Ok got a burner question

Charlie from wmass

I have a Smith GB200 5 section boiler, Atmospheric vented with a functional damper and I installed it one owner back myself. The burners on occasion light off inside the tubes. Never when I am there only when the boiler is recovering from a setback. Chimney was cleaned and inspected this past fall. The combustion numbers were fine two weeks ago when I was there last but the refractory was leaning into the fire chamber. The front and back sheets had the washers rotted off to the cotter pins. The burner tubes looked perfect. No blockages and the gas pressure was spot on. any ideas?

Tim McElwain

That is what is called

"Flashback" if it occurs when a call for heat takes place it often means simply an adjustment to primary air to close up the air shutter slightly. The flame velocity is exceeding the flow velocity of the burners. If it is not eliminated it will damage the burners if that has not already occurred. Smith boilers tend to have very high temperatures down in the burner area which can also cause this this to happen. What are your draft readings? Is the vent damper right after the draft hood?



The fact that there is some damage that has occurred in the chamber could also be the cause. That will be a lot harder to solve.



I assume this is natural gas?

Charlie from wmass

It is natural gas

I will see if I can shut down the air shutters and keep the CO/CO2 levels within parameters. This is the second Smith in a month with issues with the fire insulation loose due to the washers burning off. The last one was shutting off due to the roll out switch being tripped as the insulation was laying down across the burners on that one. That boiler is about a year old than this boiler.

Charlie from wmass

one more factor

In my area, the gas company adds diluted propane to the gas mains; especially in the winter. Not sure if this changes things. I know propane is heavier than natural gas.

Tim McElwain

Yes Charlie

mixing propane really screws up burner adjustments and can cause much higher heat exchanger temps along with light off issues, There is not much you can do other than sort of weather it out. They usually only do that during extreme cold times so it should clear up. I would look into the damage inside the chamber with Smith, that should not be happening obviously.



During my days with the utility when we mixed propane we worked a lot of overtime just trying to keep the burners stabilized.

Charlie from wmass

Tim do you think

since the home is a few miles from the injection plant that it is left over propane from the colder months just getting out to the end of the line? I am still waiting on a call back from Smith.

Tim McElwain

Very unlikely

that would happen. Is the gas company Baystate now Columbia by any chance?



When the mix is done they run it through compressors  and mix air with the propane it is called "Propane Air" in order to try to get it as close to natural gas characteristics as they can. It is usually mixed very well and should not have any residual left over.



Most gas companies have gotten away from doing that and are using LNG for their "peak shaving" times (high gas demand due to low temperatures).

Charlie from wmass

No Not Columbia

This is further west. Berkshire gas. The boiler ran fine today as per customer. It is a pride thing since I installed this boiler I do not like it not running right.