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Spill Switch getting stuck on Weil-McLain EG-45 Gas Boiler

6 years ago

I have a Weil-McLain EG-45 SPDN Gas Pilot boiler for my house. I started to
have problems about a year ago where the spill-switch would get stuck, causing
the Vent Damper to stop working, therefore no heating until I would have to
manually press the little button on the spill-switch to re-start it. Then
everything would work great for a while (up to 3-4 months).

Unfortunately this started to happen more and more often (from once in 4
months, to once in 3 two months and so on).

I then decided to change my Spill Switch (twice), using an original Weil
McLain replacement part # 510-300-013, and now just recently, I installed a new
Vent Damper (made by Field Controls). Again, everything worked for about 2
weeks and then the same situation reappeared.

I have also exchanged the Thermostat (Honeywell RTH7600D) about 4 months

The interesting thing: This "stuck" problem usually happens when the Gas
Boiler unit is NOT needed to work for longer periods (meaning its warm enough in
the house for a half of day or even a couple of days, and it does not have to
keep working consistently, as it does in the middle of winter). So the argument
that the Spill Switch is "overheating" and fails to re-start is not applicable
here. I have also checked the two wires that go into it for corrosion, but
they seem just fine.

I am also pretty sure that the chimney is clean. We have a protective cap on
top of it for the last 3 years, and I think if it was clogged, the damper vent
would stop working within hours.

Can anyone please tell me what else can I try replacing or what can I do?
The gas flow is normal, the thermocoupler was just replaced and works just
fine. Winter is pretty much over for this year, but I am always thinking

All suggestions are appreciated!

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