Hot Motor….

[Seven-Delta-FortyOne]

Commercial facility (restaurant) has a 20A 2P feeding a sub panel in the wellhouse

It was tripping repeatedly, I guess when the pressure pump would come on. They told me the breaker felt funny. I said it’s rarely a faulty breaker.

Checked it out today. Breaker feels and functions normally.

Voltage is 244 at the main panel, 239 at the pressure pump motor while the motor is running.

Amp draw is a little high at between 8.2 and 8.7. Nameplate FLA is 8.1

I am unable to replicate the issue, and it apparently hasn’t tripped for the last several days.

The thing that I noticed is that the case of the pump motor, (not the impeller housing) is hot, like too hot to touch.

Ventilation is good, it’s an open shed.

Anyone have an idea what might cause it to overheat like that? And could it be something that could cause an intermittent over-current situation?

Theal overload on the motor has not tripped either, that I’m aware of.

 

[ptonsparky]

It should be danged uncomfortable to hold your hand on a fully loaded motor.

Amp clamp both conductors at the same time. They should net zero. If the .5 amps (8.7 - 8.2) is still there, you have a motor failing.

 

[ptonsparky]

Guessing those readings were of each hot.

 

[Seven-Delta-FortyOne]

I checked them several times as the motor would cycle off and on. It would vary between 8.2 and 8.7.

I know the motors get warm, and I’ve felt a few pressure pumps, but this one seemed unusually warm to me. Could be way off base on that though.

 

[ptonsparky]

If you can, close a valve a bit to reduce the flow. Amps should go down.

 

[Jraef]

Touch is not a good measurement of motor health. That motor has Class B insulation, which means it can withstand 80C over an ambient of 40C plus a 10C hot spot, so 130C max, which is 266 deg F. Humans perceive heat as being too painful at 140F (45C) for 5 seconds. So our threshold is WAY lower than what a motor can safely tolerate.

This motor is also rated for a 1.4 Service Factor, so the amps can be 140% of the rated FLA, although not forever. But a well pump motor should never run forever.

What might make a difference however is “short cycling”, meaning it comes on and off in too short of time periods. You may want to take a look at the pressure switch functionality and settings, such as the hysteresis (cut-in/cut-out settings). Someone may have tweaked it without understanding the consequences.

It’s also possible, as ptonsparky said, that someone opened a valve too much and the added flow is overloading the motor. But as I said, this motor has a 1.4 SF, so that would have had to be a big change in flow. Still worth checking though, for example did they add something to this water system and was it demanding water when you were there to check it?

 

[ptonsparky]

Any way you look at it that pump motor should not be causing a 20 amp breaker to trip. It would need to to go locked rotor or very rapid attempts to start. Maybe an intermittent connection somewhere.

 

[MiElectrician]

It should be danged uncomfortable to hold your hand on a fully loaded motor.

Amp clamp both conductors at the same time. They should net zero. If the .5 amps (8.7 - 8.2) is still there, you have a motor failing.

I've heard of this to check extension cords, never considered it for a motor

 

[Eddie702]

Anything that would cause the motor to short cycle....on-off on-off ....pressure switch.......bladder tank could cause tripping

 

[PaulMmn]

How's the water supply? Not running low on water, is it? Would result in pump sucking air trying to shlurp up the last bit of water. Excessive running resulting in a hot motor.
Does the pipe in the well have a foot valve? A broken foot valve would result in the pump running an awful lot, perhaps overheating the motor and tripping the breaker. You said the overload at the motor hasn't tripped. Does the SquareD box have a reset button??