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Ok as evident in my PVC conduit thread, I am a newbie when it comes to wiring. I want to learn how to do it so I am doing it myself. anyway my question is how many ciorcuits can i share a common with? i have a book that details how to share the common between multible circuits but it says nothing about how many it is safe to do so with. I am running 10 4 outlet boxes in my shop and 2 outlet boxes will be on a single 20A circuit. anyway should i run a separate common for each circuit or can i run one for multible circuits for this application? thanks
 

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generally we only run two per neutral if you have to. What you have to remember is that the neutral carries the unbalanced load. which with out getting into alot of engineering gobblete **** about sizing neutrals and such. I would unless you have a space problem I would go ahead and run a seperate neutral each circuit
 

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Might want to check local codes as well. There's a lot of thing's you can get away with, but aren't up to your local code. Good luck.

Klaus
 

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The most important part about a shared neutral is that you MUST have the two circuits on seperate phases in the panel. If not, you have a good chance of burning up that neutral. :D
 

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Bronken said:
The most important part about a shared neutral is that you MUST have the two circuits on seperate phases in the panel. If not, you have a good chance of burning up that neutral. :D
Nice catch i forgot to warn about that one :( :( :(
 

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Couple questions about your question, I'm an electrician in Canada so these rules might not apply, but up here we are only a max of 12 rec.'s on one 15 amp circuit. I'm assuming when you say "10 4 outlet boxes" you mean that you have 10 x 2 duplex recepatcle boxes. thats fine. If i was doing the wiring, I'd split the 15 amp circuits on to 2 circuits, 5 rec.s on each (14awg if its not too far from the panel) Sharing one neutral. Like it was said above the neutral will carry the "unbalanced load" of the circuits so if you got 10amps on one circuit, and 5 on the other, the neutral will only have 5 coming back. If you have the fusing or breakers right, the neutral should never see more than 15 amps anyway. I'd run a seperate 12awg neutral (size depending on distance from panel) to the two 20 amp circuits they can share the neutral. They (the 15 and the 20 amp circuits) are on different breakers, so there is a chance that you could have say 12 amps on the "15 amp breaker" and 14 amps on the "20amp breaker" both using the same phase for a total of 26 amps coming back on that neutral, now that wire is starting to get real warm... I'm starting to think there might be a rule about different amperage circuits sharing the neutral, but it might just be a "common practice" kind of rule.. I'll get back to you after I read this when I'm not working midnights, I get real stupid with no sleep..
 

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On second thought, seeing as how tools suck up a lot of power I'd split the 15 amp circuits on to 4 breakers, unless you are going to be the only one working in there 90% of the time. For example, Chop saws usually take about 15 amps alone. If your really concearned about tripping the breaker run 2 circuits to each box, that way you can have your saw going and a fan to cool you off plugged in right beside each other. I could probably make a cheesey drawing in Wpaint, or CAD if you want, a fax would probably be quicker, seeing as how my computer skills are limited to surfing porn.
 

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Run 15A tools on a 15A circuit and you can skip your morning jog :flipoff2:

Put 20A circuits in a shop. ;)

Some breaker panels are more idiot-resistant than others for putting both legs of a 3-wire circuit on the same busbar. Normally you use two slots side-by-side with full size breakers. Its the compact & twin breakers where it gets goofy. FP panels are easy to fawk this up on ;)
 

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I hate FP "Stab-lok" panels. Those with these panels might want to go and reseat their breakers that are slowly working themselves out over time. (just push on the face of the breaker, no need to remove any covers). Some Stab lok's work great and never loosen up over time, All the problems I saw usually happened with used breakers, that had already been in and out a time or two.
 

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tippy99888 said:
I hate FP "Stab-lok" panels. Those with these panels might want to go and reseat their breakers that are slowly working themselves out over time. (just push on the face of the breaker, no need to remove any covers). Some Stab lok's work great and never loosen up over time, All the problems I saw usually happened with used breakers, that had already been in and out a time or two.
We call Federal Pacific panels Fire specific around here. First off if you have to work on the panel the breakers have a tendance to fall out and then as they get older they just quit tripping. One of my inspecters tells the story of wiring one directly to ground turning it on and it never tripped it just smoked. Locally I havn't seen one that is less than 25 years old and when we do see them we recommend that they be replaced.
 

