Adding a New Garage Circuit

[eljefino]

Well... I heard the opposite, that "skin effect" favors stranded wire. But it's not that big a deal at 60Hz.

OTOH, when you put an extension cord on an outlet, you've added more length of wire, and another connection, both of which are slightly detrimental.

I've run my air compressor (regular cheapie 1.5 hp) on a 16 gauge extension cord and it was not happy at all, slow to start, smelling hot. Put it on the 12 ga yellow jacket and it purred like it was plugged into the wall.

I would absolutely wire for 20 amp/ 12 ga. It'll keep the lights from dimming as badly when you start up a tool.

[Ferrino]

Originally Posted by pattenp

It's okay by NEC to use 15A receptacles on a 20A circuit. There's no need to buy the actual 20A receptacles that have the T shaped slot on one side.

Why is this the case? Is it because a device that has the 15A 3-pin plug will never draw more than 15A and will therefore never exceed the rated limit of the 15A outlet?

In that case, the only advantage of having a 20A circuit over a 15A circuit is when you have multiple devices running, yes?

[Alchymist]

Originally Posted by Ferrino

Why is this the case? Is it because a device that has the 15A 3-pin plug will never draw more than 15A and will therefore never exceed the rated limit of the 15A outlet?

In that case, the only advantage of having a 20A circuit over a 15A circuit is when you have multiple devices running, yes?

The other advantage of the 20 amp circuit is for motor starting- power tools that don't draw more than 15 amps sometimes have a much higher starting current. (Think circular saw, table saw, etc).

[FluxCore]

Gooberheads, we select 20A outlets and plugs because they are higher quality construction and will offer less resistance to whole circuit. So what if you seldom need it's full capacity?...It's there when you do need it, plus it survives longer in shop use compared to bedroom alarm clock use.

Would you enjoy it when you plug in ANYTHING and the cord falls out of the outlet?...Been there, done that.

If you are wiring your shop, not a yuppy garage, but a shop, then use only 12/2 and industrial or hospital grade outlets....If any of your shop tools offer 120/240, then switch them to 240 and wire outlets for them with at least 10AWG.

A SHOP is populated by MEN that use POWER TOOLS and have STIFF electrical with TIGHT recepticals.

If your shop lights dim when you flip something 'on', you need to upgrade or stay in front of the tube.

Just sayin

[pattenp]

Basically yes to your questions. To add, NEC requires there to be more than one outlet if using 15A outlets on a 20A circuit. If there is only one outlet then it has to be a 20A. Also if using 15A outlets on a 20A circuit it's best not to daisy chain them using the side connectors, it's best to use pigtails. Actually it's best to use pigtails when connecting outlets, 15A or 20A. IMHO

Originally Posted by Ferrino

Why is this the case? Is it because a device that has the 15A 3-pin plug will never draw more than 15A and will therefore never exceed the rated limit of the 15A outlet?

In that case, the only advantage of having a 20A circuit over a 15A circuit is when you have multiple devices running, yes?

[Ferrino]

Thanks very much - that's a lot clearer now. I assume a 15A GFCI outlet is OK to use on a 20A circuit too?

Although I don't understand why a single 15A outlet on a 20A circuit is an issue? This is just a curiosity for me, as all of my circuits will have a minimum of 2-3 outlets.

Yes, I would always plan to join wires within a wiring plug instead of at the side-connector screw.

[Alchymist]

Originally Posted by pattenp

Basically yes to your questions. To add, NEC requires there to be more than one outlet if using 15A outlets on a 20A circuit. If there is only one outlet then it has to be a 20A. Also if using 15A outlets on a 20A circuit it's best not to daisy chain them using the side connectors, it's best to use pigtails. Actually it's best to use pigtails when connecting outlets, 15A or 20A. IMHO

I may be remembering wrong, and I'm sure someone will correct me if I am, but, as I recall the 15 amp DUPLEX outlet is considered two outlets for that purpose. The restriction is on the "15 amp single" outlet.

[pattenp]

My understanding is the same as yours. I did mean a single outlet not a duplex. Good you gave that clarification.

Originally Posted by Alchymist

I may be remembering wrong, and I'm sure someone will correct me if I am, but, as I recall the 15 amp DUPLEX outlet is considered two outlets for that purpose. The restriction is on the "15 amp single" outlet.

[Dick in Wisconsin]

Originally Posted by FluxCore

Gooberheads, we select 20A outlets and plugs because they are higher quality construction and will offer less resistance to whole circuit. So what if you seldom need it's full capacity?...It's there when you do need it, plus it survives longer in shop use compared to bedroom alarm clock use.

Would you enjoy it when you plug in ANYTHING and the cord falls out of the outlet?...Been there, done that.

If you are wiring your shop, not a yuppy garage, but a shop, then use only 12/2 and industrial or hospital grade outlets....If any of your shop tools offer 120/240, then switch them to 240 and wire outlets for them with at least 10AWG.

A SHOP is populated by MEN that use POWER TOOLS and have STIFF electrical with TIGHT recepticals.

If your shop lights dim when you flip something 'on', you need to upgrade or stay in front of the tube.

Just sayin

This is really good advice.

With the amount of wire you're running and few number of outlets and breakers, wire everything for 20amp and don't worry about it. The suggestion to run 12/3 wire to the workbench and have one circuit for tools and one circuit (separate breakers) for lights is a good one. Pop the tool breaker, and you still have lights, the radio should work, and the digital clock won't reset.

When you wire the outlets, put two duplex outlets in double gang or triple gang boxes; that way you'll reduce the need for power strips. If you use triple, put the outlets at the ends so you have room for more than one wall wart transformer for your cordless stuff and your phone. Put the light switch in the middle if appropriate, or leave it blank.

Wiring 15amp outlets is only nickle and diming yourself to death. Remember what the guy above said about buying quality, heavy duty outlets. You pay for what you get. You're not going to be plugging in a bunch of lamps with 13w CFL bulbs. Your tools will run better on the 20amp circuits too versus being on the "edge" of the circuit every they lug down in heavy going like an oak 6x6 or drilling a 1" hole in thick steel.

[Ferrino]

I thought I read somewhere that outlets must be placed at a minimum distance above concrete floors in a garage?

Originally Posted by acer66

I do not think there are any real rules about the placement of receptacles besides some, I think, when it come to access for disabled people but I don`t think this applies to you.

In general a lot of people will mount the upper receptacles higher than 48" to be able to lean sheet good against the wall and still be able to access the receptacle/switch.

At your workbench I would just mount them where they are the most convenient for you.

It does not matter how far away the old work boxes are placed away from the studs assuming the framing is done somewhat right and you do not have 1/4" drywall on the walls.

If you do not know what is going on in your walls, existing ducting, cables, water lines, etc.
be careful when you start cutting the holes.

You might also have a fire stop right where you want to place your box.

[acer66]

I think there is one regarding garage outlets needing to be 18" off the floor due to the sparks igniting vapors but I think that only applies to commercial structures.