wiring, best practices...

[the dude]

We finally got our electrical permit approved and I was wondering if there is a best practice guide to wiring. Not the rules and regs, I am current on all of those.

It is "common sense" things that I am unclear on. For an example, is it better to run power to the fixture first or to the switch first. How orderly do my wires in my ceiling need to be? Do you want them straight and together, using more wire, or ran in the shortest run possible from point A to point B.

What would be the best "way" to run this on one circuit. I want the plugs always on and the lights switched at the door. Code stated the wires can be ran on top of the truss if it is under 1m to the roof and you can not drill the trusses:

 

[rotus7]

I'm no electrician, but I have had an electrical class in the construction management program I'm currently in and I learned enough to do some wiring with a little brush up. I don't have a book to suggest but I know there are several on the market that give you a good hands on guide and most likely "best practice" for wiring.

It would be my suggestion to lay your wiring out in an orderly fashion in your ceiling for a couple reasons. First, if there's a problem in the wiring, you can more easily identify the location of the problem. Second, if it's run shortest distance, it cuts down on usable space in the attic. The crook...I mean contractor who built my house had the electrician run shortest distance, and 90% of my attic space is unusable because electrical, cable and phone lines are strung out all over the place, some so tight you can strum a cord.

 

[Piper]

HI Brad

I'd take power from your panel to light switch (over the door) up to the closest fixture (by the diagram the "top left") and then daisy chain one to the next, forming a circle ending bottom left. For your ceiling receptacles, run the wire along the joist and jump off along the closest joist o the box. The receptacles have 2 sets of screws for hot and neutral which you can use to extend the circuit to the 2nd receptacle. I personally like to run along or perpendicular to joists so that it looks nice rather than diagonal as you referred to as done by an electrician.

Hope this help!

Piper

 

[rodnok1]

I agree with Piper on running to switch first, then to ceiling outlets. I would also break your lights up into groups, for the cost of wire and an extra switch or two you can have more control over lighting. As for running all off one circuit, you could put a junction box in the ceiling that would feed down to switches and across to openers.

 

[the dude]

This is the wiring for cheapo lights that you want to turn on for a quick in and out. I have 16 8" T8s to install that will be switched in three segments. Side/side/front

I also have 6 other plugs going into the roof.

As for running to the switch first, any reason for this?? The problem being I was planning to have main/side/side/front/outside for a total of five switches at the door. Running my supply line to the switch means I will have 10 wires coming to the box instead of 5.

Does it matter?

 

[the dude]

I was thinking this, but would like input if I can do it better.

 

[rodnok1]

That would depend on how many circuits are feeding those lights. Meaning you only need one feed wire for each circuit coming into the switch box. You mentioned only using one circuit.. It is very common to have main power to light box first, then use romex down to switch. It gets a little harder to keep tract of hot/nuetral wires, just have to mark them.

 

[the dude]

Only one circuit powering those 10 outlets. We are allowed 12. I figured for low wattage lighting this would be safe. The rest of the garage will average about 6 outlets per circuit on the 110V lines.

 

[Charles (in GA)]

This is the wiring for cheapo lights that you want to turn on for a quick in and out. I have 16 8" T8s to install that will be switched in three segments. Side/side/front

I also have 6 other plugs going into the roof.

As for running to the switch first, any reason for this?? The problem being I was planning to have main/side/side/front/outside for a total of five switches at the door. Running my supply line to the switch means I will have 10 wires coming to the box instead of 5.

Does it matter?

You will need to sit down and figure your box fill and make sure you do not run too many wires in the box.

There is a spiral bound flip book that is on the book racks at Home Depot, Lowes, Menards, not sure what you might find in Canada, as the codes may or may not be different, but this flip book, called CODE CHECK- ELECTRICAL is very handy, and will answer most of your questions. It will show you how to calculate box fill and will answer some of your other questions.

There is not set requirement to run wire to the switch first or to the fixture first, but there are a few restrictions on wire colors. If you go to the fixture first, the wire to the swtich must have the white wire remarked to show it is a hot wire (black in a 120V circuit) and you may not use the remarked, formerly white wire, as the return to the fixture from the switch, that wire MUST be an all black, wire. You may use the remarked wire to carry the power from the fixture down to the switch.

Your wiring will probably be less complicated if you run the power to the fixture first.

If you run the wires in groups along the ceiling joists, do not tightly bundle them, the code addresses derating wire if over a certain number of conductors are in a bundle more than 24 inches long, and even an open bundle is affected. You can run the wires side by side or in the same area, but do not tightly bundle them, such as with tiewraps.

