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[Crow]

  I am trying to help my aunt with her MF 5000 and am curious what the rheostat beside the Ranco controller does. I looked at the owners manual online as she can't find hers but I didn't see anything about it.

[Scott7m]

It's a high limit switch...  When the boiler over heats it acts as a disconnect til the boiler cools back down to the 130-140 range.. 

[RSI]

It's a high limit switch...  When the boiler over heats it acts as a disconnect til the boiler cools back down to the 130-140 range..

Didn't they put a fan speed controller on them for a while? I think they just used a ceiling fan speed control.

[Scott7m]

It's a high limit switch...  When the boiler over heats it acts as a disconnect til the boiler cools back down to the 130-140 range..

Didn't they put a fan speed controller on them for a while? I think they just used a ceiling fan speed control.

Maybe years ago...   Not sure

[Crow]

Insert Quote
 



Quote from: RSI on Today at 08:05:03 PM
Quote from: Scott7m on Today at 07:25:05 PM
It's a high limit switch...  When the boiler over heats it acts as a disconnect til the boiler cools back down to the 130-140 range..

Didn't they put a fan speed controller on them for a while? I think they just used a ceiling fan speed control.

Maybe years ago...   Not sure

It does look like a ceiling fan control and the furnace is 4 years old (so I'm told)

[yoderheating]

 Yes it was to control fan speed but all it did was burn up fans when it was turned down. Keep that thing on high unless you want to replace a fan soon.

[Crow]

Thanks for the reply's. Yoder - it is on high and she said she has never moved it because she did not know what it's for.

[yoderheating]

 I have to admit every time I see a furnace with one of those on it I steal the knob so its hard to move it from high.