Oven has small explosion igniting and going off. says tj
A few years back I helped a neighbor with this same problem in a forced air, gas fired, "horizontal" furnace in his attic.
After having him cycle the thermostat a couple dozen times while I watched through the opening in the side of the furnace, I finally figured out what was happening.
First, there were about 6 cast iron burners [about 14 inches long with two rows of gas holes along the length]. These burners were parallel to each other and oriented perpendicular to the long axis of the furnace.
The gas was fed to the ends of the burners with a pipe manifold. The standing pilot light was at the center between burners 3 and 4. Due to the spacing distance between the burners, the pilot light was too far from even burners 3 and 4, the flame could not "jump" to ignite them, or any of the other burners. The manufacturer had installed a thin sheet metal "tent" which ran from the gas entrance end of burner 1 to burner 6, and was about 2 inches above the burner, AND the pilot light.
The standing pilot was on all the time. When the gas control valve turned on, gas began to come out of all the burners at the same time. Naturally it came out of the gas supply manifold ends of all the burners.
The "tent" captured that gas coming from the burners and "filled" up to over the pilot light which ignited the gas at that point, and the flame would propagate along the tent to ignite the gas coming out of all of the burners.
In my neighbors case, the tent had somehow become dislodged so that it did not cover all of the burner ends. For those burners which it did cover [including the pilot light] it caused the burners to light properly.
For those burners who's ends were not covered, and who's gas could not be captured, they would NOT ignite simultaneously with the others.
As these burners WERE feeding gas into the combustion chamber, the gas "envelope" would spread until it reached the nearest flame ignition source, at which time the entire "bubble" of gas would ignite with a minor boom [actually a low energy explosion]. Flame would momentarily shoot out of the burner chamber opening, and from that point the furnace would operate normally until the next restart cycle.
Although there could be several causes, I suspect that the symptoms you describe are the result of DELAYED IGNITION of some or all of the main burners.
IF this is the problem, then the solution is to clean all the burners [including the burner outlet holes in the ignition ends of the burners], clean out the burner compartment, AND properly adjust the orientation of whatever system [you have to evaluate how it works from analysis of YOUR furnace] your furnace has to ensure all burners ignite as close to the same time as possible.
When operating properly, the ignition should be a smooth transition, burner by burner, from the pilot to the farthest burners. In other words. the ignition will "flow" from the pilot outward to each adjacent burner until the farthermost ends ignite last. This usually doesn't take more than one or two seconds at the most.
Unless you are an experienced handyman, and understand this analysis and instructions, I strongly suggest that you engage the services of a professional furnace technician.
2/14/2009 12:52:29 AM •
Imperial...
•
Answered
on Feb 14, 2009
