Help with a safety question

Status
Not open for further replies.
D

dm9289

Industrial Maintenance Electrician
Location
Pennsylvania
Occupation
Industrial process repair/ maintenance Electrician
A multi unit apt
Building feed grounded neutral
After meter 3 wire feeds (no gnd) feeds to apt panel
Apt panel neutral is grounded.


Why is this dangerous?????
Line to line fault breaker trips
Line to neutral breaker trips
Receptacle Outlet box hot falls off hits metal case, gnd on NM cable brings current to panel, from panel neutral completes circuit breaker trips

I am sure I somehow am missing something help please. Yes I work nights lol

Dave
 
dm9289 said:
A multi unit apt
Building feed grounded neutral
After meter 3 wire feeds (no gnd) feeds to apt panel
Apt panel neutral is grounded.
Click to expand...
Assuming that the meters feed the panels which contains the service disconnects there is nothing that is dangerous. That is normally how the service would be wired. There would be no EGC's ahead of the service disconnects.
 
Hopefully the “grounded neutral” meant by a GEC. Also after panel hopefully no 3 wire 120 V loads with a bootleg EGC. As Tom stated also depends on type of raceway.
 
The reasoning behind four wires past the service disconnect is if the neutral became disconnected for some reason, such as a bad connection, everything grounded by it becomes “hot”. It can happen on the utility side too, but the code writers decided for practicality to just start it at the service disconnect. Same as old three wire dryer and range receptacles. Cost of extra wire exempted those for a long time. Sure, the likelihood of the neutral becoming open is low, but that is the reasoning behind it.
 
tom baker said:
Does each apt have a service disconnect, if so where?
What type raceway between meter and apt panel?
Click to expand...
In basement each apt has fused disconnect. No raceway after disconnect 3 wire SE.
 
infinity said:
Assuming that the meters feed the panels which contains the service disconnects there is nothing that is dangerous. That is normally how the service would be wired. There would be no EGC's ahead of the service disconnects.
Click to expand...
After meter fused disconnect 3 wire SE leaves no gnd
 
Greentagger said:
Hopefully the “grounded neutral” meant by a GEC. Also after panel hopefully no 3 wire 120 V loads with a bootleg EGC. As Tom stated also depends on type of raceway.
Click to expand...
Main building feed terminates in a fused disconnect. Neutral is connected to grounding electrode system there.

Several meters are connected together via wire way and rigid till after meter wires connect to fused disconnect in basement 60amp and from there transitions to SE cable no Raceway to a main lug panel
 
hillbilly1 said:
The reasoning behind four wires past the service disconnect is if the neutral became disconnected for some reason, such as a bad connection, everything grounded by it becomes “hot”. It can happen on the utility side too, but the code writers decided for practicality to just start it at the service disconnect. Same as old three wire dryer and range receptacles. Cost of extra wire exempted those for a long time. Sure, the likelihood of the neutral becoming open is low, but that is the reasoning behind it.
Click to expand...
Thank you the problem is an entire apt for elderly is affected I’m trying to find them an out.
I need to get deeper into your reasoning I don’t 100% understand
 
LarryFine said:
The "out" is whether the installation was compliant when installed.
Click to expand...
About 1955 no original diagram.
Building had a fire 12 of 84 units will get complete rewire.
Other units federal pacific boxes they need replaced but can’t pass inspection with 3 wire some of the boxes look like this ugh
 

Attachments

  • IMG_6727.jpeg
    IMG_6727.jpeg
    430.7 KB · Views: 7

Attachments

  • IMG_6891.jpeg
    IMG_6891.jpeg
    65.9 KB · Views: 4
dm9289 said:
Thank you the problem is an entire apt for elderly is affected I’m trying to find them an out.
I need to get deeper into your reasoning I don’t 100% understand
Click to expand...
Think “open neutral”, the loads will try to find an alternate path back to the source. Which can be a person touching something that bonded to the neutral. This only happens if the neutral is compromised. Extreme voltage drop can also cause voltage potential, usually from appliances to metallic water systems that have been bonded at the entrance.
 
tom baker said:
Does each apt have a service disconnect, if so where?
What type raceway between meter and apt panel?
Click to expand...
Tom looks a lot like this but no conduit between disco and panel
letgomywago said:
Might need to insulate the Nuetral on the SE cable. Run this by your AHJ before though.
Click to expand...
the neutral is currently insulated so that’s good. I was currently thinking like you were with the ground but see the pic I think it’s no bueno
 

Attachments

  • IMG_6898.jpeg
    IMG_6898.jpeg
    350.3 KB · Views: 5
  • IMG_6901.jpeg
    IMG_6901.jpeg
    320.7 KB · Views: 5
dm9289 said:
Tom looks a lot like this but no conduit between disco and panel

the neutral is currently insulated so that’s good. I was currently thinking like you were with the ground but see the pic I think it’s no bueno
Click to expand...
That's for new installations. It's still permissible to add a ground after the fact atleast for branch circuits. Look at 250.130
 
Status
Not open for further replies.
Top