Gas fireplaces/mercury flame sensors

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Old 02-18-19, 07:10 PM
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Gas fireplaces/mercury flame sensors

Do some older gas fireplaces have mercury flame sensors? If so, how do you distinguish between a mercury sensor and a thermocouple or thermopile? (See attached photos) Do the mercury sensors break easily?

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Last edited by PJmax; 02-19-19 at 07:25 PM. Reason: cropped/resized pictures
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Old 02-18-19, 07:24 PM
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If it is a standing pilot light....... not intermittent ignition...... then it will be a thermocouple...... not a mercury flame sensor.

I've never come across a mercury flame sensor in a fireplace. The mercury is contained within a metal tube but I guess that tube could be burned open.
 
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Old 02-19-19, 04:35 AM
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When I got into the residential heat & A/C service 50 years ago (wow ,how time flies) this type of pilot safety control was common. The nice thing about this device was that it would reset itself after the pilot was re-lit without having to push a reset button or switch. They can still be purchased. The ones I used were made by White Rodgers. There is no way that I know of as to know when they will fail. They just quit working. Mercury sensors look like a thermocouple but the end that usually has a thread has a a box that is permanently attached to the thermocouple and the box has terminals for wiring. A thermopile has 2 wires on the end to connect to a device or gas valve. They used to come as 2 types; a fat pencil type or a flat wafer type. I do not think that the wafer type is made any more. hope this helps
 
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Old 02-19-19, 07:28 PM
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When I looked again at your pictures..... what you have appear to be log lighter burners. You light them with a match and then they get the logs started. If those are ceramic logs.... then they are just basic burners you light with a match. I don't see any flame monitoring equipment in use.
 
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