Quick question here guys. In a mobile home with a four wire feed from the pedestal, with the ground and neutral bonded at the pedestal, should the two be bonded in the service panel? I'm asking for my dad who can't use a 'puter.He asked an "electrician" (note the quotation marks), and he said that it's there in normal homes, and it should be in this house. This ain't a normal house. Thank you, Ian A.
Is there anyone on board who knows how to fly a plane?
The "danger" in having the neutral and the ground connected to each other in more than one place is in that this set up a "parallel path." That is, part of the ground wire will always be carrying current- which it is not intended to do. In a mobile home, connected by a cable, the risk is a lot less than, say, in a situation where a section of conduit becomes a "neutral;" but it is still aviolation.
Connect ("bond") the two once- preferably at the point where the utility neutral goes one way, and the wire to the ground rod goes the other.
As to things "always being done...." well, trailer/RV parks are famous for incorrect wiring methods.
If the neutral is bonded at a second location away from where the grounding electrode conductor and the main bonding jumper connect, then there needs to be another ground rod driven and another equipment grounding conductor applied to the bonding jumper at the second location, just as if you were feeding a sub panel with the grounded conductor and the grounding conductor are run with the feeder. In the 2002 code book look at 250.32 for clarification. Although the pedestal does not constitute a separate building the intent is that for each point where the grounded conductor and the grounding conductor are bonded there is a separate connection to earth. What might be acceptable is to connect a separate grounding electrode conductor from the panel in mobile to the existing ground rod.
Look at the outside of the home where the electrical connection goes under the home. Look for the sticker that may still be there. It will read something like 120 / 240 volt FOUR wire. Follow the instructions. If they were meant to be reconnected at the home it would only need three wires. One "danger" of reconnecting is that the frame of the home is bonded to the grounding conductor. Connecting the green to the white wire in the home means you could energize the frame of the home. Alan --