How the Millivolt Gas Valve and 750mv Thermopile Work! Troubleshooting!

[@acservicetechchannel]

Tool List- www.amazon.com/shop/acservicetech Support- www.patreon.com/acservicetech For those that are looking for the tools used in the videos: (Linked Below) Here is a link to the Fieldpiece SC640 Multimeter- amzn.to/2x8k4Kb Here is a link to the Fieldpiece SC660 Wireless Multimeter- amzn.to/2gWDUhc Here is the link for the Robertshaw low profile millivolt gas valve- amzn.to/2iLXzEh Here is the link for the White Rodgers 750mv thermopile- amzn.to/2zhKVnF Here is the link for the Robertshaw Pilot and 750mv Thermopile combo- amzn.to/2zZAH8w Here is the link for the Honeywell armored cable 750mv Thermopile- amzn.to/2yfR9UK Here is the link for the Irwin Wire Stripper/Cutter/Crimper- amzn.to/2dGTj2V Here is a link to the Stanley 6 in 1 screwdriver- amzn.to/2x7NuaZ Here is a link to the thermostat 3/32 screwdriver - amzn.to/2hxt7uK Here is a link to the Pro 3000 24v Thermostat used in the video- amzn.to/2keuUbs Other tool links can be found in the video description section. ACSERVICETECH is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon. All of the ACSERVICETECH Playlists- kzbin.info/door/OZR-1IqsAer9wzlvFgb4mAplaylists?view_as=public If you want to support the ACSERVICETECH Channel and receive more HVAC content, check out www.Patreon.com/acservicetech

[@pxtuber]

What by no

[@fartsunltd6981]

Thank you. I do supermarket refrigeration and got my lunch ate by telling my brother that I could fix his 30 year old fireplace. I was generating 350mv on the pilot and didnt know what it took to energize the solenoid. 8 months later this video made me a hero. Thank you.

[@acservicetechchannel]

Ha ha, thanks for letting me know that you appreciated the video Michael!

[@Drummer4G0D]

This video is 100% the best in depth coverage of millivolt gas valves I’ve found. You answered questions i didn’t even know i had. Thank you so much. These have been a pain in my ass

[@acservicetechchannel]

Thank you very much and awesome channel name!

[@cdnlong1]

Very helpful, educational video! You get straight to the fundamentals of the operation. I just fixed my gas fireplace thanks to your help! An additional tip. Don't know if you would endorse it or not.... You can use a 1.5v AAA battery to test the operation of either of the solenoids, if you you suspect the power from the thermopile is insufficient.

[@cmiltimore470]

Thanks for an excellent video. I put 3 different thermostats on a wall heater, each of them worked, on an intermittent basis. Your video explained it, too much resistance for the small voltage to overcome. Bought a millivolt only thermostat at Home Dept, and believe that will fix the problem. Thanks again, I was freaking out when I thought I had gotten ahold of 3 faulty units.

[@AAA-0]

Thank you. Very informative. I have a friend whose ventless natural gas fireplace will work for about 30” and then shuts down. This gives me a good place to start. I am grateful to you and KZbin for these in-depth troubleshooting guides.

[@tedlahm5740]

Sir: Believe you have your finger pointing to the wrong terminal when describing the operation of COMMON TERMINAL and the other two terminals primary and secondary gas valve operation. EXCELLENT VIDEO. Clear concise information. Thank you

[@johnguerrero4305]

The absolute, most precise explanation of the millivolt gas valve.

[@anthonynavarromartinez1051]

I HAVE BIENG OUT OF THE SERVICE FIELD FOR OVER 12 YEARS. AND NEEDED A CRASH COURSE ON MILIVOLT SYSTEM ON A CALL I DID FOR A FREIND. THANKS FOR YOUR VIDEO VERY HELPFUL. KNOW I CAN COMPLETE WORK. THANKS

[@acservicetechchannel]

Glad to help!

