# Simple wall switch for Heat-N-Glo for SL-950TR-C?



## slingblade01 (Dec 19, 2017)

Hi,

My fireplace was fully installed in our house with the exception of a wall switch.  The box is roughed in with 110v and wiring to the fireplace.

Is the wiring to the fireplace low voltage?
Does it require a special switch?
What is the model number and where could I find one?

The manufacturer is trying to sell me a remote thermostat switch.  Too fancy and expensive for my needs. 

Feel free offer any advise.

Thanks


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## coaly (Dec 19, 2017)

Wall switch for fan or main burner?


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## slingblade01 (Dec 20, 2017)

coaly said:


> Wall switch for fan or main burner?


 
Main burner


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## coaly (Dec 20, 2017)

Wiring diagram is on page 53 of your manual.

The voltage created by the thermopile (heat from pilot) is what opens the gas valve when a complete circuit is created from thermopile to gas valve. (electro magnet in valve) Notice the red wire from thermopile is connected to center terminal on valve and white wire is connected to left terminal. When the left and right side terminals are connected the burner should come on. (when the thermopile is hot and generating enough electric voltage)

Since this a is very low voltage, wire size is critical. Just because it is low voltage doesn't mean you can use thin thermostat or "bell" wire. The resistance cannot be high between the two terminals from long wire runs, so use a heavy gauge wire for longer runs. The current has to go from the thermopile all the way to switch, through contacts and all the way back, so the distance the current travels is double from valve to switch. The switch can be a thermostat as well, but make sure the points stay very clean if you use that kind of switch. Make sure you use a *millivolt* thermostat.


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## slingblade01 (Dec 20, 2017)

coaly said:


> Wiring diagram is on page 53 of your manual.
> 
> The voltage created by the thermopile (heat from pilot) is what opens the gas valve when a complete circuit is created from thermopile to gas valve. (electro magnet in valve) Notice the red wire from thermopile is connected to center terminal on valve and white wire is connected to left terminal. When the left and right side terminals are connected the burner should come on. (when the thermopile is hot and generating enough electric voltage)
> 
> Since this a is very low voltage, wire size is critical. Just because it is low voltage doesn't mean you can use thin thermostat or "bell" wire. The resistance cannot be high between the two terminals from long wire runs, so use a heavy gauge wire for longer runs. The current has to go from the thermopile all the way to switch, through contacts and all the way back, so the distance the current travels is double from valve to switch. The switch can be a thermostat as well, but make sure the points stay very clean if you use that kind of switch. Make sure you use a *millivolt* thermostat.



Coaly,

Thanks for taking the time for explain how the circuit works.   To clarify, the thermopile creates its own current?  So theoretically, any switch should work?

Why did the installer run 110v into the switch box as well?

Also, the low voltage wire looks fairly heavy...maybe 18 gauge. It looks like basic speaker wire.  Will this be sufficient?


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## DAKSY (Dec 21, 2017)

There should be a coil of 18Ga wire from the factory already attached to the gas valve. 
This gauge wire is good for runs of 25 FEET or less. There is no polarity so it can be connected 
to a standard wall switch without worrying which screw the wires are connected to. 
NO household voltage (ie 110v) should be to the gas valve, or you will SMOKE it.


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## coaly (Dec 21, 2017)

Yes, a thermocouple is the small probe looking thing that the pilot heats and it has dissimilar metal rods inside which bend and touch when heated. This causes electrolysis or a minute current flow. This current energizes the electromagnet in the safety valve holding the safety valve open allowing gas to flow through pilot. (That's why you have to hold it open when lighting and hold until hot enough to generate the current that holds the safety open) This generates 25 to 35 millivolts of DC current which is .25 to .35 volts.

A thermopile works on the same principal and is a series of thermocouples that generate about 75 millivolts which is .75 of a volt. It can be more, but usually around 1 volt. This current is used to energize the electromagnet that opens the main gas valve. The thinner the wire, the more resistance to flow so the magnet is not strong enough to pull the main burner valve open. Clean connections are a must.

110v should only be for a blower when equipped.


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