Gas burners will start, but won't restart

edg2103

I have a Green Mountain gas boiler. My cellar flooded, so I replaced the gas control valve and disassembled and inspected the burners. When I reassembled it, it turned on perfectly with no issues with a clear blue flame. But the odd thing is, when the thermostat sends a signal to turn it off, and then sends a signal to turn it back on, it won't turn on. I'll hear a slight frothing or hissing noise, but the flame will not turn on. A faint orange flame is visible from the burners. 

The only way I can get a strong blue flame again at that point is to shut off the gas manually, cut off electricity to the boiler, then turn it back on and open the gas valve again. At that point, I'll get a clear blue flame again.

Actually I just noticed something else strange. When the burners are successfully on, the boiler makes a buzzing/humming sound that fades in and out. Is that normal?

I'm stumped. Anyone have ideas what i did wrong?

UPDATE on 21 November: I replaced the gas valve again, as well as the pilot tube, but the issue remains exactly the same...

Jamie Hall

Basically... yeah. Anything related to the burner -- controls, valves, tubes -- if it got flooded it gets replaced. No exceptions. If in doubt, throw it out.

edg2103

I did replace the valve though. And that's when the problems started.  This had happened to me once before and I replaced the valve with no issues. This time I don't know what happened..

Mad Dog_2

I've had similar issues with the Green Mountain Electronics a few years back..  "Something" is telling the gas valve bad information.  I would change the Mother Earth 🌎 control, i.e., The Uba, Main brain.
Funny thing is, there was no flood and fortunately it was still under warranty, but I had to isolate the problem, purchase the controls and then get reimbursed.  Mad Dog 🐕 

Steamhead

I'd bet the gas valve isn't turning the pilot completely off. On the next try, the ignition module senses the still-present pilot flame and won't start. Try just turning the valve in the gas line off, then back on, and see if it restarts then. If so, that new gas valve is probably bad.

Mad Dog_2

I see way too many new gas valves go bad in a year AND out of the box.  I've also seen many NOT be adjustable on the main GV or the PV..Mad Dog 🐕 

mikespipe

Just a thought . did you blow out the pilot tube. I've run into the problem with floods water in the tube can cause problems . you would think if it worked for a while it would dry it out

edg2103

Thanks everyone. Yes the pilot isn't going completely off when the thermostat turns the power off (or when I turn off the gas burner emergency switch).

Turning the gas on and off alone does not restart the boiler...I need to turn off the gas and the electric switch. I'll try blowing out the pilot tube when I'm home again, thanks.

I appreciate the help!

EBEBRATT-Ed

Sounds like a bad valve.

Post some pictures of the valve and the gas controls

edg2103

Hi everyone. I bought a *SECOND* new valve and a new pilot tube. The second new valve is less noise, but the problem persists. To recap: When it hits the temperature on the thermostat, the gas turns off, but not completely...there is a faint flame that remains on. I have to turn off both the electricity AND shut the ballcock to get it to restart. I'm stumped.

edg2103

I replaced the electronic controls too, still having the same issue. Any chance it could be the pilot assembly? Something else?

JUGHNE

Did you ever remove the drip leg from the gas line and check it for debris?

It could be rust flakes inside the pipe that lodge under the NG seats in the valve.

And then the really obvious, what way does the arrow on the bottom of the valve point. Should be towards the boiler of course.....almost an insult to ask, but...

I have read of gas valves installed backwards and they still worked....most of the time. FWIW

edg2103

I feel really stupid now. I actually figured it out on my own before reading your message, but yes...the valve was backwards 😔. It makes sense, since the main gas to the burners did cut off, but not the gas to the pilot tube (because when the gas valve is backwards the pilot is upstream from the valve).

I don't know how I did this after successfully doing this same replacement on my boiler several times before....wow that was stupid.

EBEBRATT-Ed

@edg2103

Good @JUGHNE for pointing this out. We have all been their at one point even if some don't admit it I will.

JUGHNE

So did that fix it then?

Ed, I have come close to doing that myself.

But have reversed pumps,(that can be a head scratcher....seen it here a few times).

Check valves....you know right away.

Curb stop valves with the drain back.....get wet right away. Look around to see if anyone saw that!

Seen a project with NG stops that included the 1/8" test port....all 8 of them installed backwards.

109A_5

EBEBRATT-Ed said:

Sounds like a bad valve.

Post some pictures of the valve and the gas controls

The clue.

edg2103

@jughne everything working perfectly now. Thank you!