quick electrical question

[Russ Ambrose]

getting ready to wire the new shop and have a quick (hopefully) question. i understand that 10-3 wire is generally used to facilitate a 30 amp circuit, but is there any reason (code or safety) that i couldn't run 10-3 wire but instead use a 20 amp breaker and 20 amp plug? i only need 20 amp circuits for my current equipment, but would like to (if possible) run 10-3 in case i later get equipment that requires a 30 amp circuit (at which point i would replace the breaker and plug accordingly). thanks.

[Mike Hollingsworth]

No Problem

[Mike Henderson]

I agree - no problem. Except that 10 gauge wire is a bit hard to handle (bend, stuff back into a box, etc.).

Mike

[Phil Thien]

The only possible issue is that you should make sure your receptacles and plugs are designed to accommodate 10. If those items state a maximum wire size of 12, then you shouldn't use 10. I've always wondered whether it would be okay to pigtail off a 10 to some 12 in order to connect to receptacle (for example). I've been told doing so would be a gray area.

[Mike Heidrick]

10-3 romex is 3 conductors and a ground. You only need 10-2 for a 240v 1phase - two conductors for hots and a ground. Some guys use 10-3 if they want to use the same run for 120V too as the 3rd conductor is used as the neutral.

[Rollie Meyers]

10-3 romex is 3 conductors and a ground. You only need 10-2 for a 240v 1phase - two conductors for hots and a ground. Some guys use 10-3 if they want to use the same run for 120V too as the 3rd conductor is used as the neutral.

You cannot tap a 15 or 20A receptacle or circuit off a 30A circuit, some type of overcurrent protection is required...

[Mike Heidrick]

You cannot tap a 15 or 20A receptacle or circuit off a 30A circuit, some type of overcurrent protection is required...

I am not a fan of using 10-3 for anything other than 3 phase lines. Personally I run all seperate 240V and 120V lines.

It may not be code or recommended/safe but you can do it and the tools will work perfectly.

[Rollie Meyers]

I am not a fan of using 10-3 for anything other than 3 phase lines. Personally I run all seperate 240V and 120V lines.

It may not be code or recommended/safe but you can do it and the tools will work perfectly.

And it unwise to do non code compliant or unsafe work, it works to replace fuses with copper pipe but is not prudent to do so, just because one can, does not mean they should.

[Steve Meliza]

is there any reason (code or safety) that i couldn't run 10-3 wire but instead use a 20 amp breaker and 20 amp plug? i only need 20 amp circuits for my current equipment

There is no code or safety reason why you can't use #10 wire as you describe.

The purpose of the breaker per NEC definition is to protect the wire from over current. The ampacity rating of wire is its maximum, there is no minimum rating. I do agree that you must make sure to use outlets rated for #10 wire connections or pigtail with #12. You'll just need to remove or replace those pigtails if you ever up the circuit to 30A.

The breakers and outlets are required by NEC to have the same rating except when you have a 20A breaker you can use 15A or 20A rated outlets.

[Prashun Patel]

As said, 10-3 will be harder to handle than 12-3 or 12-2.

If you ever upgrade, it will likely be to handle 220v tools. In this case, the current draw will actually be less than 110v for the same amount of power. 12-2 will be plenty for a 20A 220v circuit to handle a single power tool at a time.

[Chris Padilla]

I ran #10 throughout my garage but I ran it in conduit and used STRANDED #10. I didn't feel like buying separate spools and colors of #10 and #12 so it was all #10. Now this was a good 7-8 years ago when copper was a lot cheaper.

[Kent A Bathurst]

Oversize the wire, with respect to the breaker, is OK.

The breaker keeps the wire from meltdown.

Then, as you say, you can ^^ breaker to 30a in the future if you want. All good.

Going the other way is verboten - ie, oversize the breaker for the wire guage. A 30a breaker on 20a wire is how houses burn down.

[Anthony Whitesell]

You cannot tap a 15 or 20A receptacle or circuit off a 30A circuit, some type of overcurrent protection is required...

True. As the OP states, he would like to put in 20A breaker, 10g wire and 20A outlets. That would be fine. The gotcha will come when the 20A breaker is changed to a 30A breaker, then all the outlets will need to be upgraded as well. Which will very likely make the original outlets useless as 15/20A outlets are very different in the plug configuration from the 30A outlets.

[Rod Sheridan]

getting ready to wire the new shop and have a quick (hopefully) question. i understand that 10-3 wire is generally used to facilitate a 30 amp circuit, but is there any reason (code or safety) that i couldn't run 10-3 wire but instead use a 20 amp breaker and 20 amp plug? i only need 20 amp circuits for my current equipment, but would like to (if possible) run 10-3 in case i later get equipment that requires a 30 amp circuit (at which point i would replace the breaker and plug accordingly). thanks.

The other option is to buy machinery with better quality motors.

A high efficiency, high power factor motor will not require as large a feeder.

Now, that's a somewhat tongue in cheek answer, however it's factual.

A good 3 hp motor will run from a 15 ampere circuit at 240 volts, a 20 ampere circuit will be plenty large enough for a home shop.

A 20 ampere multi-wire branch circuit will runn all your 240 volt and 120 volt machines with one breaker and one feeder............Rod.

[Rollie Meyers]

I ran #10 throughout my garage but I ran it in conduit and used STRANDED #10. I didn't feel like buying separate spools and colors of #10 and #12 so it was all #10. Now this was a good 7-8 years ago when copper was a lot cheaper.

If you needed green or white colors, you violated code by remarking them, 6 AWG and smaller is not allowed to be re-identified as grounding, or grounded (neutral) conductors. See 250.119(A), & 200.6(A)