This was put into the Code because one manufacturer on the East coast built a manufactured community. He designed the entire thing, and to reduce cost installed the service equipment on the homes. He knew exactly where the service / utility location was for each lot and set the service accordingly. Everything including the meter socket was built on the home and inspected and shipped that way.
HUD allows the meter socket to be put on in the field, because of different utility companies. HOWEVER, installing the service on a home in the field after it has had the HUD label applied is a field conversion and is NOT covered by the HUD label.
The few homes manufactured to the 3 wire system present a problem in the factory when they are high pot tested, i.e. high voltage applied to detect insulation damage, since the neutral is bonded at the home the entire frame and anything connected is energized. Zap the plumber, and the siding man.
It is important to note that manufactured homes that have a label OTHER THAN HUD may be built to the same building code that governs stick built housing and as a result will have a three wire service on them. These are usually inspected and labeled by the State Building Dept.
THE TYPE OF LABEL IS VERY IMPORTANT. Putting a HUD home on a permanent foundation DOES NOT CHANGE the labeling, or change it from a four wire to a three wire service.
HUD rules are based on an act of Congress NOT the NEC. I think they are currently required to comply with the 1993 Code with exceptions that allow panels in closets.
Locally we have four wide units, and two story units, with attached garage. The garage is a good place to mount the service with a feed through panel because it makes it look like a stick built home.
Alan from Elkhart the MH/RV capitol of the midwest.
As one wag said Mobile homes are like drugs. It's OK to sell them but, don't use them.
[This message has been edited by Alan Nadon (edited 04-05-2005).]