Gas millivolt wiring 

Thanks for the support. More coming. GFM

thanks for the support GFM

I just started working for a HVAC company who is the only company in my area who works on fireplaces that they didn't install and I never learned anything about fireplaces in school so your videos are very helpful.

thanks gray man, had a service call today on a wall heater. wasn't sure why it wasn't working from the stat but I think you just explained it to me.

Awesome video. I had no idea how my tstat was making my boiler fire without a transformer! Now I know

Thank you grayfurnaceman. Been watching your videos and not only did I save money but I also learned a lot from you.

There are a couple more of these coming. GFM

another informative video, thanks for your efforts...

Been learning from you for over a decade now!

You saved me a $1000 with these videos. THANK YOU!!!

very informative ... thanks for taking the time to do this video

Thanks for the video. What is under the brass colored screw on the top right, and what does it do?

I want to convert this to LP! What spring conversion kit would i need ? TY!!

Hi Gray, I have a gas valve chain, on an old Luxaire, (SH-125). The gas valve is a Honeywell VS87A9X4X2. I replaced the limit switch about 3 years ago. I think I replaced the thermopile about 5 years ago (but I am not positive I replaced, maybe I just cleaned it). About once, or twice, a winter the main burner does not ignite - even though the pilot is on and thermostat is calling for heat. I have found that if I tap on the valve chain, it will usually ignite after a few taps. Do you think this is a thermopile issue, or gas pressure issue, or sticking gas valve issue, or something else. I replaced the limit switch about 3 years ago. I have some pictures of the gas valve train, but not sure how to post them here. The gas valve has 6 screws with wires attached - 2 screws for Thermostat (TH1 and TH2), 2 screws for thermopile/Pilot generator (RED, WHITE), and 2 screws for the limit switch (L1 and L2). I watched your videos on thermopiles, and antique furnaces. That got me to think I should put a meter on the gas valve, both while the burners are on, and after burners kick off. (I thought the millivolt readings might be useful to compare against later if it does not light again later this winter). These are what I thought I saw: 1) With the burners on: T-stat wire leads read 126 (on 200 mvDC scale) LIMIT switch leads read -4.5 (on 200 mvDC) Thermopile leads read 1 (on 200 mvDC), and 379 2000 mvDC 2) After the burners tripped off: T-stat wire leads read 1 (on 200 mvDC scale) and 611 on 2000 mvDC LIMIT switch leads read 0 (on 200 mvDC) Thermopile leads read 1 (on 200 mvDC), and 630 2000 mvDC I only changed to the 2000 mvDC setting if I saw reading of 1 on the 200 mvDC setting. Are these readings looking correct to you for a functioning gas valve? That is, am I reading it right? I ask because one of your videos showed, I think showed, 544 mvDC when you put a flame on the thermopile, and 310 mv with the pilot on it, and you stated a thermopile will trigger the valve at between 125 to 300 mv. (My readings seemed to be from 379 mv to 630 when I put the meter in the 2000 mv range). Also the autoranging meter you used displayed "0.544" - which I thing you said was 544 mV? I used a manual ranging meter, and mine showed as "379" on 2000 mV. (I hope I am getting this right?) Can you help me diagnose what I am seeing, and what might be wrong? I can send pictures of the valve if that would help. Thanks

thank you..i could not understand when I removed my wall furnace, I had no power going to it.. was making me nervous I was missing something in the wall!

great refresher its been a while since I've delt with one.

