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I have a half bathroom I was going to power with a dedicated 20 amp circuit breaker.

I was going to use the 20 amp breaker to power:

  • vanity light
  • shelf light (Phillips hue light strip)
  • outlet
  • bathroom fan

I was curious if this is frowned upon or even allowed? More specifically if using 12-2 to power my vanity light, and light strips is unsafe or “too much power”

I was under the impression 14-2 is typically used to power these sort of things so I was unsure what is preferable and safe.

Any help would be appreciated

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You must use 12AWG with a 20A breaker for this run

Your "half-bath" is still a bathroom by the NEC's definition, as it has a toilet and a basin aka sink:

Bathroom. An area including a basin with one or more of the following: a toilet, a urinal, a tub, a shower, a bidet, or similar plumbing fixtures.

As a result, the fact you have a receptacle on this circuit makes it a bathroom branch circuit, which falls under NEC 210.11(C)(3) and the Exception thereto:

(3) Bathroom Branch Circuits. In addition to the number of branch circuits required by other parts of this section, at least one 120-volt, 20-ampere branch circuit shall be provided to supply the bathroom(s) receptacle outlet(s). Such circuits shall have no other outlets.

Exception: Where the 20-ampere circuit supplies a single bathroom, outlets for other equipment within the same bathroom shall be permitted to be supplied in accordance with 210.23(A)(1) and (A)(2).

This requires the circuit to be a 20A circuit, run using 12AWG wire throughout. It's not at all rare or unusual, by the way, to have a single bathroom powered entirely by a dedicated 20A branch circuit as you describe, so don't worry about any silly notions of providing "too much power" to the lights.

The only things you'll need to know is that the bath fan needs to draw no more than 10A in order to comply with the 50% rule in NEC 210.23(A)(2):

(2) Utilization Equipment Fastened in Place. The total rating of utilization equipment fastened in place, other than luminaires, shall not exceed 50 percent of the branch-circuit ampere rating where lighting units, cord-and-plug-connected utilization equipment not fastened in place, or both, are also supplied.

Unless you have one of those fancy heated bath fans, you shouldn't have any problem meeting this rule, as an ordinary bath fan only draws a few amps.

Note that you'll need an AFCI for your 20A breaker, and will probably want to bring power to a two gang box at the vanity for the GFCI receptacle and lightswitch, with separate 12/2 runs going from there to the lights/fan. If you only have a single gang box installed, and can't change it, you can still do this, but you'll be stuck with a GFCI/switch combo, which means your fan and lights will be on the same switch, stopping you from having a timer for the fan.

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    Just as a point of clarity for op, a receptacle is an outlet, an outlet is not necessarily a receptacle. From the NEC definitions, "Outlet. A point on the wiring system at which current is taken to supply utilization equipment." – NoSparksPlease Feb 17 at 0:01
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    Curious what the reason is for mandating 20A vs allowing 15A for a bathroom? In my house lots of receps in other rooms are 15A ckts. – UuDdLrLrSs Feb 17 at 14:58
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    Likely high-power devices like hair dryers. same as kitchens, where high-power kettles and toasters are used. – user60561 Feb 17 at 15:53
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    Not just the obvious hair dryer, but anywhere you have plumbing (restrooms and kitchens) you want a plumber to be able to run a motorized snake for cleaning DWV line, as well as provide adequate power to a wet vac for cleaning up messes. 15A isn't good enough for those scenarios, and the last thing you want to do in a wet area is force someone to use an extension cord. – Monty Harder Feb 17 at 16:35
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    @MontyHarder Those are edge cases - the reason is 100% because of hair dryers, which are almost universally 1800W appliances and consume an entire 15A circuit's capacity all by themselves. – J... Feb 17 at 18:13
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You are right on target with a 20 amp breaker and 12/2 with ground. You don't want 15 amps in bathrooms or kitchens due to heavy current draws from appliances and hair dryers. A 20 amp circuit in your bathroom should allow you to draw about 1900 watts safely (120v x 20 amps x 80%). Your lights and bathroom fan won't draw very much. Hair dryers vary but most don't draw more than 1500 watts or so - and that is only intermittently.

Importantly you want to make sure that all of your bathroom outlets are GFCI protected. This can be done at the breaker if it's a dedicated circuit or by installing a GFCI protected outlet in the bathroom. However, you probably will want to protect with a GFCI at the outlet. There is one advantage in protecting at the breaker - it will protect the entire circuit. The downside is if it trips the lights and fan will lose power as well as the outlets.

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    They probably want a GFCI outlet here, in order to keep the lights off the GFCI. (That way, accidentally tripping the GFCI won't leave them in the dark!) – ThreePhaseEel Feb 16 at 18:01
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    Good exploration of the hazards of putting the whole circuit on GFCI. – Harper - Reinstate Monica Feb 17 at 22:49
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14-2 requires a 15A breaker.

Code requires a 20A breaker on bathroom receptacles, so 14-2 is out of the question. 14-2 could be used for the hardwired loads, but then, you'd need a #12 20A circuit for the receps.

Bathroom receptacles have some special rules. They can only be on two kinds of circuits. One of the allowed types is your "dedicated to one bathroom" circuit: the same circuit can serve recep loads there, and also hardwired loads in that same bathroom.

However, if you trip that breaker, the lights will go out. That may be a problem from a usability point-of-view.

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