Sears 387.9255 Aquastat


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Old 01-06-15, 06:24 AM
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Sears 387.9255 Aquastat

Hello Everybody,

Yesterday one of the tenants called me because the heat is not shutting off. I went there and the temperature was reading 80 degrees and the thermostat was turned off (digital Thermostat). I tried playing with the thermostats and hit the reset button, the circulator stayed on. I pulled the thermostat of the wall to make sure it was not stuck on and the circulator stayed on. It stayed on for a good 10 -15 minuets then it stopped. I lowered the max setting to 140 degrees and checked the wiring and made sure everything was ok. There is a selector switch on the side of the aquastat with two options, one is auto and the other is manual. It is set to auto. There is a note on the cover stating manual for self gen gas valve which I have no clue to what it means. I compared it to the other boiler and it was set to auto too. I don't know how old the boilers, but it must be really old to have a sears aquastat on it. Do I have a bad auqastat.Is there a direct replacement for the Sears 387.9255?

Thank you,
 
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Old 01-06-15, 06:35 AM
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There is a note on the cover stating manual for self gen gas valve which I have no clue to what it means.
Systems which use what is called a 'millivolt' gas valve, can operate without a source of power. Switching to "Manual" will cause the gas valve to open and the burners to fire. This can be used for a minimal source of heat in the event of power failure.

Do I have a bad auqastat.Is there a direct replacement for the Sears 387.9255?
Possibly... maybe even probably...

Can you photo the aquastat? Sears most often used 'branded' controls from other manufacturers.
 
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Old 01-06-15, 06:57 AM
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Hi Trooper,
Thank you for explaining the self gen piece. I can't take a picture now, I'll try to do it after work.
 
 

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