new panel / old wiring

[Oak]

I'm changing a outside 3 wire/200 amp main disconnect (1986 mobile home-private lot) because I lost half of the breaker due to corrosion. Right now grounding to the panel goes to 2 ground rods 6 feet apart connected to the nuetral bar. 3 wires (2 hot and nuetral) travel underground (conduit from disconnect is only buried 18 inches into the ground) to 200 amp panel in home. My question is do I have to dig down to bring another ground (green) from the outside panel to the inside panel as called for by NEC rules today.

 

[ronaldrc]

Yes you should not just because it is a NEC requirement but it could cause a fatal shock
if you loose your neutral connection. If you lose your neutral between your mobile home
and your outside disc. or panel it would hot your whole trailer body to 120 volts which
would more and likely cause a fatal shock to anyone touching the trailer from the outside
especially in wet weather.

And you need to separate your neutrals and grounds in your mobile home panel and insulate
your neutral bar from the metal panel enclosure inside your mobile home.

Your neutrals and grounding bar will be bonded together in your main disc. or panel outside.

http://home.comcast.net/~ronaldrc/wsb/grd.htm

 

[Oak]

Thanks for the info. It makes sense

 

[readydave8]

I beleive the mobile home was wired incorrectly originally, the ones I hooked up in '86 and earlier needed 4 conductors from pole, neutrals and grounds were separate bars in panel. So no grandfathering would apply, it was done wrong to start with.

 

[Oak]

I don't know if it made a difference at the time, but this is a stick built mobile home (no metal at all except for the 2 main frame rails). I also found while digging today (to add ground) that the conduit (2in) from the main disconnect does come under the trailer about 5ft (18in down) and stops and the wire (Aluminum 4-4-2 ) comes out of the dirt from there and lies on top of the dirt for about 15ft across the undrneath to where it goes into a 2in conduit about 3ft off the ground and into the bottom of the sub panel. There is a small ground (bare copper) from the sub panel to the frame rail.

 

[billdozier]

To me why dig a new ditch? Pull the grounding conductor in the existing conduit,should have room with 2 inch conduit. The pipe needs to have fa connectors transition to carflex up to the down pipe. The small ground is to bond your trailer frame to ground

 

[Oak]

Thought the pipe ended 18in below ground level under the main disconnect and wire was buried from there. Nice to find the pipe under the trailer (clay and rock)

 

[kwired]

I don't know if it made a difference at the time, but this is a stick built mobile home (no metal at all except for the 2 main frame rails). I also found while digging today (to add ground) that the conduit (2in) from the main disconnect does come under the trailer about 5ft (18in down) and stops and the wire (Aluminum 4-4-2 ) comes out of the dirt from there and lies on top of the dirt for about 15ft across the undrneath to where it goes into a 2in conduit about 3ft off the ground and into the bottom of the sub panel. There is a small ground (bare copper) from the sub panel to the frame rail.

Those metal frame rails are the biggest reason to not bond at the trailer panel. If there is a lost neutral they become line voltage or very near line voltage and somebody crawling under the trailer to do any work of any kind ends up dead when they contact one of them while laying in moist dirt. Doesn't matter when it was built, AFIK you were always required to supply a mobile home with separate grounded and equipment ground conductors. I know of a few electrocutions that happened under mobile homes and this is usually why. I don't even care to crawl under one while it has its feeder energized for this reason unless I know more about the conditions - like maybe I am the one that hooked it up.

 

[Oak]

Thanks for the responses, great site and great info.