Originally Posted by
Van Huskey
Many if not most kitchens today are wired on multi-wire branch circuits due to the 2 circuit requirement (where both circuits are close together) and the need for them to be GFCI protected. You put a GFCI receptacle in the first box for each branch then the rest of them can be protected of the initial GFCI down the line as long as you wire the GFCI in the proper fashion. The whole thing takes wonderful advantage of out of phase hots sharing a common. The one thing you HAVE to do is make sure the two hots are out of phase, the normal and easiest way to make sure this is the case is put both breakers side by side or use a 2 pole breaker which you would do anyway if you want a mixed voltage circuit like Rod is talking about.
I use multi-wire branch circuits to run 120v around the shop. By running 12-3 to around to each double box (not suggesting a home run for each unless you need that sort of capacity) you can wire 2 duplex outlets each with 20 amp capacity but without having to run two 12-3 wires.
You could also put GFCI breakers in as John mentioned which as long as your panel is close would work but it usually costs more than GFCI outlets.
Let me go into more detail and it'll help clarify my question.
First, my understanding of what Rod stated is that he runs a three wire (two hots and a neutral) multidrop circuit. That is, his three wires go to one box, then daisy chains to the next box, etc. At each box, he puts a 230V outlet and a 115V outlet. If this is not true, than my question is moot.
Next, the way a 115V GFCI works is by summing the current between the appropriate hot and the neutral. That is, at any instant, the current into the GFCI is equal to the current out of the GFCI. This means that the current in the hot is exactly equal and in an opposite direction to the current in the neutral. If someone touches the hot, some current flows to ground which means that it does not return through the neutral, and the two currents are not equal and opposite causing the GFCI to trip. So if you put a GFCI on two wires (one hot and the neutral) at one end of a 3 wire circuit and tail off of that, the GFCI won't work because the currents between the hot and the neutral will not be equal and opposite as soon as you use both sides of the circuit.
Given that, I have difficulty seeing how you could GFCI protect Rod's setup, except by putting a GFCI in each box on the 115V circuit.
It would not be possible to put a GFCI in the first box and chain the other outlets off that GFCI. At least, I don't see how it could be done.
Mike
Last edited by Mike Henderson; 02-20-2011 at 12:54 PM.
Go into the world and do well. But more importantly, go into the world and do good.