What Is A 250-750 mv Thermopile?

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ajaynejr

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I am looking at a thermopile (a cigarette shaped/sized item similar to a thermocouple) rated at "250-750 millivolts" output. Could someone explain the meaning of 250-750 mv versus 250 mv output by itself or 750 mv output by itself? The heater I want to install it in does not work with its old thermopile I measured at (a supposedly age degraded) 360 mv output. Will a new 250-750 mv thermopile work?

The catalog listing is for a single item. Not a choice of thermopiles, one for 250 mv, one for 750 mv, etc. I was about to choose this one because delivery date was sooner.

Boiler versus furnace vs water heater is not relevant here. The thermopile (or thermocouple) works the same way and does the same thing for any of these heaters, gas models.
 
The output voltage may vary with the load but for a range this wide they should tell you what load you should use. Sounds like a kind of a universal replacement.

BTW, you can simulate this device with any AA battery & two resistors.
 
I dug into these circuits a long time ago.
IIRC, a 760 mV TP when connected to the valve may drop to half that value, about 380 mV.
With a valve coil resistance of 30 ohms, the current in this series circuit may be about 12 mA.
The posted values & actual values will probably be in the ballpark of these design values.
 
Thanks.

Ultimately I got a replacement thermopile with a straight 750 my rating.

The new thermopile showed under-load voltages greater than the old one did, so I am assuming for now that the problem (random loss of the standing pilot) has been cured.




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The new thermopile showed under-load voltages greater than the old one did, so I am assuming for now that the problem (random loss of the standing pilot) has been cured.
It could be.
The higher voltage will put more power into the valve solenoid but I can't imagine this shortening the valve life significantly.

Somebody else here had a pilot that went out very infrequently. I think they put a cap on the stack.
 
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