# Thermcouper



## jabpp4 (Sep 3, 2012)

How often should a thermocoupler be replace on a hot,water tank?  We have replaced ours about 4-5 times in 4 yrs. Is something wrong? Our house is new, 4 yrs old.


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## kok328 (Sep 4, 2012)

Not sure what the problem could be but, 4-5 times in 4 yrs is excessive


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## Blue Jay (Sep 4, 2012)

Possible the pilot may be too high and burning it up?


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## notmrjohn (Oct 17, 2012)

If only 4 years old, your thermocouple probably has a diode attached to it, that may be part that is actually being damaged.
. Not enough air flowing through the combustion chamber to carry the heat up through the flue causes heat build up, which kills the thermocouple.   Make sure exhaust flue is large enough, not leaking, unobstructed inside, and runs in as straight and short route thru roof as possible and extends above roof far enough.  Also make sure plenty of air is getting to unit to increase air flow, could be plenty of air to keep it burning but not enough to keep thermocouple cool. Larger or another opening into heater compartment, opening should be as low as possible.

Have all  your replacements been same brand? Another brand may be more rugged and dependable.


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## Wuzzat? (Oct 17, 2012)

Sounds like they are being severely abused by some as yet unfound root cause.

Measure the voltage output of your thermocouples to check what temps. they are seeing.  Common voltages are 25 mV up to 750 mV and when they are turning on a gas valve the voltages may drop to half.  

also check the current flow. (Edit: this is nearly impossible without special equipment).

As circuits go this cannot be much simpler.


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