[@edelmanhomes]

This was very helpful in diagnosing and repairing an older gas fireplace. Tested and saw there was not enough voltage, so we adjusted the pilot and now everything is working!

[@ericedelman]

@@goldstarhvacrllc2567 This was a while ago. As I recall, there was a screw I had to turn to increase the gas flow to the pilot.

[@zaeet65]

Thank you so much your video just saved my day I was in the middle of winter cold day with 50° Fahrenheit in my house and I got two person coming in my house and giving up on this job and I took it to myself and watch the video your video and I got it to work so thank you so much best of luck

[@acservicetechchannel]

Thanks Zamil!

[@Ceja818]

Thank you I just fixed my heater with this video! Glad I didn't have to pay someone to come lol

[@PFBzzz]

EXCELLENT VIDEO! So many youtube video's drone on and on (and on) with irrelevant info, but this one quickly gave me the EXACT the information I needed to troubleshoot my milivolt gas fireplace valve. Thanks!

[@acservicetechchannel]

Thanks PFBzzz!

[@AnthonyTalerico]

What an amazing video. You just helped me to understand everything I need to know and why my gas fireplace no longer stays lit. Thank you!

[@patriot-dv6dh]

Excellent explanation of the millivolt valve, in less than 10 mins! My pilot works, but the main flame doesn't. Will troubleshoot tonight. Thanks!

[@randallprue4134]

This short video clearly explains and shows the main events and components in my millivolt gravity-feed propane furnace (a Hunter). Thank you for that!

[@mattn6936]

I'm a refrigeration Journeyman so don't work too much on Gas heaters. Thought I'd be a nice guy and change a valve in a Vermont stove for a friend. I could not figure out how the valve was supposed to work without a 24V supply - lol. This video just answered all my questions. Thanks for posting.

[@acservicetechchannel]

Thanks Matt N!

[@billybbob18]

I work on gas stuff all the time, and it still amazes me how little current is required to run the system. Use an old mechanical thermostat and you don't even need batteries.

[@workingshlub8861]

@@billybbob18 i still have a 1970s boiler in one of my rentals that is milivolt system still going strong...it is 120 volt for circulator but burner controls are milivolt...

[@jimbola77]

very very excellent presentation!!!! thank you for taking your time to share your excellent knowledge I love watching and taking note's off your work.

[@acservicetechchannel]

Thanks Jimbola77!

[@josevilla3255]

Very helpful videos Thank you for sharing this video it really helped me to adjust flame pilot I always watched your videos Thank you very much

[@Keo0oo]

This guy is very smart and detailed. Very clear in explanation. GREAT JOB!

[@acservicetechchannel]

Thanks Keo!

[@AMGmechanic]

Thank you for this video. That was a very good explanation of how the system works.

[@acservicetechchannel]

Glad you enjoyed it!

[@alexanderc05]

I need to replace my old sticking gas valve, just by chance in this sample it is my same old Robertshaw valve, also need to add a thermostat like in the sample, thank you very much it is very helpful, explanation is very clear.

[@acservicetechchannel]

Make sure the thermostat is rated to work with MV and not just 24v, thanks!

[@738polarbear]

Excellent video tutorial . Exceedingly clear

[@adranserrano312]

Thank you brother your the best teacher ever you rock🤘🏾

[@esbigerodeo1]

Great video,ive installed and rebuilt so many millivolt systems ( floor furnaces,wall heaters,etc.) in my early days. The most basic and best backup heating around.

[@acservicetechchannel]

Thanks Evan, yes simple is certainly reliable. I think now we are too far in the efficiency game that pieces eventually break much much more compared to those older systems you are referring to, thanks and Merry Christmas!

[@billthompson9595]

Hi! Am i ever glad i have subscribed to your channel..You have excellent tutorials. THANK YOU VERY MUCH

[@acservicetechchannel]

Awesome, thank you!

[@nurfetalic205]

Craig you are the Magic Man. Excellent video. Best regards from my electrical engineering students.

[@acservicetechchannel]

Glad to help Nurfet Alic!

