Wall heater ignition issue

307TurboFire

The manual says…Step 5: "Turn gas cock knob to PILOT." Step 6: light the pilot. Step 7: "Push gas cock knob in as far as it will go. Hold it for 30 seconds after pilot lights."

Last used about 2 years ago. On this particular occasion, first time I lit the pilot, it didn't light, so I turned the knob to off to get a better look at it. A minute or two later, I turned the knob back to pilot. This time, the pilot lit, whereupon, I pushed the knob in for probably around 50 seconds, not 30. About 2 seconds after I let the knob pop back out, there was a small THWUMP, i.e., a small explosion about the size and shape of an eggplant, which I perceived began at the pilot and then moved down to the control knob area. When that subsided, there was a small lingering ball of fire enveloping the control knob. I assessed that for a second or two, took a deep breath, blew the fire out, then turned the knob to "off." The windows were all open. I have been assessing at intervals. The gas detector says "0" and I don't smell anything.

I am handy enough to have replaced the low-voltage circuit transformer about 2 years ago, and I successfully operated the furnace without issue after that, until now. However, I do not understand the mechanics of what went wrong here. Was there some sort of build-up of gas around the knob because I had it pushed in for longer than 30 seconds?

delcrossv

How long you hold the pilot knob down isn't material.

Sounds like a leak around the control valve stem. You need a new gas valve.

109A_5

Hello 307TurboFire,

You did not really say what got you to this point ? Is this the first lighting for this season and it has been off since last season ? Was any work done ? Any piping left loose, any pipes cracked ?

On the first lighting of the pilot after its been off for a while it often takes a bit to purge the air out of the line then the " Hold it for 30 seconds after pilot lights " is to ensure the thermocouple is warmed enough to keep the pilot on.

Sound like there is a gas leak that should not be.

307TurboFire

It has been off since last season. Yes, I just wanted to confirm my first thought which is that it probably needs a new valve. Thank you, I appreciate.