old utica boiler not sensing pilot properly... what to do?

Joseph_4

I have a customer with an old Utica boiler (model M150AGBI or 1)

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that sparks the pilot to light but goes back and forth main flame on and back to pilot. I was told someone tried cleaning the sensor and it doesnt help. still doing same thing. Many people on block with same boiler unscrewed the sensor and stuck a thermocouple in there and changed to standing pilot. ( aside from the obvious that if i do that its my liability etc. ..) any better ideas. they arent ready to replace the boiler . Here are some pics.

Thx

Joe

mattmia2

that is a mercury flame sensor. if it is bad they are obsolete. i think it could be replaced with a thermocouple and the self resetting type of baso switch if the timeout for the pilot is long enough to heat the thermocouple.

mattmia2

Actually it looks like supplyhouse has them. My understanding was that they were obsolete.

Joseph_4

Thank you I found it on supply house as you said!!

mattmia2

Probably finding the instructions for that ivory control and reading them to see what its sequence is supposed to be is the first step. I'm not sure if it isn't proving flame and timing out or if it is proving flame and the next step isn't happening. You can check the flame sensor with an ohmmeter or voltmeter, it is just a switch.

Joseph_4

will do

thx

Joe

EdTheHeaterMan

https://www.supplyhouse.com/White-Rodgers-3098-134-Mercury-Flame-Sensor-48-Element-3-Pin-Plug-Bulb-Style-19

This is the part, and it is not cheap. and I have found that the replacement parts don't last very long, 2 years or so. You may want to look into the standing pilot using a thermocouple, but that would require replacing the gas valve and adding the thermocouple which is a little more work but less total parts cost.

https://www.supplyhouse.com/Resideo-VR8300A3500-Standard-Dual-Standing-Pilot-Gas-Valve-1-2-x-3-4

https://www.supplyhouse.com/White-Rodgers-H06E-24-24-Universal-Replacement-Thermocouple

The pilot burner should hold the thermocouple in the same bracket as the mercury flame sensor bulb fits.

The sparker can be removed or can stay as you wish. It may relight the pilot if it blows out for some reason

I remember one customer, After the second flame sensor quit in as many years, I decided to swap out the valve and install a new valve with a spark to pilot control. Using these parts.

https://www.supplyhouse.com/Resideo-Y8610U4001-Intermittent-Pilot-Control-Conversion-Kit