zinsco sub panels

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velbek

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Electrician
Hi,
I'm replacing Zinsco sub panels in a 6 unit apartment building. Each panel is 3 wire (2 hots, neutral) and uses the Flex conduit for ground.

My question is if I have continuity between the neutral and panel shell then that means the ground and neutral are bonded near the main disconnect and I should not bond the neutral bus to the shell at the sub panel, right?

Thanks
 
In a feeder panel the neutral is never connected to rhe egc. The sbj is at the service. Flexible metallic conduit is limited to 6 ft as an egc, and the ampacity is limited depending on the size. What is the feeder ampacity and is it flexible metallic conduit or ac?
 
Most of these panels have a 2pole 50 or 70amp breaker fee

I have seen some of these panels with the neutral bar to ground connection and some without (different buildings) obviously these are 40-60 year old buildings. Feeder conduit is flexible metallic conduit.

I could take apart the main switchgear and check for bonding there but I figured if I just check for continuity at the feeder panel I could bypass that?
 
Yes it would, but why would a neutral and ground be connected anywhere else let alone a receptacle... Also, there are no ground wires so the yoke in the only thing grounding outlets.
 
velbek said:
Yes it would, but why would a neutral and ground be connected anywhere else let alone a receptacle... Also, there are no ground wires so the yoke in the only thing grounding outlets.
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Any connection whether intentional or not introduces parallel current paths for neutral current, and some of it over what is supposed to be normally non current carrying components.

When it comes to intermixing neutral/ground and people that don't know any better having done work on it in the past- expect anything is possible.

I have seen many cases where an EGC was "bootlegged" from a neutral conductor or a neutral was needed but not available and EGC was utilized for the purpose. It "worked" so must be OK.
 
velbek said:
Yes it would, but why would a neutral and ground be connected anywhere else let alone a receptacle...
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If the electric ranges have 4 wire cords and the installer of a new range didn't take off the ground/neutral strap in any of the units, then that will connect the ground/neutral in all the units.

I have a 4 plex w/ zinsco subpanels, 60 amp feed, and electric ranges, so I know that can happen. Most of the subpanels have since been replaced.
 
Barbqranch said:
If the electric ranges have 4 wire cords and the installer of a new range didn't take off the ground/neutral strap in any of the units, then that will connect the ground/neutral in all the units.

I have a 4 plex w/ zinsco subpanels, 60 amp feed, and electric ranges, so I know that can happen. Most of the subpanels have since been replaced.
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That seems to happen a lot - range dryer with 4 wire cord and installer doesn't remove bonding jumper.
 
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