House built in the 1940s. When remodeling a bathroom, I put a 20A circuit in the panel and ran new 12/2 wire up to the bath to GFCI outlets. I continued the circuit up into the attic to power an attic bathroom exhaust fan.

In the attic there is a rickety old pull-chain light fixture attached to the original 1940s wiring, which has two conductors but no ground. A prior owner of the house attached 14/2 wiring to this old 1940s wiring, and had simply tied the ground wire of the 14/2 to the junction box.

I would like to detach the 14/2 from the ungrounded old wiring and attach it to the new 20A 12/2 wire in the attic.

All the receptacles on the 14/2 are 15A.

Does mating 14/2 to 12/2 present any safety hazards if nobody tries to draw more than 15A on the "extended" 14ga leg of the circuit?

3 Answers 3


Nope. Any circuit with any 14 AWG wire in it, is a 15A circuit. it requires a 15A breaker and cannot have 20A receptacles.

You cannot put a non-bathroom load on a bathroom circuit. Whatever circuit now powers this attic light, leave it that way unless you want to pull another circuit. And if you do, go ahead and pull 12 AWG. You can always use larger wire than required. It will still be a 15A circuit as long as it still has any 14 AWG.

Share the ground!

You are welcome to use the ground in the bathroom circuit to provide ground to the ungrounded attic light circuit, provided both are supplied out of the same breaker panel. This is a ground retrofit, and the rules (NEC 2014) now give you wide latitude to do this. Your 12 AWG ground wire is enough to ground any 15A or 20A circuits (plural) served by the same panel. Doing so should not affect your GFCI, even if the old circuit has a problem.

The circuits need to come out of the same panel, so if the circuit breaker for one is in a main panel, and the other breaker is in a sub-panel, then no.

Bathroom circuits

Code originally required a dedicated circuit for bathroom receptacles. It could serve as many bathrooms as you wanted, provided it served only receptacles. Obviously this necessitated a second circuit for lighting and fan. This could be taken off a circuit for another room.

Later, Code was revised to allow a different arrangement: the dedicated receptacle circuit could also serve other bathroom loads, if it served only one bathroom. Other loads might include lighting, fan, etc.

Bathroom loads are ones that exist to serve the bathroom and are used whilst in the bathroom. A bathroom fan is, but an attic light is not.

50% limit on fixed loads

This comes up anytime you have a fixed, installed, built-in load that takes a lot of power. In bathrooms this could be a heat lamp or air heater, or point-of-use water heater. If are circuit has fixed (built-in) loads which total more than 50% of circuit capacity, in other words 1200W on a 2400W circuit, *then you can't have any receptacles on that circuit

You can piggyback other fixed loads on that dedicated circuit, as long as you remain under 80% of circuit capacity (1440W for 15A, 1920W for 20A).

  • Remember, this is a circuit to bathroom receptacles. Jan 27, 2017 at 21:06
  • May I ask a followup? How is non-bathroom load defined? Are the lights in the bathroom ceiling considered part of the bathroom load? How about the exhaust fan? They are both controlled by switches on the bathroom wall reachable when standing at the sink, so I protected the light and fan switches using the bathroom GFCI outlets.
    – mr blint
    Jan 29, 2017 at 11:36
  • m.ecmweb.com/cee-news-archive/bathroom-circuit-receptacles Yes the bathroom fixed loads are fine. Jan 29, 2017 at 15:50
  • Thanks for that. As I understand it, since I have bathroom lights and bathroom exhaust fan on the circuit to bathroom #1, I must run a separate circuit to bathroom #2.
    – mr blint
    Jan 29, 2017 at 16:50
  • that is correct. Jan 29, 2017 at 18:08

You cannot do what you propose. You are good by running a 20A circuit for a bathroom receptacle circuit, it is required. By adding #14 to the circuit would mandate that you downgrade the breaker to 15A which would not be code compliant.

Your best bet is to run a new #14 circuit to re-feed this non-grounding circuit.

  • If I don't run new 14 from basement to attic, my choice would be to replace the 14/2 with 12/2 and upgrade the outlets that were at the end of the (now replaced) 14/2 with 20A outlets?
    – mr blint
    Jan 27, 2017 at 20:43
  • 2
    Well, by extending this circuit outside the bathroom you create another violation. Bathroom receptacle circuit cannot serve loads outside the bathroom. Depending on the loads this may be a trivial issue. ...... No, you do not need 20A receptacles on a 20A circuit, as long as there is more than one receptacle or at least one duplex. This is an NEC thing, Canada is different. Jan 27, 2017 at 20:45
  • Does every bathroom need its own homerun circuit? I was going to extend the circuit from one bathroom to another.
    – mr blint
    Jan 27, 2017 at 21:00
  • Can a ground wire go between junction boxes? It's mainly the lack of ground that is making me want to do something with the 14/2, detach it from the old wire.
    – mr blint
    Jan 27, 2017 at 21:02

If all you are doing is changing the wire to a larger gauge, you are fine. By changing the breaker to 20A from 15A, without changing the outlets, you would be in code violation. I would wonder what on Earth you are running in the bathroom that requires more than 15 amps! NEC code for a bathroom in a residence is 15A. I would recommend using a 15A breaker to avoid liability should anything fail and end up being the cause of the house fire. Insurance doesn't pay for out of code installation.

  • So a 15A circuit can use 12/2 and we'd be good if I changed the breaker to 15A?
    – mr blint
    Jan 27, 2017 at 20:20
  • 14/2 has a max amp rating of 15 amps, so that wouldn't be a proper installation. Jan 27, 2017 at 20:27
  • But I said that I would change the breaker to 15A.
    – mr blint
    Jan 27, 2017 at 20:27
  • Right change the breaker to 15A and you are good. Jan 27, 2017 at 20:29
  • 1
    @MichaelMarkham, a receptacle circuit to a bathroom under the NEC must be 20A. You cannot simply replace it with a 15A and remain compliant. Also, the receptacle rating does not need to be 20A on a 20A circuit, provided there is at least one duplex (more than one receptacle). Jan 27, 2017 at 20:38

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