[@rico700hd]

Awesome, no nonsense video. Thanks!

[@DanV-ls3jf]

Great Video Craig!!

[@jaymz0074]

Awesome video. Thank you for your time in doing all your videos.

[@acservicetechchannel]

Thanks James!

[@theo9976]

Great educational video. Thank you for posting.

[@jackpast]

Real nice video and explanation, Craig. Great work!

[@acservicetechchannel]

Thanks Jack!

[@tkmair6559]

Have a 1960s Camper with nice old Coleman propane millivolt wall heater. I did something, I hope is not terrible, but I attached a AA battery to my valve leads. It was like jump starting the solenoid. I heard the solenoid chirp open. Took off the battery and it continued to throw flame. Had heat, looked great. But I have never been able to get the unit to work again since then. Having problems getting the pilot to stay on. I replaced the thermopile and pilot unit with new one after finding a lot of rust inside the pilot chamber, also replaced the Tstat with something very simple (no battery). I think the gas control valve has faulty solenoid and even the knob is very hard to turn. So I may buy a new valve controller now that I know they are still being made! After watching your video, will try yet another time to take some multimeter measurements before getting a new valve. Could be the pilot flow adjuster is turned too low, or pilot needs to be pointed down more, but really I think it needs new control. Thank you!

[@billybbob18]

That AA battery is 1.6 volts at full charge. That's 8x what the coil needs to operate. Time for a new valve my friend. It's expensive compared to a thermopile.

[@MJ-iy4fb]

Nice video, and a need setup, thanks for posting.

[@demoking1422]

Great video well explained I suspect maybe I need to clean the thermopile , if that does not work I will watch the video again lol Thanks !

[@acservicetechchannel]

If you want to support the ACSERVICETECH Channel and receive more HVAC content, check out www.Patreon.com/acservicetech All of the ACSERVICETECH Playlists- kzbin.info/door/OZR-1IqsAer9wzlvFgb4mAplaylists?view_as=public

[@MR-nl8xr]

acservicetech. if you we make donation is it equall to purchasing your vids. in other words, can we download videos.

[@acservicetechchannel]

Hey Max R, I do sell rights to the videos if you were interested in using a video as a teaching resource off of youtube. I am not planning on pulling them off of youtube so you should have access to them. Patreon is a way to sponsor new videos uploaded to KZbin as well as for the articles and other videos posted there. Exactly what were you looking for?

[@robertaaime2121]

Great video, well presented, thanks

[@GarysBBQSupplies]

That was well explained. Thank you.

[@whitesheatingairappliancer7101]

Thank you, very educational. Thank you Ron White

[@acservicetechchannel]

Thanks Ron!

[@jp040759]

I was always unsure if the thermocouple and thermopile had enough power to drive the pilot and main gas valves. THANX.

[@azaquihelify]

perfect presentation, thank you sooo much!!!

[@tedlahm5740]

Very informative. thanks

[@acservicetechchannel]

Glad it was helpful!

[@jimbola77]

thank you ken for sharing! God Bless Brother.

[@lancerudy9934]

Always good videos

[@techvlad8736]

Working on a gas fireplace this helps a lot. I read only 55mv at the most. I decided to replace the pilot assembly that comes with the themopile and sparker. Because the cleaning didn't work for me

[@bubba1984]

Thank you, very informative! Would you be kind as to answer a viewer's question: do thermocouples go bad over time meaning produce less energy? Mine shows open circuit 325mV and pilot-only 264mV and main-valve-on 154mV, I'm seeing intermittent on/off issues and I suspect my thermocouple just isn't producing enough power any longer but wanted to get your input before assuming anything as to probable cause? Thank you

[@mostlikelywedoitservices6926]

Yes they do go bad. The difference on thermal bulb and thermopile is that the thermopile has several generators inside of it and thats how it produces the higher MV output compared to a single thermal bulb generator.