Charles

 

[the dude]

Thanks Charles, I will check at my local Home Depot. I have our local "electrical code simplified" book and have been drawing out routes all day and figuring box fills and the such. I am using the deepest boxes available just incase I run into situation where I need the room. It shouldn't be a problem as far as I can tell.

I am trying to avoid the inspector going "Hey you *******, that will work, but why didn't you do it this way???"

Thanks for everyones responses.

 

[Charles (in GA)]

Let me add, you will be much better off running a completely separate circuit for the two receptacles that will power the door openers. You will ocassionally have reason to disable the openers, by tripping the breakers, but will still want the lighting to operate.

Not sure of the total wattage of your lighting but make sure the amperage of the circuit, since it will be largely or completely lighting, cannot exceed 80% of the circuit capacity (ie. no more than 16 amps total on a 20 amp breaker) since this is a continous load. Code defines a continous load as that which will draw power for more than three hours, and lighting generally falls into this category. This is always a good rule to apply to any circuit to stay on the safe side of things.

As far as maximum number of receptacles on a circuit, NEC 220.14(l) sets a requirement that you calculate loads on general use receptacle circuits at 180 volt-amps per strap (receptacle). Thus on a 120v circuit, with a 15 amp breaker, you are limited to ten receptacles, and on a 20 amp circuit, you are limited to 13 receptacles.

Charles

 

[mulepackin]

Another good book is "Wiring Simplified" by Richter and Swan. It covers alot of what you are asking, and does so in reference to the NEC. They also put out a much larger book called "Practical Electrical Wiring". I rewired my house after an addition, and did everything from the meter base on. I spoke to my inspector in advance about my plans. He drew some schematics out for me about how things should be done, then said "Nothing I've drawn can leave my office", I then said, "I'll bet anything I draw can leave it", I copied all of his stuff and he just grinned. Everything passed on my first go round. Just don't give em the impression you are trying to pull anything over on them.

 

[SteveU]

Another good idea is to use armored cable anywhere that 'critters' can get to it. Few years ago my father-in law's house was 90* F in the winter & the furnace wouldn't shut off so we had to kill power to it. Ran a new thermostat wire & found where the mice had chewed the insulation off & the wires were shorting out on each other. I ran romex from the breaker box to the switch & then up to ceiling level where I switched over to armored cable that they can't chew thru. Costs more but gives peace of mind knowing that it won't cause a fire someday.

 

[fefarms]

A couple rules I try to follow for my own projects.

1) I always run power to the switch first. That way I have a neutral available at the switch if I ever want to run a timer, dimmer, or occupancy center. Also, if the switch is off, I know there is no power to the fixtures, or any boxes holding the fixtures.

2) Don't mix receptacles and lights on the same circuit. It's really annoying to pop the breaker with your table saw, and have the lights go out, while you are inches away from a spinning metal blade.

3) Use 14 AWG wire for the lights, use 15 amp breakers, and limit the load per circuit to 12 amps. The box fill restrictions for 14 AWG are easier to meet, and the thinner wire is more pleasant to work with. There's no reason to "overkill" lighting circuits when you know the load that is going to be on them.

4) Use 12 AWG wire and 20 amp breakers for all the receptacles, especially in a garage or shop where high load tools are likely to be use.

 

[KGorney]

It's also a good idea to "leapfrog" receptacle wiring. Instead of wiring all the receptacles in order, wire every other on a different circuit. It uses more cable, but this way, if you ever have an issue with that circuit, you won't have one whole side of your garage that doesn't have power.
Another reason to keep lights on their own circuit is so your lights don't dim when you run something else on the circuit.
Don't forget to run your garage door opener safety sensor wires now. Running the wires in the walls looks much better than stapled to the sheetrock.

 

[cc_rider]

KGorney's idea of leapfrogging is a good one, and I've heard another way to accomplish it: use 12-3 instead of 12-2, and alternate between the black (hot) and red (hot) at each box. The neutral is common of course, and the red and black are connected to the separate legs in the breaker box. Another bonus of this method is you can pull 220V anywhere you need to; both hot legs are in every box.

Not to rain on fefarms advice, but I never use 14 gage at all. If you're doing it yourself the cost increment is negligible. Plus if you ever decide to add an outlet or whatever, you won't have to worry about which circuit you're tapping. Say you want to add a drop outlet in the middle of the garage; simplest thing is to tap into the lighting circuit, but if you used 14 AWG you could be at the limit of your rating already. Just my opinion; worth exactly what you paid for it!

