Electrical Feed question

[buddy]

Hi, Why do mobile homes require a 4-wire feed (from the disconnect box on the pole and into the home's main breaker box) instead of a 3-wire? Could a 3-wire feed be connected and still have a safe hookup?
Thanks.

[Eugene]

It is a code requirement. All MH require a four wire. The ground and neutral are isolated for an extra safety measure.

[Kevin]

The reason for the 4th wire. the first 2 wires are the "hot"current carrying conductors. the third wire is a neutral. which is also a current carrying conductor. it carries the unbalanced load between the two hots. it is not a ground. the forth wire is the ground. it is not a current carrying conductor. The NEC says that if your home panel is more than a stud space away from your meter then you have to treat the panel as a sub panel which means the grounds and neutrals are seperated. if your panel in your home was a stud bay away from the meter then you could treat your panel as a main service and the ground and neutral would be connected. but thats only allowed at the meter, and i have yet to see a MH where the panel was only a stud bay away from the meter. they are usually 10 feet or more away. if you look in the electrical panel of any MH you will see that they come from the factory where all the neutrals land on one (the Neutral) bar and the grounds all land on another (the ground) bar.

[buddy]

Thanks Kevin and Eugene. I looked at the neutral conductor and grounding bars in the 200 amp MH panel and they're separate and not bonded as you pointed out. Today I got some good advice from an electrician and learned how to do it properly. He said the neutral and grounds are bonded at the service disconnect box on the pole. There will be a 4-4-4 gauge 3-wire aluminum cable from the disconnect to the MH panel, and the solid ground wire from the MH ground buss connects to the frame and to a ground rod at the MH. He said the newer MH's use the four-conductor service cable, but mine is a 1985 model and the panel is not made to accept the 4th large-gauge ground wire of a 4-wire hookup.

[Kevin]

I think i understand what youre doing. it sounds like a hokie thing. your home requires 4 wires as you verified by opening the homes electrical panel. your electrician is right the ground and neut are bonded at the service(meter). if you run only 3 wires then drive ground rods then 1. you are relying on the conductivity of the earth (Dirt)only as a path for fault currents. which doesnt meet NEC code requirements. so your panel will need to be modified so that the grounds and neuts will be bonded in the panel. I regularly hook up on average 3 Manuf. homes a week. I buy my wire from Home depot. i get whats called URD or Sweetbriar. it has 2 aluminum conductors that are 4/0 in size and one alum conductor that is 2/0 in size. to get the 4th wire i also get a cut of #4 alum. i then install them in conduit from the meter to the home. no ground rods needed. no jury rigging of the homes electrical panel. rarely but sometimes. if there are 4 wires stubbed up under the house we will run a wire commonly called SER (4 conductor)it is a romex type product with all 4 of the wires wrapped together in a single sheath. it sounds to me like the wire youre talking about. accept it is what we call SEU (3 conductor) and it is the wrong product.

[melynn]

I Just purchased a mobile home form person. When the movers got ready to move the single wide, they cut the electrical wire (four wires). Couldn't they have just unplugged it? Where can I find a step by step guide to rewire the cords, and plug it in to the outlet? I am in Delaware.

[rmurray]

Boy you bought an old home....pig tail plugs are a flash of the old days...There have not been plugs on manufacture/mobile homes since 1976....Some crews cut the wire because some customers try to use it..but almost always it would not exactly fit again..Cutting it keeps you from trying to splice a piece in to make it fit..Which cannot be safely done.....Since you do not know exactly how to do this invest in a local electrician to do this wok...There should be lots more outside than a female plug..there should be a box with breakers and meter base...Find a skilled electrician by calling a local dealer and ask for a referral...Most local governments require an electrical permit in addition to a building permit..this is usually gotten by the electrician....Local rules vary a lot..get proper info from your building department....