GROUNDING TRAILERS IN MOBILE HOME PARK

[frankfloyd]

IMA INCREASING A 200AMP SERVICE TO 400AMP SINGLE PHASE FOR FIVE MOBILES. THE SUB FEEDERS IS A THREE WIRE SYSTEM, NO GROUND,THE INSPECTOR WANTS ME TO INSTALL A SEPARATE GROUND WIRE TO EACH TRAILER.CAN I DRIVE TWO GROUND RODS for each trailer and connect the #4 the the frame and the sub panel using 250.32 exception #3
FRANK FLOYD #25496

 

[charlie b]

Re: GROUNDING TRAILERS IN MOBILE HOME PARK

Please turn off the ALL CAPS feature a bit earlier in your next post. It makes the post more difficult to read. It is also considered impolite, as though you were SHOUTING at us.

I think you are confusing the concepts of "equipment grounding conductor" and "grounding electrode (rod)." What are you trying to accomplish, and what are you trying to avoid having to do? Also, what version of the NEC are you working under?

 

[hurk27]

Re: GROUNDING TRAILERS IN MOBILE HOME PARK

By Frank: CAN I DRIVE TWO GROUND RODS for each trailer and connect the #4 the the frame and the sub panel using 250.32 exception #3

No, But you can install a disconnect and grounding electrode at each trailer just outside the skirting, use the 3 conductors to that point then run 4 conductors into the panel inside of the trailer. keeping the grounds and neutral separate, This means you have to have the grounds on one buss and the neutrals one an isolated buss. At the disconnect the neutral must be bonded to the grounding conductors and the grounding electrode!
This would be the only code compliant way to fix what you have.
Most trailers come with the neutrals isolated from the trailer grounding and just using ground rods will not provide a low impedance path back to the source. The resistance of Earth is to high to fault a breaker and doing this will cause all that is grounded to the trailer to become hot as in 120 volt to earth, Which could cause someone to be hurt. Then you wind up in court fighting for your freedom.

The NEC or HUD 24 CFR part 3280 does not allow a three wire connection to a trailer because too many have been killed from electric dryers, water heaters or any short to the trailer grounding, Older metal sided one was the worst but a kid grabbing the water faucet or any thing that is bonded to the trailer grounding, can be just as dead!!! and you would be on the hook.
If you think I'm trying to scare you well I am!

 

[allenwayne]

Re: GROUNDING TRAILERS IN MOBILE HOME PARK

Wayne as I have not done much in way of trailer parks or mobile home parks.So what you are saying is that. Regardess if there is a 30 a 3 wire receptacle outlet or a 50 a 4 wire receptacle outlet,the sub panel that feeds each site must have an isolated ungrounded conductor the same as in any sub panel.Correct ?

 

[hurk27]

Re: GROUNDING TRAILERS IN MOBILE HOME PARK

By Allen: the sub panel that feeds each site must have an isolated ungrounded conductor the same as in any sub panel.Correct ?

Were not talking about RV's but manufactured homes.

A 2-pole 3-wire 30 amp receptacle on a 120/240 volt 3-wire service would be a violation if it fed the trailer directly. One the code requires a minimum of 50 amps unless it meets the exception 1 to 550.10(A) which would allow a 40 amp, but in no case is a 3-wire cord or receptacle allowed, even if it is an RV. (unless it is a 120 volt only circuit)

Allen not the feeders to the disconnect(sub panel?) but the feeders from the disconnect (sub panel) to the trailer.
It does not matter if it is cord and plugged connected (Life Line) or permanently connected by feeders in conduit, it has always been required to provide a 4-wire connection to the panel inside of the trailer, and the EGC has to be insulated. The exception to 550.33(A) only allows a 3 wire connection if there is a disconnect between the service equipment and the trailer, this 3-wire connection has to end at the disconnect and then it is required to have 4-wire into the trailer that includes an insulated EGC.

Read 550.33(A)

550.33 Feeder.
(A) Feeder Conductors. Feeder conductors shall consist of either a listed cord, factory installed in accordance with 550.10(B), or a permanently installed feeder consisting of four, insulated, color-coded conductors that shall be identified by the factory or field marking of the conductors in compliance with 310.12. Equipment grounding conductors shall not be identified by stripping the insulation.

Exception: Where a feeder is installed between service equipment and a disconnecting means as covered in 550.32(A), it shall be permitted to omit the equipment grounding conductor where the grounded circuit conductor is grounded at the disconnecting means as required in 250.32(B).

What I was pointing out is the exception would allow him to install a disconnect at the trailer, and keep the 3-wire feed then change over to a 4-wire.
This disconnect has to be service rated, shall be located adjacent to the mobile home and not mounted in or on the mobile home. 550.32(A) be mounted at least 2' above grade, 550.32(F) in sight from and no farther then 30' from the trailer. 550.32(A)