This is getting educational.

So I installed that new thermopile in the bedroom heater, right? And it fixed nothing. I didn’t even know what it did: Thought I did but I was not right about that. So it’s supposed to produce current and … power the gas valve?

Anyway, apparently the spec is 500mv but this one – brand new, remember – is producing less than 400. Tops out at 392. Significant? I dunno. I took somebody’s advice and put the question to a furnace forum.

ETA: Somebody on that forum suggested I measure the voltage with the thermostat turned on, and it’s substantially lower. Starts at 187mv and slowly drops. I don’t know what that means.

About Joel

You shouldn't ask these questions of a paranoid recluse, you know.
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12 Responses to This is getting educational.

  1. Anonymous says:

    Terrapod the retired EE here. I think the thermopile as described takes heat from the pilot flame to generate electricity. If the spec says 500 mV that is quite a bit but not the amperage, that would not be enough to trigger a gas valve so any circuit that has to power a solenoid needs a good size honking capacitor to store that energy and kick the solenoid valve when demand is made to turn on the heat.

    So, since I don’t have a diagram or model number to research, I would look at the board that has electronics on it and see if there are any large capacitors on it, likely electrolytic type in higher micro farad range. Electrolytic capacitors fail, I have been repairing old radios for many years and invariably have to replace them, same with my motor start capacitors on the furnace/AC, they fail regularly.

    If you send me the model number and maker of the unit I can do some real research as all of the above is just noodling a SWAG that might be pointing in the right direction.

  2. Ben says:

    Don’t know which model is yours, but I read a random manual from your manufacturer’s site, and there was information about measuring milivolts. I would guess that in-use milivolts would be something less than open-circuit milivolts. So your measurement doesn’t surprise me, but I’m not speaking from any specific experience.

  3. Anonymous says:

    Terrapod again.

    /ETA: Somebody on that forum suggested I measure the voltage with the thermostat turned on, and it’s substantially lower. Starts at 187mv and slowly drops. I don’t know what that means./

    I missed this before. What you are describing is the voltage across a capacitor that is slowly dropping as it discharges into your multimeter which has a high input impedance but still enough to drain a capacitor.

    Post the model/make and I will look at issue it in detail. I am sure it is not a complicated device but need to see the schematic.

    Talley ho

  4. hightecrebel says:

    Hey Joel, I work on these things for a living, you up for posting a pic (or even better a video) of how the flame hits the thermopile? If not, can you show a pic of the gas valve and the model/serial on that plate in the bottom of the heater?

  5. Anonymous says:

    Why not post the schematic diagram? Not much to a space heater.

    You seem intent on dragging this out by posting small tidbits of information.

  6. hightecrebel says:


    Is that to me or Joel? If Joel, he may not HAVE the schematic diagram. If to me, I don’t know which heater he has, so I can’t post one. And there really isn’t much to it. Pilot heats thermopile (possibly also a thermocouple), thermopile/thermocouple generates enough millivoltage to hold the pilot solenoid open, and when the switch or millivolt thermostat calls for heat (closes), it opens the main solenoid and sends gas through.

    Honestly, assuming the switch/thermostat is good (I’ve seen ONE go bad in the last six years) it sounds like either the pilot is clogged up enough it’s not hitting the thermopile properly, which would decrease the energy generation, or the solenoid in the valve has gone bad, meaning the valve itself needs to be replaced. Of those, the pilot being clogged is more likely.

  7. Anonymous says:

    Anon @ 5:02,
    You seem intent on being a Dick.
    Sorry Joel, had to be said.
    Eric. 🙂
    No flame wars, I wont play, Anon.

  8. Anonymous says:

    “If you send me the model number and maker of the unit” Terrapod..
    Yes, the make (Empire?) and model number to maybe obtain a good schematic is almost essential here. There is some considerable talent here trying to meet this challenge, but we need a ‘roadmap’. There must be a ID plate somewhere on the unit, or maybe a good photo of the assembled front of the unit could give a clue. There’s lots of photos in the search engines of Empire heaters with model numbers.

    By the way, are you using a millivolt rated thermostat on the system?


  9. Anonymous says:

    Anon @ 5:02, the problem with self-education is that you don’t know what questions need to be asked.

  10. Anonymous says:

    I agree with hightecrebel: I’ve had similar problems with stoves where the flame wasn’t aimed right.

  11. Anonymous says:

    Based on an older post it sounds like an Empire DV210 ( And I agree, between the collective minds of the folks who read/comment here we should be able to get this fixed!

  12. OK, dumb question/silly idea time. Given how much “fun” you’ve had with this thing, would you consider replacing it? The vanlife crowd is in love with the “Chinese diesel heater” (representative member They do use electricity, so that would have implications for your solar system.

    Your loyal readership who are living vicariously through you might be willing to subsidize the materials. I would chip in.

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