[mustang64]

Is it possible to add a thermostat to a unit although it originally did not come with one??

 

[how]

Usually only fireplaces with powerpiles can handle the extra electrical resistance of the added thermostat & gas valve connections. There is also a limit to how long a length of thermostat wire you can run.
Older units with only thermocouples supplying the power.....can't use a thermostat!

I'd suggest supplying us with close up photos of your gas pilot and the electrical connections at the gas valve.

 

[mustang64]

Here you go.

 

[mustang64]

Another photo.

 

[how]

If you get at least .400 DCMV between your two TP gas valve connections when the gas valve is not in the "on" position, then you should have enough power to run a thermostat circuit up to 20 ft. with 18 gu wire.


Take the red line off the gas valve TH connection and connect it to one of your two new thermostat lines.
Take your other thermostat line and connect it to the TH connection on the gas valve where the red wire formally was.

This will allow the gas valve to be controlled by the thermostat while keeping the safety limit circuit intact.

Make sure all the wiring connections at the gas valve and the thermostat are tight and that your connection of the red wire to the stat wire is both tight & well insulated against touching any grounding metal.

 

[supers05]

If you get at least .400 DCMV between your two TP gas valve connections when the gas valve is not in the "on" position, then you should have enough power to run a thermostat circuit up to 20 ft. with 18 gu wire.


Take the red line off the gas valve TH connection and connect it to one of your two new thermostat lines.
Take your other thermostat line and connect it to the now empty TH connection on the gas valve.

This will allow the gas valve to be controlled by the thermostat while keeping the safety limit circuit intact.

Make sure all the wiring connections at the gas valve and the thermostat are tight and that your connection of the red wire to the stat wire is both tight & insulated against touching any grounding metal.

Just to add;

This will NOT power a stat. So any stat that runs off r+common are off the table without extra wiring. (this includes the nest and ecobee) You will have to use a stat that will work solely off of batteries. (many Honeywell stats, sensi, etc.

Cheers!

 

[how]

@supers05

Yes..I was assuming that he was just going to use a simple mechanical thermostat.
Old school habit.

 

[user_12345a]

Mechanical stat is best.

Actually an old school mercury switch stat is best if you can still get one; the contacts of mechanical switches can oxidize over time, causing a voltage drop. It's insignificant on a 120v or even 24 circuit, but for something running on <1v could cause erratic operation.

 

[lenaitch]

I was asking my dealer the same thing a while back and he said they have an aftermarket thermostat with remote. Apparently the 'receiver' replaces the on/off toggle switch. Didn't get the brand and I haven't got around to looking further into it. Our problem is there is no reasonable was to run a hardwired thermostat. Our unit is an older Napoleon.

 

[supers05]

Mechanical stat is best.

Actually an old school mercury switch stat is best if you can still get one; the contacts of mechanical switches can oxidize over time, causing a voltage drop. It's insignificant on a 120v or even 24 circuit, but for something running on <1v could cause erratic operation.

I've seen more then enough fireplaces just like the OPs that use a regular toggle switch. The wires and terminal plates on a plain Jane toggle switch corrode much sooner then the contacts. (a bit of filing and it's good as new)

Cheers!

 

[user_12345a]

Was assuming a t-stat is a given; was just saying that mercury style switch would probably be better than mechanical snap action. I don't think they make mercury stats any more; they wouldn't pose a problem if people disposed of them properly.