Good Luck!

c.

 

[TNToy]

Personally, I'd never pull 220 and 110 off of the same breaker the way cc_rider advised. Yikes. But alternating breakers at every other outlet is a good idea, and one I plan to use myself.

 

[Rrumbler]

Best practice calls for the fewest connections and the shortest runs between them.

In this case:
The two outlets should be separate from the lighting circuit; pull them off
of one or two of your outlet circuits.

I would make the "home run" from the panel to the switch (short distance)
then straight along one side of four boxes, and tap off across the joists
to the other four boxes. This way, you will only have one run on top of
the joists; the others can be fastened down along the side of them. The
distances involved in this layout are negligible; you may save five feet of
wire doing it one way, as opposed to another.

 

[the dude]

Ok, I have pulled the outlets off the lighting circuit and added two more outlets to run fans off of.

Remember this is only one circuit in my ceiling I was trying to figure out. I have two more circuits for other lighting. Code here would have let me run the plugs with the lights but it is going to be easier not to.

As for the walls. I have two duplex plugs going in every box on about five foot centers. Each wall will have two circuits and the each duplex plug in the box will be off a different circuit. All wiring will be 12 gauge with 20 amp breakers.

The question for the plugs:

Do I run two strands of 12/2 and have each plug completely independent or do I run one strand of 12/3 and share a common neutral on two circuits??

 

[Piper]

You could do either, I guess it just depends upon if you want independent circuits on each receptacle (ie: top plug 1 circuit, bottom plug a different circuit) or do you want 1 receptacle completely on 1 circuit leap frogging around the room. It it were me, I'd be running 12-2 to receptacle boxes 1, 3, 5 etc and 12-2 to receptacle boxes 2, 4, 6 etc. Using the 12-3 sounds good now but I'd suspect someone else looking at it to do alterations or updates thinking wtf?? The other thing is, with 2 strands of 12-2 you can easily connect receptacle to receptacle from the 2 hot screws and the 2 neutral screws on the receptacle. Using 12-3 you'd need to use marr connectors, more PITA stuff really.

My 2 cents

Piper

 

[the dude]

I want one plug on one circuit, with another plug, in the same box, on a different circuit. Do I need to run two 12/2 as shown with the orange as a neutral and the black as hot (ground not shown) or do I run 12/3 and use red as hot and black as hot with a common white neutral between plugs??

With my mad paint skilz:

 

[Charles (in GA)]

You can use three conductors, two hots, and one neutral (and the ground wire in addition to this). This is known as an Edison Multiwire Circuit and is legal and described in the code. However you Must use a breaker like that used on a 240v circuit, with a handle tie so that both trip at one time, and the two hots must be on opposing sides of the buss, just as a 240v circuit would be. The double pole handle tied circuit breaker will ensure you do this. All of this is possible because with the two hots on opposite busses in the panel (electrically) have opposite AC current cycles, and thus the neutral will also have opposing cycles, and won't overload. If you were to power both of the hots off of the same buss bar, then the neutral would overload. NEC 210.4 discusses multiwire circuits.

Charles

 

[cc_rider]

Yeah, what Charles said. I didn't explain myself well in the original post. I haven't done it myself but know it's a pretty easy way to run multiple circuits at the same time, and reduce the total amount of wiring without compromising safety. Since the two hots run off separate legs and separate breakers, they're effectively independent. And wiring 220 using this method might not be kosher, especially since many 220V devices require dedicated circuits anyway. A compressor or table saw or auto lift is gonna want its own circuit, and rightly so; their startup current is gonna cause problems for anything else on the circuit.

Attempting to remove foot from mouth,

chris

 

[fefarms]

Strictly speaking, the proposed multi-wire branch circuit wiring can be done with 12/3 and does not require a two pole breaker or even a handle tie. It is only when two receptacles are share the same yoke that the handle tie is required.

Since each individual yoke (duplex receptacle) connects to only one hot wire, the pair of yokes can share a neutral without the two pole breaker and be code legal. This is not necessarily an idiot proof arrangement, and it is a good idea to consider the two pole breaker or at least taping the pair of wires sharing the neutral together back at the panelboard (so you know to put them on different sides of the 240 volts).

As for me, I like the quad receptacle arrangement too, but I also like to have GFCI protection in my shop. So I run the multi-wire branch circuit to the first box, put in two GFCIs, then run two hots and two neutrals from there to the rest of the string of receptacles.