[@voidisyinyangvoidisyinyang885]

@@mostlikelywedoitservices6926 Yes we're getting the thermocouple replaced - and the technician turned off the pilot flame before he left!! So now the direct vent is kicking in cold air. haha. Dang! thanks for explaining this problem. I'll call them back today to see if they got the new thermocouple yet.

[@bryanp8010]

For a Robert Shaw 710-502 or dexen 6003 they generally wont operate prior to 325mv. I will say, pilot flame is usually something you dont want to adjust. It’s common to get leaks there. Pilot flame is set pretty solid from the factory. Dexen Tpile only valves tend to have sticking magnet issues also. The 6003 is a garbage valve.

[@brianost2703]

Could I swap out my gas valve with a thermocouple and thermopile and just use 1 thermopile setup and get rid of the thermocouple? This is on my old Heat n Glo SL550TRSLP-C

[@phillipjoy1305]

Great videos 😊

[@dadsadvice5951]

Excellent information. Do you know what the smallest millivolt gas valve might be? I'm interested in building a tiny propane furnace and would like to find the most miniature gas valve that doesn't require power. Thanks.

[@Richism4U]

Thank You for putting out this video...made a difference for me

[@acservicetechchannel]

Awesome, thanks Richism4U!

[@mwrbernard]

Thank you for the excellent video explanation. I have had occasional problems with my natural gas fireplace failing to open the gas valve on command from the thermostat. I have a trusted gas technician coming in today to have a look at the thermopile/valve device on the fireplace. During your video however, you don't make reference to the possibility that this unit may simply require replacement after many years of service (about 20 in our case.) BTW, we have already replaced the new Honeywell thermostat and the problem continues to occur, So the two final steps are to inspect the onboard gas valve and thermopile and to inspect the wiring between the two.

[@workingshlub8861]

im sure you have your issue fixed by now but i had the same issue and it turns out the internal magnet for the gas valve would occassionaly get stuck shut ....no flow to main burner.. few taps with a screwdriver and it was fixed..

[@jayhdez2329]

@@workingshlub8861 what was the symptom? When I call for heat at the thermostat I hear a click and the pilot turns off instead of opening the valve. Where do you tap it? Thanks

[@workingshlub8861]

@@jayhdez2329 if the pilot wont stay on at all you probably have a weak thermopile.....click at the valve or the thermostat??

[@jayhdez2329]

@@workingshlub8861 the pilot stays on. It’s when I move the thermostat to call for heat when I hear a click and instead of igniting the burners, the pilot then shuts off

[@workingshlub8861]

do you have a thermopile or a thermocouple setup?? are there wires going to the gas valve??

[@olegs79]

So HVAC guys are like little electricians. Nice video.

[@Swxnflu]

Lol I would have still said “woah” even knowing that without being connected to burners it would do that. 😂 Great information! Thank you!

[@geojor]

great for any DIYer, thanks ...

[@Albisriede]

Nice info. I'm possibly getting closer to understanding how my old Empire direct vent heater works, or to be more specific, why it may not work properly. It's installed at a remote location and is used only occasionally. The pilot light works, but the remote (with a Mercury filled switch) no longer influences the shut off. The heater runs full blast regardless, even when the remote is completely disconnected - unless the knob by the heater is turned back to 'Pilot only'. Maybe it's time for a new heater, after all, the thing has worked flawlessly for 30 years.

[@drummergrl1000]

Aid you get it working? I have an old Empire too.

[@jfarinacci0329]

Really good content. Thank you.

[@acservicetechchannel]

I appreciate that!

[@fernandomartins7261]

Many thanks and congratulations on a video well and thoroughly explained

[@acservicetechchannel]

Thanks Fernando!

[@mostlikelywedoitservices6926]

rule of thumb. Voltage drop will be near half the of the total millivolt reading before energizing main gas valve.

