Why is my sub panel still live?

[cdnc]

I have two 200 amp services. One serves the house and the second a garage, pump house and a greenhouse. The main panelis in the garage and feeds two sub panels one in the pump house and one in the greenhouse.

We are replacing the greenhouse with a new building. I'm trying to shut the power off to the sub panel so I can remove the lights and plugs. When I shut the main breaker off in the sub panel, the wiring still seems live when I test it with my tester. When I turn off the circuit in the garage to the sub panel, I still seem to have live wires.

What's going on?

 

[zmaxmotorsports]

What are you checking voltage with?

 

[pattenp]

If you are using a digital volt meter and getting low volt readings such as less than 50V those are ghost readings. Do you have a non contact tester that lights up and beeps when power is present?

 

[cdnc]

It is a contactless tester that beeps. When everything is supposed to be shut off I'm still getting beeps on the panel and in the wiring to the circuits.

 

[ishiboo]

It is a contactless tester that beeps. When everything is supposed to be shut off I'm still getting beeps on the panel and in the wiring to the circuits.

The contactless tester works by "hearing" the AC waveform, it can pick this up hopping from wire to wire.

Use a DMM and measure everything correctly to verify what is actually going on.

 

[wyliesdiesels]

That is typical behaviour with non comtact tester... Check the voltahe with a DMM when in doubt

 

[theoldwizard1]

That is typical behaviour with non comtact tester... Check the voltahe with a DMM when in doubt

Re-read what pattenp wrote. The only way around ghost voltage readings is measure the voltage at a load that you know is on (light bulb) or wire a 25 watt 1000 ohm resistor across the probes of your meter.

It will get HOT very quickly if there is power in the line.

 

[awdblazer]

where are you checking for voltage? sub panel? main panel?
which breaker did you shut off? breaker in main panel or sub panel? cause if you just opened the breaker in the sub panel its still going to be hot to the one side of the breaker

 

[wyliesdiesels]

Re-read what pattenp wrote. The only way around ghost voltage readings is measure the voltage at a load that you know is on (light bulb) or wire a 25 watt 1000 ohm resistor across the probes of your meter.

It will get HOT very quickly if there is power in the line.

No i dont need to reread what he wrote.

When my tester gives me a live reading even though the breaker for the circuit is off, i will get my DMM out and check the voltage. Usually it will give me 30-60v, which is ghost voltage, and my meter has a live icon, which doesnt turn on with ghost voltage.

 

[sberry]

Turn the lights on, switch breaker off, do they go out?

 

[Hornman]

Even if it is ghost voltage you need to determine where it is coming from. Does the power to the main and the line to the sub run in the same conduit?

 

[cdnc]

Ok I made sure all the breakers were off - to the load, the main breaker on the sub panel and the feed breaker from the main panel. As suggested, used my DMM and was only picking up about 0.4V so I was able to disconnect everything. I suspect there a bit of stray voltage as part of the trench may have the main it it, and it may share a trench with a run to the other sub panel and some solar panels.

Thanks all for the help! ��

 

[sands35]

0.4 V is probably a ground loop. Same thing as with those potato powered clocks.