Voltage on Breaker

[Hfalz1]

Why am i getting 9.0V on a breaker that is off in a 3 phase panel? Single pole 20A. Only 4 receptacles on the circuit. Nothing plugged into them no load.

 

[GoldDigger]

Are you using a high input impedance voltmeter? The 9V could be purely the result of capacitive coupling.
Do the conductors run in a common raceway with other circuits at any point?

 

[Hfalz1]

Only 3 circuits in one conduit. ABC phase with neutrals and one ground.

 

[Dsg319]

As others stated. Most likely “ghost voltage”. If your In the profession of trouble shooting a decent amount get your self a fluke 117 or something with low impedance mode (LowZ).

Got one several years ago and absolutely love it.

 

[ptonsparky]

Adding a load at the test points will drop the voltage. Sometimes just another tester.

We used Fluke T+Pros so we all had the same information when testing. IDR the exact circumstances now but we didn't trust what one tester was showing us. Adding a second, then third dropped the voltage each time.

 

[Jraef]

Wiggy for the win...

 

[MD Automation]

Only 3 circuits in one conduit. ABC phase with neutrals and one ground.

Like others have indicated - likely "ghost" voltage.

You say there are 3 phases in the same conduit. And the breaker you are measuring at is one of these phases? But the other 2 are hot?

If so, then you have 3 wires (2 of them hot) running all alongside each other for however long the conduit run is. This makes a really crummy, but still legit, capacitor - and the dead phase just shows up with a small capacitively coupled voltage because it's in the vicinity of the other 2 hots for a long enough length.

You can only measure this with a high impedance meter - because it introduces no load on that leg to drag it down. That ghost voltage will likely disappear the instant you load the circuit with just about anything (except LEDs ). Try plugging in a small incandescent bulb in see what happens to the 9 volts.

 

[zooby]

As others stated. Most likely “ghost voltage”. If your In the profession of trouble shooting a decent amount get your self a fluke 117 or something with low impedance mode (LowZ).

Got one several years ago and absolutely love it.

Would clamp meters (fluke 374, 375, 376) be high impedance or? Thanks.

 

[Dsg319]

Would clamp meters (fluke 374, 375, 376) be high impedance or? Thanks.

Without looking into them and been a while since I had a 375/376. I would say they are most likely high impedance meters.

 

[ptonsparky]

Without looking into them and been a while since I had a 375/376. I would say they are most likely high impedance meters.

Are they that old?
Mine is a 337 and high impedance.

 

[ptonsparky]

2010?

 

[ron]

As an educational reference, here is a NEMA bulletin

https://www.nema.org/docs/default-source/technical-document-library/phantom-voltages_rev_aug_2020.pdf

 

[LarryFine]

I use a solenoid tester for troubleshooting, and a voltmeter only when I need to know the exact voltage.

 

[zooby]

As an educational reference, here is a NEMA bulletin

https://www.nema.org/docs/default-source/technical-document-library/phantom-voltages_rev_aug_2020.pdf

very cool---well ok helpful---Thanks very much.

 

[ATSman]

I use a solenoid tester for troubleshooting, and a voltmeter only when I need to know the exact voltage.

View attachment 2563842

Yep
that's the one I have
no more Phantom volts

 

[mtnelect]

This is why the electronic breakers trip ... "Phanton." voltage.

See my proposal for update to NEC.