[@barkster]

Great video, I have a heatilator fireplace that has thermocouple and thermopile. Replaced both but when I light pilot it will light and stays on for a bit but goes off. When I measure thermopile it won't go up to 105mv but if I disconnect it from valve will go up to 350mv or so. Any suggestions

[@m.n.3490]

Great video. I am trouble shooting a millivolt White Rodgers 36C03U gas valve (replaced in 2015). I noticed it is wired differently than in your video. First, my pilot gen screw is labled PG (PILOT GENERATOR) versus yours which is labled TP (THERMOPILE) Now, One of my tsat wire wires first goes to the HIGH LIMIT SWITCH (HLS), and then the 2nd wire from the HLS goes to the TH/PG screw. Yours has no HLS. (The HLS had to be wired like this to prevent the pilot valve from being shut when the HLS shut off the main valve). In your video the 2nd tsat wire goes directly to the TP screw. In other words your tsat wires go to the TP screw and the TH screw - but my tsat wires go to the TH screw and the TH/PG screw (with the HLS in the middle). It's been working fine all winter, and for a few years, but is now acting up and not firing up all the time. I tried a new thermostat 'brain' part, which by itself did not improve things. Then I cleaned the pilot generator with steel wool last night, and the main burner came on 3 times without a problem. But I don't know if I've solved the issue? (I did note that the mv across PG and TH/PG went from around 400mv, to around 500mv, after I cleaned the thermopile, which I thought was a meaningful increase). I am still trying to diagnose any possible issues... I have a service sheet from a previous millivolt gas valve (a Robert Shaw 1995) that says to check system resistance between TH/TP and TH with tsat closed and calling for heat I think it is telling me it should be less than 80mv. Mine is about 140mv. This is after I put the new tsat face on. (BTW, I left the old tsat base in place mounted on the wall, as it just has the wires in it, and the screws were tight, and all the 'brains/electronics were in the 'front/face' part of the new tsat I bought - which was the same exact model as the old tstat. Is that 140mv resistance an issue that might be preventing the main valve from opening? I also notice a bit of melted wire in the tstat wires where it was resting against a burner. Could that causing the140mv resistance? Or is the resistance from the HLS being wired into the one tstat wires path? I did notice that during one of the main valve opening cycles that only the two middle burners flamed on (instead of all 5) and then quickly went out (in about 2 seconds). I thought this was due to the main valve opening partially but not all the way, and not staying open for more than a second or two. I am hoping that cleaning the THERMOPILE and then seeing that 100+ MV increase will resolve my main valve opening issue? It seems to have for at lesst 4 cycles I observed. Sie I am not 100% confident with this millivolt system, I thought I'd ask some of the questions above, after I saw your excellent troubleshooting video, and seeing your knowledge on these millivolt gas valves. Can you offer any helpful advice? Oh, one more thing, I noticed before I cleaned the thermopile, that I was able to get the main valve to open by placing a jumper wire across the TH and the TH/PG screws. This makes me think I do not have a bad gas valve, but more likely a voltage issue? What to you think?

[@acservicetechchannel]

If the wires have 140mv through with the thermostat closed, that is a bit high. Make sure the thermostat is rated for 750mv even though it is a direct replacement of the old one and maybe run new thermostat wire or at least run some new as far as you can, thanks!

[@m.n.3490]

@@acservicetechchannel Thanks for the reply. It has been two nights now, and the furnace is working still. I am thinking that cleaning the thermopile, and getting the extra 125 Mv - to around 525 (tstat open) - may have been the resolution. Do you think the bump from around 400Mv prior to cleaning it, to the 525Mv after cleaning it would make a big difference regarding the main valve opening? I also noticed that prior to cleaning the thermopile, that I could also get the main valve to open by tapping with a screwdriver on the side of the gas valve. I took that as an indication that perhaps the valve was not getting enough voltage to open? I noticed that resistance from TH to TH/PG (tstat closed) is now around 190, so it went up after cleaning also. Does that seem right? I was thinking about cutting out the two inches of tstat wiring that were singed, and just resplice them back with some wire nuts - to see if the resistance drops. Is that a good idea? The tsat is on the second floor of a two story home. I do not think running new wires would be easy, at all. I am thinking of just leaving it all 'as is' for now as long as it keeps working. Although I was thinking if the increased voltage fixed the valve issue, that maybe a new thermopile is in order.

