honeywell standing pilot gas valve
hello every one
the pilot will not stay lit,changed thermocouple,no success.what else can i check?
thanks for any help
Sounds like there's a loose connection with the safety electromagnet, and it's time for a new gas valve.
Either that, or it could be that your clothes dryer is causing a draft of air into your house through the chimney and blowing out the pilot.
You see, a gas valve can be though of as nothing more than two electromagnetic valves plumbed in series. The small pipe that carries gas to the pilot light takes gas from IN BETWEEN those two valves. So, as long as the pilot light is lit and the thermocouple is providing sufficient power to the first valve, gas continues to flow through that first valve to the pilot light. Only when the second valve opens does gas also flow to the burner trays.
On a water heater with no external power supplied, then the pilot light is used to provide the electricity top operate both the first valve (called the "safety" valve) and the second valve (called the "main" valve). In that case, a "thermopile" is used instead of a thermocouple to provide more electricity than a thermocouple would. A thermopile is really nothing more than a few dozen thermocouples all connected in series, so that it produces about 1 volt rather than a few millivolts.
On a boiler or furnace there will always be external power available. That's cuz the boiler needs 120 VAC to operate a circulating pump, and a furnace needs 120 VAC to operate the blower. So, on a boiler or furnace with a standing pilot, then a transformer is used to provide 24 VAC power for all the boiler and furnace controls. That 24 VAC from the transformer is also used to provide the power for the main electromagnet in the gas valve. In that case, the electricity from the standing pilot is used to hold the first valve (the safety valve) open. The second valve (the main valve) operates on 24 VAC. In practice, 24 VAC flows in a series loop through all of the safety devices to the electromagnet on the main valve. That if any of the safety devices breaks the circuit, the main valve closes and shuts off gas flow to the burner trays. But even if one of those safety devices was tripping and disrupting the flow of power to the main valve, it wouldn't affect the flow of gas through the safety valve to the pilot light.
I'd have someone turn on your dryer while you watch the pilot light flame, and see if opening a window prevents that pilot light from being blown out.
Alternatively, it could be that the thermocouple wasn't properly positioned in the flame, or that you didn't make a good connection at the gas valve.
You DO NOT use any teflon tape or pipe dope on the threaded connection where the thermocouple screws into the gas valve. That would just interfere with the electrical continuity between the thermocouple and the electromagnet. The copper "wire" that connects to the end of the thermocouple is actually a co-axial cable with an outer copper jacket and an insulated inner copper core.
If the thermocouple is right in the flame and producing sufficient voltage, and you've got a good connection at the gas valve, then the only other thing would be the safety magnet closing and shutting off gas flow to the pilot because of a loose or bad connection right inside the valve. In that case, you're needing a new gas valve.
If you have a DVM and a candle flame, check the old & new 'couple outputs; 28 mVdc is probably the minimum.
Depending the 'couple's rated voltage you can make a 'couple simulator from flashlight cells and two resistors from Radio Shack.
Can you clarify the problem? Is it that the pilot is not staying lit, or the stove will not light?
The thermocouple should not have any effect on the pilot staying lit.
If it's the first (not staying lit), you probably need to increase gas flow to the pilot if you can.
If it's the second, it could be a bad or mis-matched thermocouple, or a loose connection to the safety valve (that happened with mine)
Wow, Nestor. . .I like your understanding of pilots and gas valves!
I have a unique problem that I'm not sure you answered in the above post:
I have a pool hot water system with a Honeywell #003900F gas valve controlling gas flow.
Every day, after the Circulating water pump and heater are supposed to go on, and when I go out, the water heaters pilot igniter is sparking but no pilot flame is coming on. But, if I reset the gas valve by pushing the center manual reset clockwise to off then back on again, the pilot igniter sparks and lights. . .and stays on until the thermostat says enough. But once the valve closes the problem reoccurs. . .
This is the only consistant way I've found to turn it on.
So if all the safety checks before the valve are go, just what is happening differently when I reset the valve? Do you think the valve is bad?
Many thanks for your thoughts.
Take some emery cloth and clean the flame, or you can use fine sand paper.
The enter blue flame of the pilot flame should be burning around this flame rod. Do this and see what happens. later paul
Thank you for your response, Paul.
The only way i thought I knew that the thermostat was working is that if i turned it down enough, the ignition spark would go off and then if i turned it up, it would start again. . .but never any pilot flame unless I reset the gas valve. I'm not sure how I would know if it is kicking out on safety. . .
I never bothered, perhaps wrongly, to suspect the pilot flame, because when it does come on with a gas valve reset, it never fails and burns an almost colorless blue that turns the thermocouple (?) red immediately and allowing the burner to fire. So under these conditions, can you imagine that the flame rod needs cleaning? The question is "what's different about a valve reset and a valve turn-on as the result of the call for heat by the thermostat?"
I am getting the impression, this morning, that the temperature in the pool is creeping upward with my meddling of resetting the gas valve when I hear the ignition sparking and have had to simultaneously also turn down the thermostat as a result of the warming. So there is a likelyhood that the thermostat may not be satisfied all the time. . .but the safety mechanism shouldn't be turning off the gas in this situation, would it?
does not have a wire, it screws in the gas valve. A flame rod get a film build up on it that you can not see, and the more film build up it get the more it will
mess up and put the unit out on safety. In a flame rod pilot system, the pilot flame makes a electric connection from the pilot to the flame rod, thats why i asked you to look at the pilot and make sure the flame is not lifting off the burner head, if it is you will lose some electric power.
if the thermostat is not satisfied then it could be tripping out on safety and that is why you have to reset it. It could be your gas valve is getting bad but it a lot cheaper to check out the pilot and clean the flame rod first. More units are stopped by dirty flame rod than any thing else. Later Paul
I took a picture but don't see an easy way to upload it here. . .
Thanks for that description. . .It is definitely not a Thermocouple. . .I've lived too long and misspoke. . .But. . .I actually don't see a rod. . .
I just see a fork that is the object of the flame. . .then a source of spark in front and below it. . .and then the pilot opening with a shovel shaped flame director over it that is the object of the spark. The only wire is to fire the ignition spark. . .
The "fork" just appears to be grounded. . .
I emery-ed off the Fork and pilot still not lighting. . .
I don't understand how reseting the gas valve could always stop any flame liftoff when under normal circumstances it almost always happens? Plus, the pilot, after gas valve reset heats up the 2 pronged "fork" to redhot instantly.
I will try cleaning up the fork one more time and check in the dark with better flame visibility for the "liftoff". I'm starting to think that the thermostat is not being satisfied but why would the safety turn off with just a spark or is it on a timer?
You are so right about valves being expensive. . .!
Thanks for stepping up to the plate on this, Paul. . .winter is coming and I don't want to have to nurse this like a herd of milk cows. . .
I wonder if this works for a picture of the pilot assembly. . .terry
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