Generator GFCI breaker tripping when starting the well pump

Luc

Luc

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I am trying to get a 1/2 hp 240V Grundfos well pump working on emergency power. All the other 120V circuits are working on the generator subpanel but the CFCI breaker on the portable generator trips when we start the well pump. Anyone know why this happens with the well pump?
Luc
 
witch said:
Or perhaps the starting current of the pump exceeds the what the breaker can handle, what is the KW rating of the generator.

witch
Click to expand...

Hello witch.
Thanks for answering. The generator rating is 8KW.

I took some reading of the pump circuit and there is a 3.8mA current on the ground when the pump is operating. My guess is that the 3.8mA added to the other leakage of the 120 circuits is tripping the 5mA trip sensitivity GFCI. (The pump circuit is in the generator subpanel with the other 120v circuits.)
 
It is the ground (bare copper wire) not the neutral, since there is a no neutral in 240V circuit.

I went to the pressure switch and plugged my ammeter in series between the incoming ground (bare copper) wire from the breaker and the bare copper wire going to the pumptec.
 
I do have a thread going in the electrical question forum. I started a new thread here because the pump was causing the problem. Removing the ground is not an option because it is to dangerous.

Thanks for all your help. We have a few options to solve the problem. We will see what we will do.
 
Have you checked the motor leads to ground with a ohm meter to see if the wiring insulation is starting to break down and leaking enough voltage that the gfci sees this as a short
 
jnaas2 said:
Have you checked the motor leads to ground with a ohm meter to see if the wiring insulation is starting to break down and leaking enough voltage that the gfci sees this as a short
Click to expand...

jnaas2,
We haven't checked that. What values should we expect for a Grundfos 1/2hp pump?
 
witch,

If we remove the ground wire, what protection will we have if we start the pump at the pressure switch and there is an electrical problem? We would get an electrical shock?
 
According to Franklin Electric:

New motor without cable: 20Megohm or more

A used motor which can be re-installed in the well: 10Megohm or more.

A new motor in the well with cables: 2Megohm or more.

Motor in good condition: 500,000 ~ 2Megohm or more.

Insulation damage, locate and repair: Less than 500,000.

A good 8KW generator should be able to run about 6 1/2hp subs.
 
We did the following measurements on the pump. The pump is 1/2Hp Grundfos. Submersible Motor control SA-SPM4. The cable lenght is about 300'. I don't know the pump model but it is over 10 years old.

Current phase A while running: 6.4-6.5A
Current phase B while running: 6.4-6.5A

Main winding resistance Yellow to black: 6.5 ohm
Start winding resistance yellow to red: 19 ohm

Insulation resistance for drop cable plus motor
1) Yellow to ground: 70 000 ohm
2) Red to ground: 70 000 ohm
3) Black to ground: 100 000 ohm
 
I would say your insulation is about gone. Either in the motor or in the sub cable. Ten years is a good long life for most sub motors.
 
I assume that a pump motor with less insulation means that it consumes more electricity. Any other negative effect other then tripping the GFCI?
 
When you get low ohm values on your meter through a motor, it's because some of that signal is escaping out into the water. That is wasted electricity.
 
A shorted motor that still runs uses a little more juice but, not much. If the amps are too high, then it will trip the overload, and the motor will have to be replaced.
 
I've had the same problem with Grundfos pumps

I've used two Grundfos Redi-flo 2 pumps this past year. One rental and one that we just bought and I have the same problem, the GFCI breaker on the generator keeps tripping. The only way I've been able to get around it is to use a generator without a breaker.

I also tried calling the people at Grundfos and have had no luck.
 
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