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-   -   12 AWG circuit, Breaker 15A, 20A or either? (http://www.diychatroom.com/f18/12-awg-circuit-breaker-15a-20a-either-45288/)

SteveG 05-26-2009 12:34 PM

12 AWG circuit, Breaker 15A, 20A or either?
 
I have run a circuit for deck lighting and receptacles. I used 50 ft of 12-2 from the panel to the first receptacle on outside wall, and will change to 12 AWG THWN to go to other destinations on deck (may be up to 50 more feet of wire to termination of run) I chose 12 instead of 14 mainly because of the run length.

Should I call this a 15A circuit because of the length of the run and voltage loss?

Or call it a 20A circuit and use a 20A breaker? The advantage here is that it may be less likely to trip when using power tools

Pros/Cons/Pertinent Code Requirements?

I've been told to use regular 15A GFCI receptacles and switches in either case because they are actually rated for 20A circuits...is that correct?

Gigs 05-26-2009 12:38 PM

You can make it 20 amp, if the voltage drops, it will drop on a 15 amp breaker too. A 15 amp breaker will run at 20 amps for a very long time... can be hours. So just make it 20 amps.

And yes it is normal to use 15 amp GFCI and outlet on 20 amp circuits. Only make devices 20 amp if you need 20 amp.

TheTuna 05-26-2009 12:46 PM

Quote:

Originally Posted by SteveG (Post 278713)
I've been told to use regular 15A GFCI receptacles and switches in either case because they are actually rated for 20A circuits...is that correct?

Just to clarify things a little, the receptacles are rated for 20A "Pass Through"
What that means is that they can be used on a 20A branch circuit, but the receptacle itself is rated for delivering 15A to the device connected to it (from the front).

SteveG 05-26-2009 01:05 PM

Quote:

Originally Posted by TheTuna (Post 278718)
Just to clarify things a little, the receptacles are rated for 20A "Pass Through"
What that means is that they can be used on a 20A branch circuit, but the receptacle itself is rated for delivering 15A to the device connected to it (from the front).

AHHH, so what happens if you plug in a motor that exceeds the 15A rating?

I'm guessing that on a 15A circuit, the breaker will flip
But if it is on a 20A circuit will the receptacle melt?

If so, would that be a reason to use a 15A breaker, OR install a 20A receptacle where high amp motors may be used?

Gigs 05-26-2009 01:12 PM

Quote:

Originally Posted by SteveG (Post 278729)
AHHH, so what happens if you plug in a motor that exceeds the 15A rating?

I'm guessing that on a 15A circuit, the breaker will flip
But if it is on a 20A circuit will the receptacle melt?

If so, would that be a reason to use a 15A breaker, OR install a 20A receptacle where high amp motors may be used?

No. A motor should not draw 20 amps (for any sustained period of time) with a 15 amp plug on the end of the cord.

If it does because it's faulty, then the outlet will be fine as well. It's not like it will melt at 20 amps when it's fine at 15 amps. Eventually, if it were operated that way for years the plastic might get brittle or scorched and the wire insulation might get damaged. More likely, everything would be fine.

J. V. 05-26-2009 01:34 PM

Quote:

Originally Posted by SteveG (Post 278729)
AHHH, so what happens if you plug in a motor that exceeds the 15A rating?

I'm guessing that on a 15A circuit, the breaker will flip
But if it is on a 20A circuit will the receptacle melt?

If so, would that be a reason to use a 15A breaker, OR install a 20A receptacle where high amp motors may be used?

Breakers trip on overload or short circuits. Receptacles melt due to bad connections or misuse.

If the OP is going to be running large motors on this circuit, then the whole concept of this thread needs to be changed. We cannot advise on what we do not know or what the OP plans to plug into the receptacles.
He asked about 15 and 20 amp circuits and that what we are making suggestions on.

SteveG 05-26-2009 09:21 PM

This circuit is intended for deck lighting and receptacles, grill, leaf blower, etc. The reason I was asking about the motors was to further understand the consequences of the 15/20A decision for this circuit, or any other I may wire in the future. I may be using the circuit to plug in power tools while building the deck, most particularly a table saw that sometimes trips the breaker in my 15A garage circuit....I wondered if using a 20A breaker vs. 15A breaker and 20A recep vs 15A recep would make a difference.

Daniel Holzman 05-26-2009 09:32 PM

The cost difference between a 20 amp receptacle and a 15 amp receptacle is only a few dollars, ditto for a 20 amp rated GFI vs a 20 amp passthrough/15 amp direct GFI. In my house, I use all 20A outlets and GFI's, and I wire my runs with 12 gauge wire and use a 20A breaker. Gives me a bit more flexibility in what I plug in. However, some would argue that the extra cost is a waste.

Scuba_Dave 05-26-2009 09:33 PM

Breakers are about the same price - I'd use a 20a
A tool that requires 20a will have a 20a plug & require a 20a outlet
I've yet to own one

micromind 05-26-2009 09:44 PM

If you take just about any 15 amp receptacle apart, you'll find the inside is exactly the same as a 20 amp. The only difference is the face.

This is the main reason why code allows 15 amp receptacles to be connected to 20 amp circuits.

A 15 amp receptacle in good condition connected to a gradually increasing load will cause a 20 amp breaker to trip long before any overheating will occur.

If it were my installation, I'd use a 20 amp breaker for #12. To use a 15 will be confusing to anyone else who might work on the system later.

Rob

spark plug 05-26-2009 09:59 PM

Now you're hitting the [proverbial] nail on the [real] head...! This is the reasoning of the NYC Electrical Code. (Before they joined the NEC, in 2005)! That a lighting, or "Mixed Use" Branch circuit would ALWAYS have to be protected by a 15amp. breaker. (Regardless of the wire size; #14awg. is not legal to use in NYC, anyway) A 20amp. Branch Circuit would only permit Two Receptacles on it, and NO lighting loads!!!

J. V. 05-27-2009 12:05 PM

Use a 20 amp breaker on the circuit then. You already know that a 20 will run a larger load than a 15. You have the right size wire for it.


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