OK I have a hunter fireplace hw21 I think on the gas valve there is th with ph under it and another th beside on the honeywell thermostat there is a r and w what gets hooked up where . And is there anything that needs to be unhooked

Most likely you have a power pile system on your fireplace. The first thing you will need to do is to make sure you have a millivolt thermostat. If you try to use a conventional 24v thermostat it will not work.

Can you tell me what wires are hooked to the gas valve. Is there a red and white that are covered by a silver braid. If so, then you have a power pile system. I will help you figure this out if I can.

Yes it is a power pile and yes the thermostat is a 750millivolt heat only

Okay, please look very closey at the marking at gas valve terminals, I need to know exactly what letters are where. If you could take a clear picture of the vavle leads, it would help immensley. Normally on a power pile valve, you will have three spots to connect wires, they usually read: th, th-tp, tp. Even if you could give a rought scetch of what your terminals on valve look like that would help.

If indeed your valve reads, th,th-tp,tp. Then one wire from power pile goes to tp, the other goes to th-tp. Then one wire from thermostat goes to th, and the other goes to th-tp(which will also have one wire from power pile). Please let me know if this helps. If not, then we will figure it out, but I would need more specifics as to markings on gas valve. Good luck, take care,

Lee

OK here is some pics of the valve

I only see two connection points on the valve. Am I seeing it correctly. It also looks like the temperature setting knob is located directly on the valve, Yes? If so, this unit is not set up for use with an external thermostat. Sorry, there just isn't any way to use a thermostat if what I just said is correct. Please let me know.

There is no temp sensor there is a hi and lo knob
And a fan control
That is why I want the thermostat
There is a toggle swich that says manual or auto that is how I curent ly turn it on by swiching this from auto to the manual

I am not experienced in gas fireplaces at all but allow me to think outside the box. Couldn't you wire in a temp control in line with this toggle switch he mentioned?

The toggle switch may have changed my answer. Can you tell me where the wires from the toggle switch go? And what does the fireplace do when on auto vs manual? What controls the auto function. I still only see two connections on gas valve I the picture. Am I not seeing something. If there are only two connections on the vavle. Then thermostat is not likely usable. But, are there any other wires going into vavle at another location. The vavle you show looks lilke there is something broken off at the terminals. Can you confirm this.

Currently there is 5 wires going to the valve

3 in the top
One middle
One on bottom
Now when the switch is in auto nothing is hapining just the standing pilot
When I switch it to manual it lights up
I think the switch is wired to the valve
One lead in top one lead in bottom
It's kind of hard to see in behind where the wires are

So again I ask, why can't you wire a stat in series with the switch, leave the switch in manual and have it controlled by temp?

Yes, this can be done. I couldn't see the first (top screw) in the pics. Please take one more clear pic.

Put red wire to middle screw. Put white wire to bottom screw. See if this works. Make sure to check for correct operation of thermostat..

Do you have the owners manual for this unit? If so it will give a wiring schematic.

I have a manual but it doesn't have wire diagram

Try what I suggested in post 13. Or there may be a number you can call in the manuall. They should be able to tell you how to wire it. I believe wiring the way I suggested will work.

It seems to be working in reverse if I turn up the t stat it goes out if I turn it down it comes on

Try unhooking wires from thermostat and touching them together. Please let me know what happens. When the wires are touched together the flames should come on. When apart the flames should go off. If it is opposite, let me know. We are getting closer, just bear with me. You did say the thermostat was a heat only 750ml compatible thermostat didn't you?

I just reread all post. Try putting one thermostat wire on top gas valve lead, and one thermostat wire on the bottom gas valve lead. If this is indeed where you auto/ manual switch wires go, then this will work. Your manual on would still turn the fireplace on. But when switch is on auto, the thermostat would control the fireplace.

Very important,, you need to make sure auto/manual switch wires do not go through any other limits or controls before hooking to gas valve. If they do, you will have to splice in one of the thermostat wires before limits, or controls instead of hooking directly to gas valve. We will get this thing, just need to do it correctly.

OK that has seemed to work but I have a small issue it seems that for some reason the fire place doesn't always start up when the thermostat calls for heat. And other times it doesn't start up

Can you clarify how it worked? Did you wire it the way I suggested in post 18? If so, and it works through the thermostat sometimes and sometimes not, then you need to look at a couple of things. How long are your themostat wires? I know you said you had a millivolt thermostat, but are you one hundred percent sure that it is millivolt capable? You also said you replaced power pile. So, if power pile is good, and thermostat is correct, then wires from fireplace to thermostat may be too long. You are limited on how long the wires may be on a millivolt system. Could be a bad gas valve, but there is a way to test it. Please let me know where the thermostat wires are currently hooked that is making it work sometimes. It one on top and the other on bottom? If so, just take a piece of wire and jump the top and bottom terminals, see if fireplace comes on, if so, then unjump, fireplace should shut off, do this a few times making sure it turns on and off. If it does, then problem is in thermostat or wires.