Number of circuits?

[Karl Fields]

Starting on the wiring of my 36x48 garage. Lights are all in and now on to 120v receptacles!

Question is I am not sure how many circuits to allocate for this. The walls are on the 48' sides while the 36' ends are almost all doors. I am thinking of running two 20A circuits down one wall and alternating the receptacles between the two circuits. Probably 8 to 10 receptacles on the wall.

Then doing the same with two more 20A circuits on the opposing 48' wall. A couple of receptacles on the end walls tied into one of the above circuits.

Good plan? Flawed plan? Suggestions?

 

[porschedude996TT]

I think you have a good plan. It all depends on what you are doing and how many people will be working.

I have two 120 volt receptacle circuits in my 30' x 40'. It has been good for some time but I ran into a problem the other day. My Miller MIG welder is rated at 20amp. So is the receptacle breaker. If I short out the wire coming from the welder gun, it will trip the breaker or if I weld too long it does it as well.

First I thought it was because I have the surround sound and TV on and had the welder plugged into the same circuit. I moved it to the other side of the shop which is a different circuit and it was better.

When I planned the shop I wired in a 240v 30 amp receptacle with a neutral. This way I could make a pig-tail with a 20 amp receptacle and be able to put a better than 20amp load on it. By wiring it for both voltages I am able to eliminate the tripping breaker.

I have 13 duplex receptacles on each of the two 20amp circuits. These are convenience outlets…

I also oversized the wire (#10) to reduce any voltage drop.

 

[pattenp]

To have alternate outlets down the same wall to be on separate circuits you may want to consider running a multiwire branch circuit using one run of 12/3 vs running 2 runs of 12/2. The two circuits will need to be on 2 single pole breakers with a handle tie or a standard double pole breaker. This should save you a little money on wire.

 

[Highbeam]

To have alternate outlets down the same wall to be on separate circuits you may want to consider running a multiwire branch circuit using one run of 12/3 vs running 2 runs of 12/2. The two circuits will need to be on 2 single pole breakers with a handle tie or a standard double pole breaker. This should save you a little money on wire.

Doesn't that, MWBC, make GFCI protection difficult? How do you do it?

 

[pattenp]

That's a good point about the GFCI. Putting a GFCI outlet in the first outlet on a MWBC is problematic. You could use GFI breakers but there goes any savings on the wire. Forget my MWBC suggestion.

 

[Spudland_Dave]

When I was "Sketching" my wiring diagram in my head I thought about doing the alternating thing...between wire costs & speaking with various electricians about it, came to the conclusion its one of those things that sounds great but out in the real world isnt so hot.
Make it easy on yourself, just use more circuits with less outlets...Put bigger stuff like compressors/welders/etc on dedicated outlets and dont lose sleep over it.

 

[tylernt]

When I planned the shop I wired in a 240v 30 amp receptacle with a neutral. This way I could make a pig-tail with a 20 amp receptacle and be able to put a better than 20amp load on it.

20A receptacle on 30A breaker... even with 10ga wire, is that legal?

 

[pattenp]

Nope, 20A outlet on a 30A circuit is not to code. porschedude996TT didn't say the circuit was on a 30A breaker, but you'd think it is since he has a 30A outlet on it.

20A receptacle on 30A breaker... even with 10ga wire, is that legal?