Any gas-geeks around? Problem with gas fireplace

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scuwp

3886 posts

Uber Geek

#171743 29-Apr-2015 17:37

As per subject.

Gas fireplace keeps on stopping. It is an open fire type with a pilot light and a wall switch that turns the main burners on or off. Normally the wall switch results in a distinctive 'clunk' sound when turning on or off, which I assume is a solenoid or similar opening and closing a gas valve.

After a few minutes use the main flame slowly dies down and stops. No noise is heard. When turning the main wall switch on or off there is no corresponding 'clunk'. Pilot light remains lit, no problems there. After it cools down it can be started again and the 'clunk' returns, and so the cycle continues.

I have not yet isolated the wall switch but as it works to turn it on initially I doubt it suddenly has a change of heart. I am guessing there is a valve or solenoid that is buggered and will need an expert to replace.

Am I on the right track? Reluctant to call a tradey in if there is something simple I am missing.

Thanks

Lazy is such an ugly word, I prefer to call it selective participation

mattwnz

20165 posts

Uber Geek

#1293784 29-Apr-2015 17:50

I have got one of thes,e although it isn't mains powered. Mine you have to light the pilot light with a match, and the pilot light is supposed to stay on all the time. If I blow the pilot light out, gas will continue to flow, and will then make a clunk about a minute after, and the gas flow stops. So that clunk I believe is the valve for the gas turning off. I pressume that it is controlled by some form of themostat, so when it drops below a certain heat, it switches off the valve, and it is probably spring action. eg if your power went out, it would need to be able to switch off for safety. So you possibly may have a faulty themostat. It is something you would need to get an expert in to look at. You should also read the instructions to see if your problem is in the troubleshooting section.

ObidiahSlope

260 posts

Ultimate Geek

#1293789 29-Apr-2015 17:56

I can't help you with this problem other than to advise you to exercise prudence and caution.

There is reason that work on gas appliances must be preformed by a gas fitter and these gas fitters must be registered

You don't want to be standing in the blasted remains of your house or standing amongst corpses on your lounge floor because you filled the room with carbon monoxide.

Geeks have a "wonder if I can fix it" mindset but in this case I would get a professional to sort it..

Obsequious hypocrite

scuwp

3886 posts

Uber Geek

#1293826 29-Apr-2015 19:28

Cheers. I definitely wont be pulling it apart. Just wanted to check I wasn't overlooking something simple, given my operating knowledge is little more than a guess.

Lazy is such an ugly word, I prefer to call it selective participation

nolanz

83 posts

Master Geek

#1293831 29-Apr-2015 19:57

It is half a century since I was a gas fitter, but I guess they still have the same features.
In some fires the pilot light plays onto a thermocouple which generates electricity, which in turn is used to hold open the solenoid.
If the pilot light goes out, the thermocouple stops producing electricity and the solenoid closes.
It might be worth looking to see a small metallic probe is being heated by the pilot light, and that it is clean.
It might be that the thermocouple has failed
However it would be unusual for the gas to go down slowly in this case.

Another possibility is that the main burner is drawing the gas and reducing the pilot light flame in some way.

As I say it is a long time ago with old technology.

scuwp

3886 posts

Uber Geek

#1293859 29-Apr-2015 20:32

nolanz: It is half a century since I was a gas fitter, but I guess they still have the same features.
In some fires the pilot light plays onto a thermocouple which generates electricity, which in turn is used to hold open the solenoid.
If the pilot light goes out, the thermocouple stops producing electricity and the solenoid closes.
It might be worth looking to see a small metallic probe is being heated by the pilot light, and that it is clean.
It might be that the thermocouple has failed
However it would be unusual for the gas to go down slowly in this case.

Another possibility is that the main burner is drawing the gas and reducing the pilot light flame in some way.

As I say it is a long time ago with old technology.

Sounds logical. Yes there is the starter probe (or whatever it's called) on one side of the pilot, and on the other a small vertical steel rod, which I am guessing is the thermocouple. The pilot light is going as strong as ever and it definitely heating the rod. I am guessing that a faulty thermocouple is a possibility. Back to calling an expert tomorrow. Cheers

Lazy is such an ugly word, I prefer to call it selective participation

Aredwood

3885 posts

Uber Geek

#1293942 29-Apr-2015 22:50

Most likely it will be either a solenoid valve switched by mains. Or the Robertshaw "Millivolt" system. Both use a pilot and thermocouple to give protection against the flame going out. And a solenoid valve to control gas to the main burner. Only difference is either powering the solenoid via mains. Or with the millivolt system the thermocouple produces enough power to go through a wall switch and control the main gas solenoid valve as well.

Have replaced alot of failed coils on mains operated solenoid valves. And usual problem on the millivolt is the pilot not heating the thermocouple enough. Which will often produce enough power to keep the safety solenoid valve open. But not enough to reliably control the main burner solenoid. And yes have seen cases of the pilot flame getting smaller when main gas valve opens. Causing interesting intermittent problems.

Either way you need a gasfitter. But check that they also do gas appliance repairs. Lots of gasfitters out there who can install gas appliances but who don't know how to repair them. And yes im a certifying gasfitter myself with 10 years experience.