Hi Gray. I have watched many of your videos and they are great and educational. Thanks you so much for sharing your experience! I now have a problem with a new combination valve that I just installed on a milllivolt (thermopile generator) on Luxaire SH-125 gas furnace. (I replaced the valve as the main burners sometimes did not come on unless I tapped the regulator/gas valve. The old valve was a nuisance having to tap on it occasionally to open the gas valve, but it worked fine otherwise - including the pilot). The old valve was a Honeywell, with six screws in the valve body for all the leads It also had a pilot line that was fed off of a separate gas cock mounted just before the main gas cock valve. This is different from the new installed WhiteRodgers valve where the pilot line feeds out of, and is controlled by, the new combination valve. Could this be the reason the pilot goes out on high LIMIT - it is no longer indepandent of the valve control unit? The new valve seems to work fine up until the point where the limit switch is tripped and at that event the combination valve 'clunks' and main burners close - and the pilot flame goes out. So at that point the furnace is no longer operational since the pilot light is off. I had my multi meter on the two leads of the thermopile's connections at the combination valve at TH-PG and PG. The millivolts reading was 400 Mv with only the Pilot on. It drops to about 375Mv when the burners come on. When the LIMIT activates, the millivolts readings immediately drop, and the main burners and the Pilot flame both go off. (That is how I knew the pilot went out at that moment - the millivolts sudden drop and observation that pilot was out.) My new valve looks just like the on in this video. The new combination valve is actually a WhiteRodgers 36C03U, for 750 millivolt pilot generator furnaces. I have wired the limit, pilot generator and thermostat as described in the installation instructions, with the LIMIT switch leads on the power 'pigtail' of the screw in power feed, and the TH-PG terminal. The pilot generator leads are to the TH-PG, and the PG terminals, on the combination valve. The thermostat wires are to the TH, and TH-PG screws. (Not sure which is red or white at that point, as it is just two black wires in the furnace cabinet - but I assume it does not matter?) Could I have a faulty gas valve (even though it's brand new)? Have I wired something wrong? Is the Thermopile ok? (is 400 MV while connected to the combination valve) and just the PILOT FLAME adequate voltage? Do you think I need a new thermopile? I am really stumped. I can even turn the gas cock on the combination valve off, and on, several times, and the PILOT stays lit whilte the burners go off and on. The PILOT stays lit when the main burners fire up, and when the blower motor comes on. It seems wrong that the LIMIT switch should turn off the main burners and the PILOT FLAME! Should I cap the pilot outlet on the combination valve and put the pilot line back to the old, separate, pilot gas cock? Please, any help you can give me would be much appreciated. Thanks, Matt mnalep@aol.com

Great tutorial, thanks for sharing your knowledge. New subscriber

Good info, thanks

These were used on gas logs for fireplaces I seen many

Williams went to a very small generator for their wall furnaces, that gave us headaches for years. I think it only produced 180 millivolts. You could only use the length of thermostat wire that they gave you. You have to keep the T stat wire away from 120 volt wires. I had a wall furnace that would turn on every time the refrigerator ran. Caused by running the stat wire too close to the 120 volt romex supplying the refrigerator.

Thanks. More coming

that was royal RFT-50 OIL fryer.

Hey GFM! I love your videos! Can you explain how a high limit switch would be wired on these 3 terminal millivolt systems? Seems like our old 4 terminal millivolt gas valve won't keep the pilot lit. I swapped out the thermopile even though it tested good =\. The bi-metal limit switch is reading some resistance, however in hindsight, I didn't remove it completely from the system. Are limit switches normally open or closed on these millivolt systems?

Hey, great videos. I have a Hearthstone Sterling DV nat gas stove. 12 years old, don't use it much. Leave it shut down 6 months. Just started it up, had a hard time keeping pilot to stay lit. Took quite a few tries. After it finally stayed lit, I turned on T Stat remote and gas valve did not open. A few tries and it finally ignited both burners. After a minute, all went out. Same thing a few times in a row. This unit has a thermocouple and a thermopile. Which one do you think I should replace? Thanks for the help!!

very nice good video Gray

nice never see one like this before

Can anyone tell me how to connect a draft spill switch to a millivolt system?

BTW thanks for your posts

I have a White-Rogers millivolt gas valve on a gas log Model # 36C03U-333 I just installed this new gas valve the thermopile is putting out 500 millivolts I put in a new one. I have wired the thermopile to the TH-PG and PG terminals and the wall switch to the PG and TH terminals. The pilot light is strong the wall switch ohms out good. The gas valve won't open even if I jumper from PG to TH. This is the second valve I have put in thought the first one was bad but not 2 in a row. Any suggestions out there would be welcome Thanks Bill

Thanks. More good work. Have you ever taken apart a "typical" gas valve and made a video to share with us?

to install a milivolt thermostat would you connect to the same terminals as the on off switch on a gas fireplace/stove. Which terminal or terminals have the voltage present.

thanks is very informative can you explain how to replace a gas valve of fireplace?

