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Rick
Rick, HVAC Supervisor
Category: HVAC
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Experience:  40+ yrs. experience as a licensed oil & gas technician.
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Ive got a Robert Shaw 7000MVRLC-NAT safety valve on a Heatilator

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I've got a Robert Shaw 7000MVRLC-NAT safety valve on a Heatilator GC150 fireplace. I've replaced the thermopile (it generated zero volts) with a new one and the pilot stays lit and the thermopile generates ~.329V w/pilot only. When I turn on the main gas, the voltage drops suddenly to ~.15V and the as the fire burns the voltage slower drops until the safety valve shuts down the gas supply. Is this normal for the voltage to drop when the valve turns on? I wonder if my safety valve is defective.

Rickheatdoc :

Welcome to Just Answer, I will do my best to help you solve your problem

Rickheatdoc :

The voltage generated by the thermopile is not related to the gas valve. Thermopiles generate electricity by maintaining a cold junction. This is the part of the device that should not be touched by a flame

Rickheatdoc :

Only the top ~1/4 of the thermopile should be in the pilot flame

JACUSTOMER-21r5lmgv- :

Yep, it's installed correctly.

Rickheatdoc :

if the thermopile is heated when the main burners come on then the voltage output will drop

JACUSTOMER-21r5lmgv- :

The voltage drops from ~0.3V at the gas valve to ~.15V and then slowly drops to ~0.050V and shuts down. Maybe the thermopile is set too high ?

Rickheatdoc :

if the cold junction (bottom 1/2 to 3/4's of the thermopile) is heated the voltage output will drop

JACUSTOMER-21r5lmgv- :

OK, sounds like I installed the thermopile at the wrong height.

Rickheatdoc :

This is the only likely explanation for the symptoms you describe

JACUSTOMER-21r5lmgv- :

Sounds good, you might have saved me $150!!! Have a happy new year!

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