Alan Roten Posted October 18, 2010 Share Posted October 18, 2010 I had an electrician out today to do some work and after he left and I started looking closer at what he did I am puzzled. I asked him to install 2 outdoor receptacles in a single in use box. Each on a separate 20 amp breaker.After he left I noticed the receptacles were only 15 amp. I have several new 20 amp GFIC receptacles siting on a shelf so I decided it would be easer just to change them myself. Once I started doing this the wiring was not what I expected. Each one is on a separate breaker but it looks like they are sharing the neutral and ground.There is one wire coming in to the box. it is labeled "type NM-B 12-3 with ground" the receptacles are wired as follows. The First one had a black, white and ground.The ground and white wire go to the second receptacle along with the red wire.It is it normal for the same neutral and ground to be used for receptacles on different breakers ?When I asked for each one to be on a separate 20 amp breaker should of I specified that 20 amp GFICs should be used?I often use extension cords with shared neutrals and realize this basically reduces the capacity of the neutral by half. Can a 12ga wire handle 40 amps?Can someone explain to me what was done and is it up to code?Thanks Link to comment Share on other sites More sharing options...
Gary Levelius Posted October 18, 2010 Share Posted October 18, 2010 Alan, the first thing to do would be to see if he used two adjacent breakers in the main panel. The typical house breaker panel has three wires from the pole. Two are the hot phases and the third is neutral. On each vertical set of breakers, they alternate which hot wire they are attached to, therfore, the top breaker in your pair would be on one hot wire and the bottom would be on the other hot wire. Since the two hot wires are 180 degrees out of phase (when one is at the plus peak, the other is at the minus peak), the neutral will never see more than the peak current of either hot wire. Since he used 12 gauge wire (which will handle 20 amps), you should be just fine to put in the 20 amp GFCI outlets in place of the 15 amp ones. If I'm wrong, I'm quite sure one of our resident electricians will chime in shortly -Gary- Link to comment Share on other sites More sharing options...
Victory402 Posted October 18, 2010 Share Posted October 18, 2010 Can a 12ga wire handle 40 amps?No!Sorry, he should have run 2 separate 12/2 (with ground), romex cables, with 20 amp outlets. Link to comment Share on other sites More sharing options...
Alan Roten Posted October 18, 2010 Author Share Posted October 18, 2010 Yes Gary they are on top of each other. Thanks for your response. Link to comment Share on other sites More sharing options...
Gary Levelius Posted October 18, 2010 Share Posted October 18, 2010 Victory402 wrote: Can a 12ga wire handle 40 amps?No!Sorry, he should have run 2 separate 12/2 (with ground), romex cables, with 20 amp outlets.Yes, I agree that would have been the proper way, but as the two breakers are on opposite phases, he should be ok for his light display but would have to be very careful for anything else. Ultimately, he should have the electrician come back and do it properly to be absolutely safe since the way he did it may not be totally to code.-Gary- Link to comment Share on other sites More sharing options...
Victory402 Posted October 18, 2010 Share Posted October 18, 2010 I'll tell ya what you can do, clamp an amprobe around that neutral wire with 20 amps pulling on each outlet and see what you get?What gary says makes sense though to me.http://en.allexperts.com/q/Electrical-Wiring-Home-1734/Shared-Neutrals.htmI think you may be ok with it the way it is. Let's wait for one of our master electricians to chime in. Link to comment Share on other sites More sharing options...
cmoore60 Posted October 18, 2010 Share Posted October 18, 2010 According to code. I believe to use a receptacle in this manner (sharing the neutral)the handles on the breaker need to be coupled so that when one side trips they both trip. Otherwise, if only one trips and you are working on the "dead" side you can still have power available to cause bodily harm.When using a circuit of this nature. If the loads on each hot are exactly the same, you should basically see near zero current on the neutral.Chuck Link to comment Share on other sites More sharing options...
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