Thanks. I'm rather simple minded so I guess it follows. GFM

I have a gas fireplace that we don't use but I know works. Right now I have a wire (low voltage) sticking out of the wall. I think it used to be a thermostat but it's been a while and I forget. Was going to just connect it to a switch, but there is no electrical box in the wall, just a wire sticking out of a hole. To use the fireplace now, I just need to connect these wires. It's long due for me to deal with this eyesore, but what do I use? Just get a thermostat or should I cut open the wall and put in a box and a switch? It's all finished drywall so I'd rather not open it up if I don't have to.

Awesome video. Hope you can help.My thermostat won’t turn on my boiler. Boiler is running but doesn’t care what thermostat says. Any ideas?

hi, i thought this gas valve is composed of a pilot valve and a main gas valve. so if the main valve solenoid is between TH and PG , then the pilot gas valve must be between Th-PG and PG? is this correct? thanks.

Great video, GRM. Thank you for your thoroughness. Can you shed any light on the types of furnace gas valves that were outlawed, the kinds with the red plastic dials? I'm going to need to be able to identify whether our cabin has one of those valves or not, in my efforts to get it working. I was told those can no longer be replaced or found.

nice work

So what terminals would you put the leads to test for voltage?

Me again, on a 2 wire valve what should the resistance reading normally be? I disconnected the thermopile/ PG and the pilot lite stays on... why? Thank you.

Help... I just bought a house with a gas fireplace (LP). I have had no luck getting it to work. The unit has no label and no one will service it without knowing the brand so I am trying to do it myself. The main gas valve does not open. I jumped the wall switch and can hear the valve click, but nothing flows through. I bought a new valve and thermopile set but it behaves the same. I have a sit 820 nova mv. It has a magnetic safety valve that I don't think is opening. So gas pressure is good, wall switch is good, thermopile and thermocouple is new, main valve is new, pilot lights but does not stay lit and gas valve does not open. No propane smell as well. I am ready to spend $1000 for a new burner and log set but I keep thinking that this should work. House inspector took 30 minutes to get it started but the flame poured out a foot high from one location. Hasn't worked since.

can you use a run a 24v style thermostat off a milivolt gas valve? your videos are very informative.

I have a royal rpt-50 oil fryer using propane. My question is does the gas valve adjust the fuel mixture?

Can you do a video to show the wiring diagram inside of gas valve? It is confused just see TH PG terminals. Also will white and red leads matter on which terminal should be connected? Thanks

Why does my natural gas fireplace vent free insert thermostat work backwards

Hi, my pilot is working just fine but when I try to turn on the flame with the light switch, it's not igniting. I called a fireplace pair company and they said I need to call an electrician. Is this an electrical problem? I want to be sure before I have an electrician come out.

what would cause a propane fireplace to burn when you are lighting the pilot.. the burner also comes on.. it should not even be able to burn until you turn the nob from the PILOT position to ON position should it? Please help. thank you

Thanks so much.!!

I was cleaning my thermopile and a shop lite that had bare wires sent110volts through the thermopile, to gas valve model#36CO3U type433 and thermostat and fried all three,which I have replaced with new parts heres the Q.my wires are not color coded and during the trouble shooting process have know idea where the go also there are only two wires I bought a Honeywell RTH2300/RTH221 thermostat with 7 connection??? help

So, where would I connect the white and red wires from the thermostat?

Question: My wife accidentally pull the TH PG wires off and I re-connect them. The problem is when I turn on the pilot successfully, the pilot turns off when I turn the heat knob to high on the thermostat. Any advise?

Are these things used in gas fireplaces and the like ? Not in gas boilers/furnaces?

