I need to do a follow up, but wanted it separated from the above. Bob Thompson's answer is just the reason you never want to have a house electricion to do major repairs on your motor home.
In short, in home wiring, at higher "loads", either 120volts (plug-in space heaters, microwaves, curling irons, etc) or 240volts (well pump, cook stove, etc), the higher the load, the LESS current is flowing in your neutral wire! In fact because of this, utility companies often reduce the size of the neutral wire. Electricians are allowed to do this as well. Bob Thompson would confirm that. You have to get into electric theory why, but not here!
In our coaches, when plugged into shore power, the same is true. Since the system is broken into 2 busses, the worst that happens is the neutral carries the same current as the line, till the neutrals combine either at the breaker box or the transfer switch, where it is reduced (subtracted).
The potential for problem occures when you use your generator. There are 2 independent windings in your generator. They are in phase, meaning that there isn't the cancellation that Bob Thompson alluded to. Under these conditions, your neutral will carry the sum of the individual currents where ever the wires are combined in a common run. That can happen at the transfer switch to breaker box under your bed, and it can occure between the generator junction box to the transfer switch. That neutral can see upwards to 100 amps. Don't mean to scare anyone, but a house electrician is liable to wire these segments with undersized neutral wire for these runs because they don't understand.
I realize this is "Blah blah blah" to most of you, but just remember to be careful when you turn your house electrician loose on your motor home wiring.
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