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Here is how it is you should never run any 15 amp circuits for a shop imo. The reason is because you are only supposed to uses 80% of the of the available amps on the circuit. Like a 15 amp circuit should only be loaded to 12 amps and a 20 amp circuit should only be loaded to 16 amps. Thats why imo I would not suggest to run 15 amp recepticle circiut in a garage or shop. As for the sharred neutral circuit ie (eddison circuit) there is nothing wrong with it. As said before you just must be sure that you to hots are on diffrent phases. One easy way to tell if they are or not in put them on a breaker and test voltage between the 2 hots. If you get 220-240 they are on seperate phases. If you only get 110-120 they are on the same phase and will overload the circuit. I agree with everybody else fedral pacific does suck, so does Zensco. If you have a decent amount of room in you panel run a few circuits because it suck to be in the middle of a important cut and somebody turns on something else and the breaker trips. Also just remeber you recepticles must be higher than 18 inches off the ground and must be GFCI protected.
 

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Actually, If you hace both circuits on the same phase (which you do not want) you would NOT measure 110-120 volts. You would read 0 volts when meauring phase to phase, so be sure you read 220-240 phase to phase :flipoff2:
 

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High 5,

If you're still having a difficult time, contact me, I'll go over it all with you. Shoot me an email and I'll give you my tel #. I'm just over in Arlington.

In the interest of not having problems with tripping breakers, go ahead and dedicate neutrals with each circuit.



Tippy - The NEC lets you use an allowance of 180VA for each receptacle. You can put 10 receptacles on a circuit and still be OK. When I lay out a shop, I typically put between 4 and 6 receptacles on a circuit.

When it comes to reliable circuit protection, I prefer to forego the residential load centers and opt up for a commercial grade. Cutler Hammer, Square D and GE all make pretty good commercial single phase load centers.
 

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Discussion Starter #15
thanks gummi bear. i think i have it all lined out now though.....well at least i hope so. i got all of the wiring pulled this weekend. my neighbor who does electrical work came over and ok'd everything.
 

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Gummi Bear said:
In the interest of not having problems with tripping breakers, go ahead and dedicate neutrals with each circuit.

Tippy - The NEC lets you use an allowance of 180VA for each receptacle. You can put 10 receptacles on a circuit and still be OK. When I lay out a shop, I typically put between 4 and 6 receptacles on a circuit.
QUOTE]

Like I said, up here (Canada) there are different rules. We're allowed 12 rec.s on one branch circuit. If it was a comercial shop, I'd run more circuits too, similar to your thought about 4-6, but I have a feeling that this is a personal shop/garage so more often than not there won't be a lot of different tools running at the same time. Money being an issue to most of us, it would be cheaper to run less wire and buy fewer breakers.

Just a thought, it might make it easier to give better info, if we had the size of the shop.. and what you plan on powering..
 

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on the thought of independent neutrals, what about grounds? can you share a ground between multiple circuits? also do ground and nuetral need to be the same gauge as main wiring?
 

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I would size neutrals and grounds to the same size as the hot. Unless you have a space problem I would run a ground per circuit.
 

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Cables usually come with the ground/bare at least one size smaller that the conductors. There's a chart is the Code book for what size is required based on the size of OCP (breaker/fuse) you are using.

You can share the bare wire. It must be sized for the largest circuit in the box though. This pays off with conduit especially.... say you run say 4 circuits, you only need one ground.

You can share neutrals. Its just that so many people mess it up and create hazards. Supposing you run a 3-wire circuit (red, black, white), it is VERY important that the red and black are terminated on breakers that fall on opposite bus bars. Normally panels are laid out so that breakers immediately next to each (from top to bottom) are alternating. However, this will not hold true for half-size and twin breakers.

No harm in asking questions.... there several electricians on this board. :)
 

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I think I'm missing why you would bother going to the trouble of sharing neutrals and grounds. Romex comes two wire and a ground. Easier to pull than individual wires for 12 and 10 gage. I'd never even consider 14 ga. in a house much less a shop. Now if you are talking about 8 ga. or bigger, then I could understand running common neutrals and grounds. Except then you are probably talking 220V and you need two hots so might as well run the separate grounds anyway...
 
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