had heard an animal in the flue pipe. Saturday night, heard a large boom and then smelled combusted gas-burnt smell. I got nervous and shut off gas to boiler and boiler itself. Tech came on Monday and took apart vent to flue, no animal, no nesting material. (Flue vents into empty chimney.) He replaced valve to automatic filler and boiler had been igniting and filling fine ever since. Until.....



third backfire (today): No idea. Water in sight glass is about a third of the way up, past the shut-off point. Heard explosion and smelled burnt again, about five minutes after, boiler fired up just fine. (As I said, though, I have since shut it down due to comments received.)



So far, the only common denominator seems to be the length of time before ignition. As I said earlier, it only seems to happen when the boiler tries to fire after having been off for a long-ish period of time. (During day, we have the thermostat set low while we are gone, and overnight as well.)



Does this confirm the "water in gas line" theory? Or add another option to the mix?

Is this a difficult fix?



Thank you all so much for your help!

Steamhead

Does this boiler

have spark ignition- that is, you hear a buzzing sound when it comes on, which then stops and the main burners light off? 

badgergrrl

Ignition

I don't believe so, but what are my other options? Here's a photo, if that's helpful... (I have no idea why it's rotating the image.)

Steamhead

Yes it does

the box on the right side with all the wires coming off it is the ignition control module. It not only generates the spark, but monitors the ignition and operation of the burner, shutting it off if something goes wrong.



Both the gas valve and the module appear to be standardized parts.

badgergrrl

Ignition?

Is the ignition possibly a culprit?

Steamhead

Don't know yet

a pro would have to make some tests to determine what's going on.