Thermal Fuse Blowing Out on Hot Water Baseboard Furnace

Old 11-06-06, 01:31 PM
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Question Thermal Fuse Blowing Out on Hot Water Baseboard Furnace

Hi -
I have a natural gas fired furnace with a multi-zone hot water baseboard heating system (hot water heater is separate). It's a Crown Aruba like this one:

This is installed in a room that about 12x12 in our basement which doubles as a laundry room. The room gets very hot - maybe 80 degrees - and thats with one of the small basement windows in that room open (and it's probably in the 40's at night here now).

I've gone through at least 2 thermal fuses now (looking at the pic there is one in the top third on the right side- you can see the hole for it - the fuse is located in the air plenum behind there.)

It seems to me like it shouldnt be blowing that fuse, and the cause of that is it's heating up too much or not exhausting (I do have a CO detector fairly nearby just in case). The exhaust actuator is opening up the flapper, as I see it side indicator screw open and closed. I also sweeped the chimneys out and checked the duct work for any obstructions, but everything looks clean. I thought it was a problem with the controller, but with the temp getting that high in that room, it seems more like it is really thermally faulting the fuse...

Any ideas???
Old 11-06-06, 06:37 PM
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Thermal Fuse

I suggest you get a boiler tech in there to inspect & clean the boiler. I don't mean the burners like most people when servicing a gas fired boiler will do, I mean the flueways in the boiler. These thermal fuses blowing are an indication of a restriction in the flueways or some place else causing heat to back up & blow the fuse.

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