Tangent
New Member
Utica M150AGB, Natural gas boiler
There are 3 burner tubes. Sometimes, the middle tube [only] will have a blue flame in the venturi for the entire burn cycle. This happens [randomly] about 5% of the cycles. During the flashback, I can lower then raise the T-stat, and the next burn there is no flashback.
A month ago, an HVAC pro replaced the millivolt gas valve and the aquastat, but the problem is still there.
The burner tube can be displaced a few millimeters closer/farther from the orifice. I tried both extremes. I’ve swapped the left and right burners with the middle one, but the problem is always in the middle position.
Is there a safety issue with a flame in the venturi?
Any other tests I can try?
There are 3 burner tubes. Sometimes, the middle tube [only] will have a blue flame in the venturi for the entire burn cycle. This happens [randomly] about 5% of the cycles. During the flashback, I can lower then raise the T-stat, and the next burn there is no flashback.
A month ago, an HVAC pro replaced the millivolt gas valve and the aquastat, but the problem is still there.
The burner tube can be displaced a few millimeters closer/farther from the orifice. I tried both extremes. I’ve swapped the left and right burners with the middle one, but the problem is always in the middle position.
Is there a safety issue with a flame in the venturi?
Any other tests I can try?