?

[resistance]

1st Q: What role does the EGC -outside of providing a path for fault current, and prevention of objectionable potential above ground-play when operating a 240v motor load?
2nd Q: If you have 130v between the EGC and L1, And 100v between the same EGC and L2 what does this mean.

 

[charlie b]

1st A: None.
2nd A: An unbalanced load on the panel as a whole, perhaps. I would check the L-N voltages for both phases, at the power panel.

 

[jumper]

Loose noodle?

 

[LarryFine]

2nd Q: If you have 130v between the EGC and L1, And 100v between the same EGC and L2 what does this mean.

Depends; does the same imbalance appear between the lines and the neutral?

If so, bad service neutral; if not, bad EGC.

 

[bphgravity]

The only purpose of an EGC is to provide an effective fault path. It serves no purpose during the normal operation of the premise wiring system. I'm not sure what "prevention of objectionable potential above ground" means.

For question 2, are you refering to the system in general or the same motor circuit identified in question 1. If so, is the voltage reading while the motor is on or off?

 

[resistance]

I checked the main service, and the L-N was good.
@ the load (Motor) there is no N.

For question 2, are you refering to the system in general or the same motor circuit identified in question

I guess I should say it's the cable [feeder] (10-2 with ground) from the main service rated panel to a remote non-service rated panel. That shows the imbalance.

feeder1. If so, is the voltage reading while the motor is on or off?

I'm speaking on the source without the load (motor) attached.
Just curious. Seems the motor has been running for 20 years with no problems, but all of a sudden the motor went down. They have a number of code violations at their house, not to mention they had the Well Pump specialty electrician install a somewhat new well panel (installed with a violations). I believe he also messed with the disconnect--seeing that the line and load wires where reversed.

 

[resistance]

Excuse the drawing--this home computer is extremely old:

 

[480sparky]

Open / loose service neutral. Turn other loads on & off, and see if the voltages change. If they do, that's the problem.

 

[resistance]

Ok, didn't think to do that:roll:!! I will check back tomorrow.

 

[Jim W in Tampa]

My bet is a neutral problem at the panel.Just might been using the motor to help balance and could overheat it. Yes find it and fix. As far as the egc it does nothing untill you have a fault and then your happy its been there.

 

[don_resqcapt19]

My bet is a neutral problem at the panel.Just might been using the motor to help balance and could overheat it. Yes find it and fix. As far as the egc it does nothing untill you have a fault and then your happy its been there.

How would a neutral problem cause an issue for a 240 volt line to line load?

 

[Jim W in Tampa]

How would a neutral problem cause an issue for a 240 volt line to line load?

Ok on paper draw out an unbalanced circuit and cut the neutral. Now take a serious look at how the load tries to balance itself. Cuurent would go thru the motor.
Its not easy to see but depending on its size it just might burn up

 

[Jim W in Tampa]

Is also another problem he might have that explains the 100 volts and that is a line with a very bad connection that in effect is like a resister in series. With a 30 volt drop i would thing you see some arcking or burning and would not last long before it burns open or catches fire.

 

[don_resqcapt19]

Ok on paper draw out an unbalanced circuit and cut the neutral. Now take a serious look at how the load tries to balance itself. Cuurent would go thru the motor.
Its not easy to see but depending on its size it just might burn up

The loss of a neutral will not change the current through a line to line load.

 

[Jim W in Tampa]

First step here is for him to track down the cause of being so far unbalanced. 30 volts is major. Start at main breaker

 

[acrwc10]

When you checked the voltage at the main, did you check at the output of the breaker feeding the motor. Maybe you have a loose connection at the main, I would pull the breaker and check for burning on the bussing and then switch the two phase conductors, then see if you have 100v on the other wire. If so the problem is in the main, if the problem follows the conductor then it is the conductor or a splice in the conductor.

 

[acrwc10]

Start with the obvious.:grin:

 

[resistance]

This is a line to line load (240v). No Neutral needed
In this case, the load should operate as intended.

 

[Jim W in Tampa]

This is a line to line load (240v). No Neutral needed
In this case, the load should operate as intended.

Yes but we must find out the cause of the 100 volt issue. Is it a neutral problem or is one of the legs making a very bad connection or this is a very long run and 1 side is heavily loaded.
As said fix the ovious first

 

[charlie b]

The loss of a neutral will not change the current through a line to line load.

The current through the motor is not the issue. A difference in voltage from each hot leg to ground, as measured at the motor's location, is the issue. A lost neutral at the panel can cause the two voltages at the panel to become different from each other, as measured to the neutral/ground point at the panel. That would in turn cause a difference in voltages throughout the system.