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avionicus · Nov 10, 2007, 09:52 PM

I recently bought a new home that has a Napoleon GD 33NR Gas fireplace in it. This is controlled by a regular light switch (on/off -two wires, black and white). I am trying to connect a Honeywell RTH5100B Digital thermostat (millivolt capable) to it instead of the switch so that while we are in the room we can "manage" the heat.

My problem is that the install manual for the thermostat or fireplace doesn't show which post to connect the two wires for the fireplace to.

Fireplace Connection Label:

TH/TP ------> Black wire

TP

TH ---------> White wire

Thermostat Connection Label:

Rc

R

Y

O/B W

G

Any help with this is greatly appreciated.

hvac1000 · Nov 11, 2007, 09:52 AM

Get a line voltage thermostat with a on off selection switch and mount it to the box behind the wall on off switch area on the wall. This is real simple and keeps you from playing with the wiring in the unit itself. You can get a manual or automatic thermostat that will work on the wall location I mentioned.

avionicus · Nov 11, 2007, 01:07 PM

Originally Posted by hvac1000

Get a line voltage thermostat with a on off selection switch and mount it to the box behind the wall on off switch area on the wall. This is real simple and keeps you from playing with the wiring in the unit itself. You can get a manual or automatic thermostat that will work on the wall location I mentioned.

HVAC1000,

Thanks for the reply,

Can you give me a part number for such a device? Why do I need a "Line Voltage Thermostat" if the Honeywell thermostat I have is capable off working with millivolt systems such as fireplaces like mine? This model of thermostat is a manually operated one, simple on/off and set temperature with a digital display.

Does the thermopile not generate the correct millivolts to operate the fireplace with a thermostat vice a switch?

I was going to connect the wire from the TH/TP post on fireplace to the R post on thermostat and the wire from the TH post on the fireplace to the O/B W post on the thermostat. Just need ed to know if this would be a correct combination?

Thanks,
Avionicus

labman · Nov 11, 2007, 01:17 PM

Those black and white wires at the wall switch, are they the typical little 18 gauge thermostat wires coming from the fireplace? If so, I see no reason why what you are suggesting shouldn't work.

biggsie · Nov 11, 2007, 02:16 PM

Look under Product Recommendations -- top thermostat -- line voltage

Honeywell TL8230A1003 Line Voltage Thermostat

My concern is placing thermostat near fireplace -- most are placed away

From heat source -- Usually an inside wall

hvac1000 · Nov 11, 2007, 02:57 PM

All I was doing is try to make it simple for you to hook a thermostat up that would work great without all the rewiring of your fireplace wiring. Usually the fireplace milivoltage is dedicated to operating the valve with nothing left over to power a thermostat with long wires attached. Doing it the way I suggested also would mean that you would not have to run a separate wiring line and bust a hole in your wall for the new thermostat mounting (rework box) and operation wire.

I guess you can take the horse to water but you cannot make them drink. LOL. Good luck with your project weather you do it the easy or hard way.

labman · Nov 11, 2007, 05:08 PM

I see nothing in your post that really suggests what voltage you have at the switch. Black and white wires are common at many voltages. Since you mentioned that the thermostat you bought was millivolt capable, I assumed the wiring at the switch was part of a millivolt system. If so, if it worked with a manual switch, I see no reason why it shouldn't work with a thermostat.

If the wiring at the switch is part of the 120 volt feed from the house to the fireplace, only then would it be easier to use a line voltage thermostat.

avionicus · Nov 11, 2007, 06:12 PM

Thanks to all for replying,

1. There is no household power to the fireplace, I light the pilot light the same way you do a BBQ. The fireplace is controlled by a single throw switch on a wall located across the room from the fireplace, which as I stated before is connected to the fireplace control valve via an approximate 12-14 ft run of 18 gauge wire (2 wire, black & white).

2. The 18 gauge wire is connected to the control valve as indicated in my second post.

3. I just need to know which post on the thermostat I need to connect the wires to based on where they are connected.

Please see attached pics for further clarification.

Thanks,

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hvac1000 · Nov 11, 2007, 06:15 PM

That should work fine. I thought you had a wall switch for 110 volts. Woops.

labman · Nov 11, 2007, 08:06 PM

As I said in my original post, it should work.

hvac1000 · Nov 11, 2007, 08:34 PM

Originally Posted by labman

As I said in my original post, it should work.

Yes you got one correct. Congratulations and a good job labman. We never hooked them up that way because the ones we used had a blower and they were always on a wall switch for service disconnect. Learn something new everyday.

avionicus · Nov 11, 2007, 10:22 PM

HVAC1000, Labman, and Biggsie,

Thanks for all your assistance, I will give it a try tomorrow and let you all know how it goes.

Avionicus :)

avionicus · Nov 12, 2007, 08:40 AM

Everyone,

I connected the thermostat as proposed and everything works like a charm! My wife is happy, and that is all that matters!

Thanks- again,

Avionicus

HyprMylr · Nov 19, 2014, 05:35 PM

I just tested mine out and found that the B and W connections worked perfect for wiring a thermostat to my fireplace. The best part is that it's idiot proof; B for black and W for white. Enjoy not having to buy anything else!