Pilot takes forever to light

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  #1  
Old 01-10-11, 11:00 AM
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Pilot takes forever to light

My cottage has 2 through-wall NG heaters that use a standing pilot ignition. Each has a ball valve inches away from the gas valve. Both heaters have the same problem in that they take many minutes of holding the control knob in before the pilot will light. It behaves like there's air in the line except 1) the ball valve is so close to the control that a leak couldn't have much affect (an assumption) and 2) my range is much farther down the gas line and it lights quickly.

I've fiddled with the pilot adjustment and this didn't help.

Should I NOT turn off the gas at each appliance when the cottage is unattended for long periods? IS gas flow to the pilot so tiny that it actually does take 3-4 minutes to push the air out of the pilot line??

I'm not exaggerating when I say it really hurts my thumb to hold that button in for so long until the pilot finally lights--especially when it's 20 deg. F inside
 
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Old 01-10-11, 11:31 AM
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No Gas Pro...but I imagine yes it could take that long.

As to the button....try holding it with a screwdriver or dowel...that way you use your whole hand not just the thumb. Of course thats if its location will allow it.
 
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Old 01-10-11, 01:17 PM
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I'd start by taking the pilot burner out,m disassembling it and cleaning the pilot burner and pilot orifice. Getting the pilot orifice out involves removing the pilot tubing at the pilot burner where it connects.

While you have the pilot tubing disconnected, check to see if you have a free flow of gas through the pilot tubing when you push down on the gas valve safety.
 
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Old 01-10-11, 04:30 PM
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On one of them I did take out the ass'y & clean. I thought I had found my problem when I cleared out some rust & scale but it made no difference. I have a good pilot flame once lit. I've considered using a C-clamp to hold the button in until it and will do that if there's no solution to this. I want this to act like the instructions say ("wait a few seconds and push the spark igniter to light"). I don't mind so much but I want it to be easy enough for my wife or anybody else I might let use the place when I'm not there.
 
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Old 01-11-11, 01:24 PM
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If you have a good pilot flame and thermocouple, then you probably need to replace the electric gas valve. The safety magnet on the gas valve can get weak making the magnet hard to hold and easy to drop out.

There is an in line adapter that allows the millivolts to be monitored while the thermocouple is installed on the gas valve. That's the real way to identity what's happening.
 
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Old 01-11-11, 04:12 PM
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Does that have anything to do with what's going on when you're holding in that button to let pilot gas through? Doesn't holding in that button bypass the safety interlock you're describing?
Sounds like that would only affect on/off operation of the valve in response to thermostat demand.
 
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Old 01-11-11, 05:49 PM
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when you adjusted the pilot pressure that will affect how hard/easy the pilot will light. Also, while it was disassembled did you check to see if the gas came out right away with out the pilot tubing hooked up as Seattle had mentioned? It could be a weak or out of adjustment spark ignitor as well. First thing is first, check for gas present immediately when depressing the knob.
 
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Old 01-12-11, 09:50 AM
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I'll try to determine if gas is flowing immediately out of the pilot port. I'm not sure exactly how to do this since I can't get my nose in there close & flow would probably be to low to hear. I have a gas detector but its response time is very slow so it probably wouldn't be much help.

I'm not even concerned with the piezo sparker at this point. I use a long butane lighter or a propane torch to get it lit. I'll check the sparker after the gas issue is resolved.

Since nobody's addressed it I guess the possibility of air filling the valve & pilot tube & taking minutes to be pushed out by gas is a dead end?
 
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Old 01-12-11, 10:44 AM
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Determining adequate gas flow from the pilot tubing is a matter of experience. In general terms, you will have quite a bit coming out. I think you can usually hear it a little bit.

And since the entire gas system is positively pressurized, you don't get air into the system unless it's been shut off and the piping opened to the air.

However, if natural gas has been shut off for several weeks or more, it wont burn and the old gas will need to be purged out of the system. You can hold a match to a pilot light and SEE the gas blowing the flame but not lighting when this condition exists.
 
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Old 01-12-11, 04:28 PM
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Originally Posted by SeattlePioneer View Post
However, if natural gas has been shut off for several weeks or more, it wont burn and the old gas will need to be purged out of the system. You can hold a match to a pilot light and SEE the gas blowing the flame but not lighting when this condition exists.
That might be my problem. Like I said it's a cottage and I turn off the gas at each valve when I won't be back for a month or more. I can see the match flame bending over and that's why I assumed it was air that had filled the line from the valve outward. What I considered odd was that the stove burners would light quickly--but then they flow a LOT more than a heater pilot and simply push the bad gas & air out quickly. They also take awhile to light but it's seconds rather than minutes.
I've never heard that NG goes bad in the pipe.
 
