How Many Circuits?

[BQuicksilver]

Well, we're rewiring the old 20x20 attached garage I was curious as to how many dedicated 20A circuits we should run? We are planning to run a 220 for compressor and will not be welding in this garage.

Of course the more outlets the better, but i'm trying to think as to why (what uses) might bring me to wish we had more circuits out there in the future.

 

[RonBou]

I put 7 circuits in my 24x24 garage. Most were 15A for lights and 3 20A for my 110V 2 stage compressor and 2 "just in case" circuits.

 

[T1704]

I have 7 recepts of off two 20A circuits. (26x20 garage) Wish I would have added two more circuits (20A) and probably 3-4 more recepts, then evenly divided the recepts.

You will never say...damn...I wish I wouldn't have added that extra one, but it sure ***** when you need an extra one.

 

[Ign]

I think it largely depends upon how many people you think will be working in the garage at once. If usually just 1 to 2, you probably don't need that many circuits since you're not likely to have more than one or two power tools going at once.

But DO consider constant but "invisible" loads, like cordless battery chargers, fridge, TV, stereo. If you have all this on a circuit it's possible a chop saw would push it over the edge.

I've had good luck doing one circuit per wall, it makes wiring easy and troubleshooting or maintenance easy later on. If I'm tripping a breaker on one wall I just plug one item into the next adjacent wall, but I almost never trip 20A breakers. Others prefer to alternate outlets such that every other box is on a different circuit. There's a lot of validity to this approach if you want to put the time into it. In a shop that's only 20x20 you probably don't need to do this.

I'd put your lights on their own circuit. The only 15A circuits I ran were for my lights or ceiling fans. All my wall receptacles are 20A.

And I agree w T1704, the cost of adding more receps now is negligible. If you put any value on your time having to juggle plugs is a PITA.

 

[boiler7904]

Ign gave some good advice. Don't forget about all of the little stuff that'll always be running.

I have a 19 x 22 garage that i'll be wiring in the spring or early summer. Current plan is:

(1) 15A for lighting
(1) 20A for portable compressor
(4) 20A for general purpose receptacles - 1 circuit per wall with 1 duplex eceptacle every 5' or so along each wall. There will be a receptacle on each side of the overhead door for running a shop vac in the driveway or christmas lights outside.

 

[byrdman]

Sounds like you're planning about right. I did the alternating circuits thing, just in case I found later that I wanted to plug everything in all in one area I wouldn't overload one circuit. My shop is 28x35, I did 4 20A circuits for lighting (2 inside, 1 in attic, 1 outside for floods.) I went with 20A just in case I decided I wanted to plug tools into my lighting circuit (shop lights plugged into receptacles). I did 4 20A receptacle circuits, quad outlets every 4'. The extra outlets are also handy because later on, you'll probably cover some of them up with various stuff. One power cord reel mounted to the ceiling in a central location is a very useful thing to have, it sorta functions as a receptacle for many locations. You might plan for one of those?

 

[ZRX61]

I have:
220v/20a Comp
220v/20a Radial Arm Saw
220v/20a 8in Planer/Jointer & Tablesaw
220v/40a Welder (2 outlets 30ft apart)
220v/15a Plasma Cutter (2 outlets 30ft apart)
110v/20a 2 quad receptacle (will have 2 more quads added in future)
110v/20a 2 quad receptacle (will have 2 more quads added in future
110v/20a 3 quad receptacle (will have 1 more quad added in future)
110v/15a lights & GDO.

seems to work ok

 

[rbcsaver]

My Bro-in-law had an excellent idea, when running outlets run a single 20A circuit, to each series (number your choice depending upon use) of upper outlets, then a separate line for the lowers. Snap out the tabs to keep them isolated. Thus if you have some cahrgers plugged into the upper outlet and your chop saw on the lower, then there is separate line draws. My lights will be 15A, but all the outets will be 20A in my 30x40 garage.
I ran the 100 amp subpanel-service from the house. Remember, that if this is your plan also, there must be a 100 amp breaker at the main box and the subpanel must have separate ground rods and the neutrals/grounds must be isolated. Check and re-check your local codes.
regards,
Steve

 

[thefairlaneman]

In my 21x31 garage I ran 2 for the lights, 3 for the wall outlets and 2 separate 220 circuits,one for a compressor and the other a wall outlet for my welder. Seems to be plenty

 

[russlaferrera]

On a different note, I would like to mention "location" I have found that a 220v 50A box located near the overhead door is great for welding projects outside on nice days and in 1/2 way and at the front of the garage. Also some outside 120v boxes around the perimeter for drop lites, battery chargers and stuff...russ

 

[thefairlaneman]

ress, yes I also put my 220 plug in under the main panel located at the front . Its better to weld outside when possible.

 

[Charles (in GA)]

My Bro-in-law had an excellent idea, when running outlets run a single 20A circuit, to each series (number your choice depending upon use) of upper outlets, then a separate line for the lowers. Snap out the tabs to keep them isolated. Thus if you have some cahrgers plugged into the upper outlet and your chop saw on the lower, then there is separate line draws.

While this is a good idea, and you are even allowed to share a single neutral line to the two of them if the two hots are absolutely, positively, on opposite hot buss bars (240 volt potential between the two hots) (remember, the two hots are opposite phases so the alternating cycles on the neutral doesn't overload it)
you MUST also use a two pole breaker with a tie bar between the handles (like you use on a 240 circuit).

Other words of learned wisdom. Spend the money and buy good quality screw tighten backwire outlets. These are the ones that you loosen the screw, push it it all the way, insert the straight wire, and tighen up the screw. This pinches the wire with a serrated plate inside that is tighened by the screw. Very positive and effective. Leviton Pro Grade has a back wire model, and so does Eagle/Cooper. They have very stiff contact springs inside and are quite difficult to plug into and pull plugs from, what you want in a shop. They are also very good quality inside having the same guts as the 20 amp rated receptacles (same unit different faceplate)

Also, for commercial purposes you can have no more than 10 receptacles on a 15 amp breaker and no more than 13 on a 20 amp breaker. This would be a good rule to follow, however most people would never put that many on one breaker anyhow. I have 27 receptacles on nine breakers. A couple of circuits have 4 receptacles and a couple of circuits have only one receptacle (a single 20 amp rated outlet for super heavy duty 120V work such as Mig welders.) I did 4 inch square deep boxes with two receptacles in each, on opposite phase circuit breakers. Used metal fronts with three screws retaining each receptacle (top, bottom and center) into the stamped cover. Very solid.

Charles

 

[ultgar]

I agree with Charles...its not much more to buy a better quality receptacle. I keep a few on hand for projects around the house and garage and personally like the Pass & Seymour 5362A and 6300 series....

See http://www.passandseymour.com/products/product.html?s=91&mkt=4 for details.

And forget about the cryo treated ones for sale on the web....your tools won't know the difference. SD