[@acservicetechchannel]

I am just saying run new wire from where after it comes down from the 2nd floor in the basement up to the gas valve, this way, that is all new. Thats great things have been working, thanks!

[@m.n.3490]

@@acservicetechchannel I've never replaced tstat wiring. How would I do that? Put a weight on the new wire and drop it down the wall? Or would I need to attach new wire to old wire and pull it through? (I am worried about the consequences if I cannot get the new wire in place). Do you think the main valve opening issue is related to the resistance, and not the thermopile output?

[@RODRIGUEZ13005]

Thanks for that great video

[@acservicetechchannel]

Thanks Julio!

[@SDeanP]

Excellent video and information, thank you!

[@acservicetechchannel]

Thanks Stanley!

[@u8915055]

What a fantastic video! I learned a lot. I have a regency natural gas fireplace that will light the pilot fine and even support the lower smaller burner to run fine. But as soon as I turn on the main burner I maybe get 5 mins and the whole thing shuts down. Tell me if you don’t mind, what happens if things are running and the thermopile voltage drops. Will it just kick off the main gas valve or will everything go out, burners and pilot light? I didn’t catch that if it was in the video. Thank you

[@drummergrl1000]

same question, did you get it figured out?

[@m.n.3490]

Great video.

[@acservicetechchannel]

Thanks Matt!

[@Orrphan]

Great vid, I think I just heard you clarify but want to pose this to you. . So you’ve got the white wire going to tp terminal. I’m Installing robertshaw 700 valve to Williams furnace and old thermopile red wire is negative and new thermopile I’m using the red wire is positive. What’s going on?

[@timborocksloud]

an absolutely outstanding video. I have a gas fireplace where the pilot light lights fine, good flame, when I push in the black knob as seen in the video above. However, once I release and before I can rotate knob from "pilot" position to "on" position the pilot extinguishes. I had a tech come out and look at it and he has quoted me $750 parts and labor for the repair, but I think I can replace this entire assembly for a fraction of that cost, yes?

[@acservicetechchannel]

I would always recommend a tech to do the work, thanks

[@JPHolling]

Im currently getting a reading of 550mV between TP and THTP. I know you said 600mV. Main burner is not turning on. Does this most likely mean theres an issue with the main gas valve? Burner does not turn on when I jump using a paperclip between TP and TH.

[@KBS117]

When I push the knob in to light the pilot, I get gas out of the main burner. I can light the burner without lighting the pilot light. Once the thermocouple heats up, it will stay lit. If I turn the gas pressure down and thermocouple cools down it will shut off all gas. Never had that happen on any gas valve anywhere. Any clue?

[@truthmatters-t7e]

TP is thermopile and TH is thermostat. There is no solenoid... it is a spring loaded safety magnet in that Robertshaw valve. The pilot flame was horrendous.

[@throttlebottle5906]

I used to light them with a torch for "quick" heating, watch voltage both open and thermostat calling, if they didn't spike up with torch instantly, BAD

[@MR-nl8xr]

throttle bottle. oooh, i like that one.

[@mark.r8900]

Do you have to check manifold gas pressure if replacing one? Where is the port to hook up manometer and adjustment screw? Thanks

[@youtubedjdj]

My heatilator GNDC36 does not have the black ground wire on it as yours does on the top. Could that be why my pilot light works perfect, but the burner will not ignite?

[@scottt2325]

thanks so much .. you just saved me a couple hundred bucks .. a few hours of bitchin' .. and probably a cut knuckle or two

[@altk3646]

Thanks for the info. Can you tell me if this can support a C-wire ?

[@gyver471]

I thought the the common is where the solenoid wire is connected to. Can you explain do I have it wrong?

