Fire place repair

Change the Burner switch and thermopile

The fire place bothered me for quite a period of time since I found the main switch can't make the fire place burning.
I thought it is a big issue, I have to call a gas man to repair it. But after I am so disappointed by calling the professionals, I started to study on the issue.

My one is a through fire place. There are 4 doors on both sides. The circuit is something like the following. When a door is open, the circuit is open. Of cause, you can't light the fire place. So I have to figure out the problems one by one.


fig 1. Circuit diagram

I wired directly to the gas valve without 4 door connecting switches. I found the main wall switch (Burner Switch) doesn't work properly. I bought a cheapest new toggle switch. It works much better than the old one. So the burner switch need to change. I put the 2 wires on the burner switch connected directly. It works as good as the new switch. So it means 4 door connecting switches are good.


fig 2. Burner Switch
A milivolt switch should be used for fire place gas valve control. A normal switch can be used. But it will fail in about 1 year. I don't know if this old switch is an milivolt switch or not.


fig. 3 door connecting switch
All 4 door connecting switches are dirty. But they work well. I supposed to repair the switches once a while.
 

fig. 4 New toggle switch
This new switch is only $1.30. I know it won't work long. But I haven't got a real milivolt switch so far.
 

fig. 5 Gas valve
After changing the new burner switch, I can light the fire place by switch on. But it doesn't work sometimes. And I need to turn the switch off and turn it on again to make the fire burning. I think there should be something wrong with the thermopile or gas valve.
 
fig. 6 Gas valves
The gas valve is controled by the power from the thermopile. But it needs at least 450mv (open circuit). I measured the got the result of 370mv on the thermopile terminals. So I believe the old thermopile is weak. It is said that the thermopile will get weak in about 10 years.
 
fig. 7 Old thermopile
Ther thermopile create milivolt power from the heat. The pilot heat the thermopile. So it generate max 750mv electric power.

 
fig. 8 New thermopile
I bought a new thermopile. Since the wire can't touch any metal, I cover the wire by electric tape.

 
fig. 9 Installed new thermopile and pilot light
The new thermopile is installed. The one beside is the pilot.

 
fig. 10 Wire of the thermopile
Make it sure that the red color wire is always in the middle of the gas valve terminals. I measured more than 500mv for the new thermopile. I didn't measure it again. I believe it may reach 600mv-700mv. Since 450mv is enough to power the gas valve, I don't care how high it may reach.

 
fig. 11 Happy fire place like NEW.
Only turn on the burner switch once, the fire place burns. I successfully repair the fire place which I thought it is a big issue and suffered the repeating switching for two years.