Electrical Circuits in a Workshop

Question

I am doing some renovation in my workshop and am considering doing something kind of unusual. I find that I am always looking for outlets to plug in tools, lights, etc. Rather than using power strips, I'm thinking of installing a bunch of outlets instead. On the wall where my workbench will be, I plan to install 8 outlets (one on each stud). Here's the unusual part: I want to make sure I don't overload the circuit, so I plan to put those 8 outlets on two separate circuits in an alternating pattern (i.e. outlet #1 on circuit 1, outlet #2 circuit 2, outlet #3 circuit 1, outlet 4 circuit 2, etc..). My shop has exposed studs and 4 existing 20 amp circuits. I would be adding 4 outlets to two existing circuits. I am comfortable with this kind of work, but will also have my work inspected according to my local codes.

So my question is, is my plan reasonable or a crazy. Your input would be really helpful. I'd rather the internet tell me that I'm an idiot than an inspector. :-)

Thanks for your time, and please let me know if I can provide any additional information.

Answer 1

A multiwire branch circuit would work well for this. You'll install a double pole 20 ampere breaker, or two 20 ampere breakers with the handles tied together. Then you'll pull 12/3 with ground cable from the panel, to the first box. And 12/3 with ground cable between each box.

In the panel

In the panel you'll connect the black conductor to one of the breaker terminals, and the red conductor to the other breaker terminal. You'll connect the white conductor to the neutral bar, and the bare ground to the grounding bar.

At the first box:

• Connect the black wire from the feeder cable to the brass colored screw on the receptacle.
• Connect the black wire from the cable leading to the next box, to the other brass terminal.
• Connect the red wires together.
• Connect the white wires together and include a short bit of scrap wire for a pigtail.
• Connect the white pigtail wire to a silver screw terminal on the receptacle.
• Connect the grounding wires together and include a short bit of scrap wire for a pigtail.
• Connect the grounding pigtail to the green screw on the receptacle.
• If it's a metal box, include an additional grounding pigtail, and connect it to the box using a grounding screw or clamp.

At the next box:

Follow the same procedure as above, but connect the red wires to the receptacle instead and let the black wires "pass through".

Continue the pattern.

Now simply continue the pattern, connecting black wires in one box and red in the next.

GFCI protection

Since the receptacles are in a garage, they'll likely have to be GFCI protected. You can accomplish this by using a GFCI breaker, or installing a GFCI receptacle as the first receptacle on each line (two total).

However, using receptacles is a bit more complicated, since the grounded (neutral) conductor cannot be shared with GFCI devices. This answer explains how to wire multiwire branch circuits with two GFCI receptacles.

AFCI protection

Arc-fault protection may also be required, which is commonly provided by installing an AFCI breaker.

Dual protection

If both types of protection are required, you'll likely end up with an AFCI breaker and GFCI receptacles. Breakers that provide both GFCI and AFCI protection are available, but can be difficult to find and may be expensive.

If you can't find a dual function circuit breaker, and you have to use separate GFCI receptacles on an AFCI protected circuit. You can use a combination of 12/3, and 12/2/2 cables. 12/2/2 cable contains two ungrounded (hot) conductors (black, red), two grounded (neutral) conductors (white, white with red stripe), and an equipment grounding conductor (bare copper). You'll wire the circuit like this.

^{Pay close attention to the wiring of the grounded (neutral) conductor at the first GFCI, as to avoid sharing the grounded (neutral) between GFCIs.}

In a scenario like this, you could break the tabs on both sides of the receptacles, and feed the top and bottom of the receptacles with separate circuits. For example, all the bottom plugs could be circuit1, while all the top are circuit2. This would be wired like this.

Protection from physical damage

Since this is in a garage, and you said the stud bays are open. You might be required to protect the cables from physical damage. This can be accomplished with conduit, running boards, installing drywall, or closely following the structural members. For example, if you have a nonmetallic cable running from one stud to another. You can:

• Run the cable through conduit.
• Install a running board between the studs, and route the cable behind it.
• Install drywall to cover the entire wall, or just the portion of the wall where the wiring is.
• Run the cable up the stud, through the top plate(s), then down the other stud. Making sure the cable closely follows the studs, and is secured properly to the studs.

Answer 2

Sure, it sounds overboard to me, but I don't know your needs or what you will be doing with all those outlets.

Will you be using several power hungry tools at one time in your shop? If so, it makes sense to split up the outlets on multiple circuits.

Are those power hungry tools located directly next to each other, where having the alternating pattern you've suggested necessary? If so, maybe it's not that crazy.

Do you need to have every tool plugged in at the same time, necessitating an ungodly amount of receptacles? If so, then you have your answer!

An outlet every stud sure would be interesting to see, please share some photos!

Answer 3

I am a big fan of a lot of plugs. I always think its a great idea.

I understand that you are going to add 4 receptacle (plugs) to an existing 20A circuit. And 4 more plugs to another existing circuit. It would be nice to know how many devices or lights or big loads (table saw plugged into one of the plugs?). That way we can assess if your circuit would be overloaded. There seems to be discussion on how many plugs/devices to be on a circuit. Maybe your location would also help somebody answer better with that information.

The way you feed your plugs will be important to. You cannot have multiple circuits in one box unless it's on a two pole breaker (i.e. split receptacles where the top of the plug is one circuit and the bottom is another on a two pole breaker or 2 breakers tied together) So just be mindful of that when you are wiring the circuits up.

A lot of electricians also purchase 4by4 boxes and put two receptacle in it side by side. They are nice at a battery charging station. Where you have a lot of little loads...

Answer 4

I think every stud is too close. I would put in a double outlet every other stud, and put one outlet on each circuit.

And if you want that many outlets, go ahead.

Oh, and some jurisdictions let you schedule a pre-construction ("pre-con") inspection, where the inspector comes out, you tell them what you want to do, and they tell you what you are looking for.

Note that since these are in a garage they will need to be GFI protected, but you can use separate GFIs at the beginning of the run and chain later ones onto the load terminals of the GFI.

Answer 5

I'm a fan of using quad boxes on every 3rd stud (every 4 feet). My charging station is one of those long metal mountable power strips.

I don't like having circuits on different legs next to each other. 220v potential is possible. (Like say stacked stereo components.)

I also wire lights on separate circuits so my tool doesn't kill the lights if it pops a breaker.

I prefer to use unprotected circuits (no gfci etc) even in garages for things like door openers and freezers where a circuit interrupt can be inconvenient.