[@Tacoslate]

I was hoping you could answer a question for me. I replaced my thermopile(it was only reading 190mV) and I got the new one in, great, reading about 520mV when pilot is on. When I jump the leads or turn the on switch on(no thermostat for the fireplace, just on and off) the flame kicks on, but only at about half of what it should be? And the thermopile reads 180mV and same with the pilot. So the question is, why am I getting such a large voltage drop? And is that why the valve isn’t functioning properly?

[@lonetraveler5660]

Does the polarity of thermopile matter?

[@mark.r8900]

Hi, if you put your probes across th/tp and th would you have 0v all the time? Thanks

[@joejustus3169]

Hello. I have a Empire DV35 natural gas wall heater with a millivolt system. I have had a regular 24 volt thermostat for years without a problem. Recently I can’t get the main burner to come on. I have replaced the gas valve but still not coming on. Pilot stays lit. Any thoughts? Thanks.

[@donburnside6448]

Hello thanks for this video. I have an empire DV210 wall heater in a workshop. The unit is 4 years old only used in the cold weather so about 6 months out of a year. My furnace tech has changed the thermopile 4 times since installation. He has many other heaters in service and some for 10 to 15 years and never required service. He is at a loss as to why the thermopile keeps failing. Any ideas?

[@drummergrl1000]

did you figure this out yet? would love to know .

[@donburnside6448]

@@drummergrl1000 yes the pilot was set to low. After turning the pilot flame higher the heater is working great

[@emiliomigliozzi294]

I can't tell why the flames in my fireplace are so low and all blue about 1unch high. Years before they would be yellow and blue about 8 inches high. Now I closed the physical entrance where we turn a nob to increase the gas input but nothing happens. I check the thermopile, at rest and it reads 560millvolts with the pilot on, when I open the thermostat it goes down to 190 to 235 is this enough to open the gas valve. Should I assume the thermopile is defective.

[@euro9115]

Thank you for the very informative/direct and to the point presentation.I never knew how my old Coleman floor furnace worked until watching your video. Now for the hard part. I would like to add a small 120 vac fan to direct some of the heat into another area of the house but only want the fan to run when the burners are active. Is there any way to do this with a millivolt system? If not, can I just replace the millivolt valve with a 24 vac valve, 24 vac transformer, and add a 24 vac (coil) relay to control the 120 vac fan? I already have a modern thermostat that has a fan control switch (auto/manual).

[@acservicetechchannel]

You can't add to the 750mv system. It is not too simple to change all of that over, thanks

[@susanhenderson2322]

My thermopile will only make .350v from pilot, it drops to .200v when gas valve commanded on by thermostat, after approximately 15 min that voltage starts to drop untill under .100 v at which time the valve closes due to insufficient voltage, this is a brand new theropile, could the valve be drawing to much voltage or could the pile be faulty,

[@kutaibadawod7400]

Hi, any chance of having the resistances of the 4 different operators, 24Vac, 120Vac, 240Vac and millivolt. regards

[@matthewkleinmann]

I don't think there is a user adjustable pilot adjustment on the gas valves on vent free type heaters as the oxygen depletion safety system depends on the pilot being weak and going out if the oxygen level in the air goes below some critical level. I have also heard they make the pilot jets out of a sintered material that are designed to fall apart if you try to ream them out to clean them. If your pilot level is low in a vent free heater, use compressed air to blow it clean but don't try and ream it out. It was cool seeing the thermopile values as the valve cycled.

[@acservicetechchannel]

Some heaters do not have a pilot adjustment but many combination or millivolt systems do. It is possibe that more ventless do not have adjustments but I am mainly working on home, trailer, and commercial heaters, thanks

[@John-lj6qr]

The middle one is TP and the top one is TP TH

[@derekwhite4628]

I noticed that the robertshaw valve shows the jumper to the thermocouple port (from the thermopile connection) for millivolt set up. Is the required or can you operate with a thermopile and a thermocouple without the jumper?