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Old 01-12-11, 04:33 PM
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Is there any way to easily "burp" this old gas from the line to each heater. I realize there's safety issues involved but I think it can be done with low risk.
 
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Old 01-12-11, 07:30 PM
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I asked engineers at the gas utility about this and they said "Huh?"

No one has ever given me an explanation that makes sense ---but there it is --- the gas blowing the match flame!


The simple way is to simply purge the gas through the pilot burner until you get some that will light. If there's a lot of pipe you can disconnect the pipe at a union or flex connector and turn on the gas shutoff valve to purge it out in a hurry.

Leave a wrench someplace handy so that opening the fuel line is easy and convenient and you can save your thumb. You should mix some water and dish washing detergent and soap out the fittings when you are done to verify there are no leaks.
 
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Old 01-13-11, 07:50 AM
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So you've seen this yourself--gas blowing the match but not igniting? I couldn't find a single thing on the internet that says gas has limited "shelf life". Everyone says it lasts indefinitely in the pipe or tank. That's why I always thought the gas had been replaced by air.
 
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Old 01-13-11, 09:12 AM
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Oh I agree---- I've never seen any authoritative reference either. But I've reliably observed the effect.


And there just isn't any way air can be introduced to the system ---it's always under significant positive pressure unless the gas has been turned off ---- and even then it's in a gas tight system.
 
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Old 01-13-11, 04:28 PM
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That's where I'm not so sure. My gas IS shut off at the line leading into the appliance and I don't know what keeps air from entering the open pilot assembly and replacing the gas sitting in there & inside the gas valve--all the way up to the ball valve. I'm thinking at the flow rate gas goes through the pilot plumbing it might take awhile to push all this air out.
 
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Old 01-13-11, 07:20 PM
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The gas valve shuts off the gas to the main burners and pilot tubing.

As a practical matter there is no way for air to get father than the gas valve. Unless you open up the gas fuel line.
 
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Old 01-14-11, 10:53 AM
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Good point and it leads me to believe I'm making a small mistake in how I shut down the heaters. When packing up to leave I usually just turn off the ball valve beside the heater rather than go to the extra trouble to remove the front and turn off the gas control properly. This does leave the control open to air entering all the way back to the ball valve. That valve is only inches away but 1/2" pipe can hold a lot of air compared to the tiny flow through the pilot port & orifice.

I'm still suspicious air is my problem and I'm likely making the problem much worse by not shutting off the gas at the control knob.
 
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Old 01-14-11, 11:29 AM
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No...once the pilot is out the control valve will cut off...blocking the main supply line. I wasn't thinking about that in my first post.
 
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Old 01-14-11, 11:30 AM
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It really makes no difference.

It's really a minor nuisance to purge out the line if you recognize the problem and have the basic skill you need.


The main problem is when people don't understand the problem and spend money for a repairman to come out and light the pilot.

Ideally, you should have two pliars or wrenches to open the pipe union or flex connector at the furnace. Close the shutoff valve, open the pipe and turn on the shutoff valve for a few seconds to put out the stale gas. Reconnect the pipe and away you go!

The two wrenches allow you to "back up" the adjacent fitting so it doesn't turn while you are turning the mating fitting.

For tasks that need to be done from time to time, leaving an extra set of tools where they will be needed simplifies things. In this case I'd leave an extra set of wrenches on top of the furnace or in the burner compartment.
 
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Old 01-16-11, 12:33 AM
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I wish there was such a thing as a gas diverter valve like there is for water plumbing but I suppose whoever decides these things feels it would be dangerous.
 
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Old 01-16-11, 08:36 AM
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The gas line should be designed to be taken apart using a pipe union or a flex connector. If those are there as they should be, purging the line is a simple matter as already described.

Do it once and you should be able to do it with confidence in the future.
 
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Old 01-17-11, 04:11 PM
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It's not a big deal for me--whether I use a clamp to hold the button in or loosen the pipe. It's just that I'd like it to be more "guest friendly" when I'm not there.

I bet I could get the tc good n hot to fool the valve into opening. But again not something I would want a guest to try.
 
 

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