Can two of the millivolt wall furnaces be controlled by one thermostat?? Is there a two pole thermostat so the signal from one furnace won't open a gas valve on another furnace that has no pilot?? Thank you

But where does the half volt come from? is it kind of a ohm thing?

Does it matter where red or white goes from thermopile to gas valve? Seen many videos and it is confusing. Is there a manufacturing spec on this?

I have a monnessen gas fire place that uses a remote controlled thermostat and would like to put a wired thermostat to it is that possible on my set up

Does this work for a deep fryer

Wondering how to wire a fireplace gas valve that does not have low voltage connections on it? Thanks

Is there a way to trigger the wall switch in the event of a power outage where the fire place has not "battery accessory"? Seems like you could use a 9 volt battery and tap the wall switch wires leading to the fireplace. Or something similar - in an emergency.

So if i have dexen 6003ks millivolt and gas fireplace without the fan, then I don’t need a power hook up? I can hear gas coming but very slowly and when i try to light i see a small spark but doesn’t light up. Is this indication of a bad or clogged valve? It hasn’t been used for a decade if ever was.

Great videos👍👍👍 What is the black wire connected to th/pg?

Question does it matter which PH wire we use . Can we switch the white and red wire without any problem ? Since they are both PG ?

What is the Millivolt volt reading when checked with a meter for a good thermo unit.

In a milivolt system, is there a thermocouple and a thermopile? Or... does the thermopile do the job of both parts?

Gray where is a good supply house to order Fireplace gas valves from and universal pilot assy?

So the red is the common dc connection? Older thermopile I’m removing from a Williams and replacing with a 700 robert Shaw valve and is giving reading of red wire being negative. My new thermopile is reading red as positive. What gives?

I searched for the next part of this series..did you post it?

How would would one turn on the gas fireplace when the pilot light is lit but only standing, in a power outage. Mine is a multi volt system as well.

I need some desperate help here please … I have an Empire GWT-35-2 with an R5245 valve system. A few days ago I started up the system again for the new season by lighting the pilot light and turning the unit on. No problems starting up however the unit will NOT shut off. It stays on and the only way to turn it off is by turning the main gas valve off. I have a brand new thermostat and a brand new thermopile(generator)…. I have no clue what could be happening. I have never had this problem with this unit in the past 14 years. Any suggestions?

Hi How do I connect a three wire thermostat wire to my gas wood stove so it powers the thermostat (nest) Thanks

i know this vid is old but for what i wanna do, i cant find anything. i would like to have a switch in my living space that turns my hot water heater up and down. its a long walk outside to the heater and it doesnt need to be on high all the time. is there a way to run a wire or something? or maybe a special thermostat or remote something or other? its a 15 year old gas unit. thanx

I just replaced the valve but when it calls for heat I hear the click but the pilot go’s out

need me some tharmoncopil do u help me???

If I have a millivolt gas valve. Do I have to use a millivolt thermostat? Or can I use a regular heat only thermostat?

Anyone can explain to me why some pilot assemblies have thermocouple only, some have thermopile only and some have both of them???? Thanks

How a gas valve works

Ty

again ,my two wires that go up to the thermostat are not color coded they are both black one is connected to the TH-GP terminal and the other is wire sent to the combination control and then back to the TH terminal so at my thermostat both wires are black and have been removed without labeling (helpful brother)which wire goes to the TH and which goes to the TH-GP terminal, you said the red is always return so that should go to the TH and the white should go to the TH-GP??? by the way my gas valve is the same as in your video... my luck has manifested in other ways as in I always pick losing lottery numbers thanks GFM

I need to know what that black wire is.

Millivolt is such a genius system, makes me wonder why we've moved away from them. Who wants to be cold when the power goes out?

What does TH stand for?

plzz help me

U forget ur high limit?😮

Why would you be eating while doing a video it's hard to understand what you say

Geez stop smacking your lips....

Don’t know what you are talking about.

Talk too much and don't get to the point

Is there a way to run the gas fireplace when the pilot is lit and the power is out? I have a switch connected to the TH and PG (above) which lights the fireplace. I was told when the power goes out I can not use the switch to turn on the fireplace.