I'm looking for input on whether oil-filled motor start capacitors can
develop a 'cold failure' mode. The situation is as follows:

We started having a consistent problem with our submersible well pump since
the temperatures have started dipping to 0ºF this winter.
The first time it happened was the first week of December, when the
temperature hit zero. The water pressure in the house dropped to a trickle
and the tank pressure gauge was down to 10PSI range but the pump was not
running. After some troubleshooting, I hit the 'overload reset' and the pump
started up and all
was well... until January, when the temperature hit zero again. Then the
same scenario--no water pressure, go down and reset the pump controller and
pump starts up. All is well for the rest of the week. Until the next time
the temp hit zero or below.
There is a clear pattern. The pump overload cutout occurs when the
temperature reaches zero or below.
The pump is submerged some 220' below ground surface. The lines leading from
the well casing is 4' below surface of ground all the way to the house. That
should be below the frost line. And since 1973, we have had much colder
winters and no problems with the pump overloading and shutting down like
this.
Once I reset the controller, the pump kicks on and refills the Extrol
pressure tank at the usual rate of speed and reaches the upper cutoff
pressure and shuts off until needed again. It usually stays working until
the next bought of cold weather.
The controller box is in the cellar, which normally maintains around 66ºF,
but on the very cold nights gets down to 60ºF. I'm wondering if the
capacitors' electrical characteristics can change that much because of
temperature if the cap is marginal and on the verge of failure.
I'm at a loss as to what the cause of this behavior is. I doubt that the
pipes at 4' depth are freezing (and if they were, we would not get water at
all once reset), but the overloads only happen on the coldest nights of the
season, and with predictable consistency.
The last time this happened, I had more difficulty starting the pump. I
pressed the reset, but 5 seconds later, I heard a click and nothing
happened. I could not reset it for another two minutes, but after that time
elapsed, the reset button finally clicked in and I heard water rushing in
though the main pipe.
Does anyone have another idea as to what could be causing the overloads on
cold nights? Is it a failing start capacitor?


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Take care,

Mark & Mary Ann Weiss

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