I am doing a remodel of my master bathroom. I had to move a box on the wall and realized the wire was 14-2 on a 15 amp circuit (it was installed around 1987 and don’t know what the code demanded). This wire supplies both the lights and a GFI. I know today’s code calls for 20 Amp with 12-2.
I am running a new 12-2, 20Amp circuit to supply the GFI. The GFI will supply and protect the in shower fan/light..
My question is this: Does the wiring that leaves the GFI need to be 12-2? This wire will only supply the fan/light. I am thinking that it would be OK because the 12-2 would service the GFI which onlys allow the wife to plug in hair dryer. Thank you.
Replies
In general (there are exceptions), all the wire in a circuit must be large enough to be "protected" by the breaker. If it's a 20 amp breaker this means all wire must be #12.
Does the wiring that leaves the GFI need to be 12-2?
YES, ABSOLUTELY
ALL the wire of a circuit protected by a 20 amp breaker MUST be 12ga. minimum, Similarly, ALL the wire of a circuit protected by a 15amp breaker MUST be 14ga.minimum
There was no reason to change from the 14ga. to 12ga, the existing was more than sufficient for the demand on that circuit.
The only "up-grade" would be that the outlet be a GFCI protected outlet if it were not already, otherwise you wasted your time upgrading to a 20amp circuit.
Geoff
Note that one can use a 15A breaker on #12 wiring. If you do this though, with some #14 "downstream", you should label the wire at the breaker panel to indicate that there's #14 downstream (so someone else doesn't come along later and "upgrade" the breaker).
(Sometimes people get confused about the current requirements of outlets. An outlet labeled "20A" on the back does not have to be in a 20A circuit. Only if the outlet has one T-shaped slot, indicating that it accepts 20-amp plugs, does it need to be on a 20A circuit.)
"mixing" of wires on cicuit
Dan, my understanding of the code is that you can NOT mix wire gauges on a circuit.
As to outlets, the rating on the outlet is the max load (amperage) that that unit can be used for. But the circuit breaker is the
controlling factor for load capacity on the circuit.
I agree on the "T" slot outlets being required to be on a 20amp circuit.
Geoff
Yeah, I think the code hems and haws a bit re mixed gauges in a circuit. It's certainly discouraged, for the reason I gave -- someone might assume the entire circuit is the gauge they can see at one point and hence "protect" the circuit with an inappropriately large breaker.
We're Not Plumbers
Plumbers often reduce pipe size as the line progresses from fixture to fixture. Electricians don't do that. Wires, for the entire circuit, are sized according to the size of the circuit breaker. Period. It matters not that the circuit 'only' powers a 3-watt LED light, or your table saw or your air conditioner.
There is never a (code) problem with using a larger size wire. Indeed, the various tables in the codebook are frequently misunderstood, and used incorrectly- but that's a topic for another day. I often encounter jobs where the customer has specified 'oversize' wire, at least for the first part of the circuit. Not a problem.
That said .... STOP REINVENTING THE WHEEL. Schools really set us back a few centuries when that came out with all this self-esteem 'you're smart enough to figure things out' silliness. Trades are called "Skilled trades" for a reason. You can't learn them by reading a book, and it takes more than a few days to master them.
Often overlooked is the introduction to the code - which plainly states you're supposed to know the trade BEFORE you try to apply the code. It is NOT an instruction book, a design guide, or anything else.