[@lengnuan913]

The upper terminal is TP/TH, not TP. The middle terminal is TP, not TP/TH. Also I suspect the thermostat pro 3000 is rated for millivolt, but pro 1000 is rated for millivolt.

[@adriancontreras1880]

I'm trying to pass this test so I can get into my companies oven training course. It's asking me what voltage I would expect to see when testing a thermopile. According to my research it's supposed to be around 750 millivolts DC but the damn answer key only gives me 50, 900,125 or 500 millivolts dc. I'm so confused!!

[@ptbronco03]

Question...What if the valve is not closing? The boiler temp is set to 170, the boiler keeps heating to higher, I tap the valve and it stops firing. Federal Taco Zone Controller SR1502 Aquastat Brand: Resideo SKU: L8148J1009 gas valve VS8279A10342 1/2 X 3/4 INT JD4

[@tonys4751]

I have a gravity furnace and the voltage at the thermostat leads is 390mv with just pilot heat. Sometimes the heater does not turn on using a Honeywell thermostat. If I jump the red and white wires, it fires up 100% of the time. Do I have a faulty thermostat?

[@acservicetechchannel]

Yeah, the resistance across the thermostat is too much but also, the mv seems a little low. Try reading the resistance value across the terminals of the thermostat when calling for heat. It should be very close to 0.0ohms, thanks

[@tonys4751]

AC Service Tech LLC , I have done that and it’s not always dropping to zero. Sadly, I seem to run into this problem with Honey thermostats - which dominate the market. They work well for a week and then get flakey on me. Can you recommend another brand and model for 750mv? Thanks so much!

[@workingshlub8861]

i realize this is 2 years old but i had the same issue ....turns out the gas valve was getting stuck shut now and then...i had pilot flame but no main burner...drove me crazy for months.. few light taps with a screwdriver handle and disconnecting the gas line and getting all the crap out of it fixed it...dirt can clog up the valves..rare but happens..

[@m.n.3490]

I am having trouble with main gas valve opening. I have tried a few different thermopiles. They work fir a few days, or few weeks, then stop opening main valve. I clean it up and starts working again. Can I try increasing the pilot by turning the adjusting screw (counterclockwise?)? Could I put a 2nd thermopile, placed along aside the installed one, to get more volts into gas valve help? Or could that harm the valve?

[@jwill9877]

My gas valve does all this and still doesn't light. I even hear a single click sound when I put a jumper over the switch. Could this mean a gas supply problem?

[@2manycatsforadime]

what if you have around 450Mv but the gas valve opens intermittent or closes prematurely. Furnace is not lighting but the thermostat contacts have to be manually open, closed, open closed etc till the furnace starts. Or I can just twist or jumper the two wires and the furnace lights. Wires have continuity and I have changed thermostats. Only thing I can think of is the gas valve is failing and 450Mv is not quite enough now or the valve is sticky and will only open when the Mv is applied on off on off on off untill it makes it jump open.

[@henryodogwu6604]

what would be the problem if 24v is registered when wires are unplugged from the gas valve, but the voltage drops when wires are connected to the gas valve?

[@kyleperry1701]

I was working on a floor furnace yesterday and was so confused lol

[@iviaverick52]

just to clarify, because it hasn't been completely clear in the videos I've tried watching, these millivolt valves don't need to be wired into mains voltage to function, just a switch to directly complete the valve circuit (if you don't go with a thermostat option). Is that right?

[@acservicetechchannel]

Yes correct on the 750 millivolt gas valve units

[@EurekaRecycler]

why do some also have a thermocouple ( are these kind with a thermocouple the same type of thermocouple found in a water heater ? Thank you

[@acservicetechchannel]

The thermopile is 750mv and controls the pilot and the main. A 30mv thermocouple can only control the pilot, thanks

[@martelproductions1975]

New Empire DV heater. Thermostat is closed, but i need to tap gas valve to get it to "kick in." Ideas? Also, anyone suggest an inexpensive device to measure the electrical energy? Won't use it much. Many thanks.