First time experience after 29 years. Would appreciate some feedback.

[jango]

Hi all,

Today I eliminated power to an original sub panel in a garage to relocate it and I pulled out the sub feed conductors that were feeding it from the meter/main/load center service panel. The main service panel also feeds other loads including another small sub panel upstairs that was added during a previous remodel that was before my time out there and is completely separately fed from the original sub panel that I was dealing with in the garage.

After taking out the branch circuit breakers and disconnecting the branch circuit neutrals from the garage sub panel, I got shocked (and was very shocked to actually receive a shock!). After some preliminary investigation, I discovered that when turning on ONE single pole circuit breaker in the upstairs sub panel, that in turn 120V energizes four different individual branch circuit conductors in the garage sub panel. One conductor that becomes energized is a white conductor which was originally landed on the neutral bus and has two associated hots (black and red) going out in the same conduit. There is also another conduit with a black, red, white, and all three of these conductors are energized at 120V individually to ground when the same circuit breaker is turned on in the upstairs sub panel.

Now I know that I'm looking for a connection or connections that are not suppose to have been connected, but any feedback or previous experience on such a situation would be very much appreciated.

 

[GoldDigger]

There is a possibility that there is a Carter/California/whatever three way circuit with the two hots being fed from different panels (but same phase.)
One switch position (nominal with the light off) will lead to the two hots being connected together through the bulb(s).

Look at a schematic for that circuit and notice that configuration. The other OFF combination ties the two neutrals together instead, with associated shock and GFCI trip problems.

Sent from my XT1585 using Tapatalk

 

[junkhound]

Does not sound like your situation, but was replacing some K&T 50 years ago in an attic with the meter pulled.
Received a good shock cutting out some wires and the wires had a good spark also.

Turned out 6 different houses (all built circa 1943 for housing for a defense plant) fed from same distribution transformer, house I was working on had the only functional ground of the 6. Just ground circuit potential was cause of the shock and arcing.

 

[GoldDigger]

Does not sound like your situation, but was replacing some K&T 50 years ago in an attic with the meter pulled.
Received a good shock cutting out some wires and the wires had a good spark also.

Turned out 6 different houses (all built circa 1943 for housing for a defense plant) fed from same distribution transformer, house I was working on had the only functional ground of the 6. Just ground circuit potential was cause of the shock and arcing.

Sounds more like your site had the only functional neutral to POCO. That would put all of the return current for the other 5 going through your ground (shared water pipe/main) to your neutral. You could get the full 120V that way if you cut the neutral.

 

[junkhound]

get the full 120V that way if you cut the neutral.

Yep, that is what I meant, you phrased the situation for better understanding.

 

[Sahib]

The lesson is the main disconnect should be switched off; switching off subpanels to work on them is not enough.