Replies

1. 
   pm22 | Sep 30, 2002 02:51am | #1

   Jim,

   This is one of those cases in which a diagram would help. I drew up my own and think I got what you're saying.

   You mentioned not wanting to overload this thing if all the lights are on and all three garage doors are being opened simultaneously which is why you decided to use two circuits and two breakers. There is another discussion about 2 wire or 3 wire. The shared neutral in your case would then seem to be carrying up to 40 amps which is not good. If the circuits were on different phases, this could work. The idea of pig-tailing is good. Since you are running 2 pieces of 12-2, why not go all the way and wire them as such?

   Since there are two circuits on the same yoke, the breakers must be tied together or - in other words - a double pole breaker.

   The idea of using a shared neutral is actually easy to understand but hard to explain - sort of like religion. Perhaps Dan's Wiring Page may help you. You seem to know just enough to get in trouble. Do you have a permit?

   -Peter

   After you take away what's right, all you've got left is what's left.

1. 
   fireball | Sep 30, 2002 03:26am | #3

   Jim,

   If you have a 220v sub-panel in your garage,then there are two pieces of hot bus , which are opposite sides of the same single phase.The two top breakers(#1 on the left,#2 on the right)are on the same piece of bus.The next two down(#3on the left,#4on the right) are on the opposite bus.It alternates all the way down in a single phase panel.You knew that much,right? So when you ask if it's OK for the two circuits sharing a neutral to be on the same bus (1,2) the answer is no.Peter's right if you had 20 amps on #1 and 20 amps on #2, you'd have 40 amps on the neutral.But if you put the circuits on #1 and #3 circuit breakers (opposite pcs.of bus) the neutral would only carry the imbalance of the current,or 0 amps in our example.K?K.

   Now,is it kosher to have two circuits on the same receptacle?That depends on your local authority having jurisdiction.When I wired apartments in the early 80's my local inspector wanted the two required 20 amp small appliance circuits for the kitchen at each receptacle,just as you've wired yours.His opinion was that people will have the toaster and the coffee pot plugged in next to each other on the counter,so there would be less circuit loading if every receptacle had a black and a red circuit at it.The inspector we have now won't allow that.His theory is that an inexperienced homeowner trying to replace a receptacle is apt to get into trouble with 220v on the device.He wants kitchen receptacles alternated all black,all red.Do you know anyone locally who would know what your inspector requires?

   Barry

1. 
   jhausch | Sep 30, 2002 09:11pm | #5

   Thanks for the reply Barry,

   This is where I am at for now - I put the two conductors to the same breaker.

   One hot runs to one side of the recepts, the other hot runs the switched side.

   I will check the device loads when I get them (door openers and overhead lights) to see if I am running close to the edge.  I am not sure about starting newer flourescents, but I assume that the big current hound on the circuit will be the starting current for the door opener electric motors. 

   If it looks like I am not cutting it close with a 20A circuit I will leave it as is.  If it is too close I will switch to a 2 pole breaker and split the hots. (and put a note in the boxes since the other hot will not be red, but rather a white with black tape)

   I see the guy's point when considering the home owner getting confused with the blk, red, and wh in a regular receptacle.  It would be pretty easy for someone to miss the fact that the little tab was broken off the old recept.

   I attached a very crude dwg.  The reason it is a more literal dwg and not a regular circuit diagram is that I wanted to represent where I wire nutted stuff together and how I ran the two 12/2 cables.  Because of the way I did it, there is a white lead with black tape cut short and wire nutted in the panel that is also not connected in the first gang box.  I would prefer it was not there at all, but I guess this is OK.

   (The diagram is posted on another entry. )

   Steelkilt Lives!

   Edited 9/30/2002 2:44:59 PM ET by Jim

1. 
   BillHartmann | Sep 30, 2002 09:44pm | #6

   A couple of thoughts.

   First I would not have done this in the first place. All you are saving is the cost of a box and recptacle (or 3). I would have just made the lighting onces separate and eliminat any confusion.

   But you are at this point. One thing is that not all breakers allow two wires under the terminal, but SD QO's do for the small sizes.

   And now you have the neutral from the switch tapped up which will be confusing for some one in the future.

   But if I where going to add the 2nd breaker, then I would break the tab on the neutral side of the recptacle and wire that one to the 2nd circuits neutral. Then it is clear that those are two separate circuits.

2. 
   jhausch | Sep 30, 2002 09:53pm | #7

   The breakers are Square D's

   here is the drawing

   Steelkilt Lives!

   Edited 9/30/2002 2:54:56 PM ET by Jim

1. 
   bake | Oct 01, 2002 03:55am | #8

   Does code allow 2 seperate wires to terminate under 1 breaker?

2. 
   Gunner | Sep 30, 2002 03:25am | #2

   Consider a pro. If your putting a twenty amp breaker on 14 gauge wire you have already made a fundemental error. I'm not trying to be mean or start an argument but that is something you should know about before taking on anything.
1. 
   jhausch | Sep 30, 2002 09:02pm | #4

   That was a typo.  You must have caught it before the edit.  the 20A breaker is correct, the wire guage is actually 12, not 14Steelkilt Lives!