Electrical Circuit Question

[sroxberg]

I am considering running a 20 amp circuit for some light. I would prefer to run two 15 amp circuits but I'm out of room in the panel and have determined that I cannot add any 1/2 breakers to this panel.

So can I run a 20 amp circuit with 12 gage wire feeding the junction boxes and switch boxes. But I would like to run 14 gage shielded to each individual light from the junction box. The lights don't draw much if any power and the wiring inside the lights isn't 12 gage.

So is this allowed by code or just buy some new 12 gage shielded and run 12g everywhere?

[Bob10]

I have to ask why the desire to switch up the wire?  While I have 15 amp circuits in my house all the wire is 12 or larger.

[jlanciani]

Why shielded wire? Do you mean grounded? All permanently installed circuits must be grounded. 

And yes, you must run 12ga. or larger wire end to end if it is being protected by a 20 amp breaker.

[TDKPE]

The lights don't draw much if any power and the wiring inside the lights isn't 12 gage.

But they're listed (UL, CSA) utilization equipment, tested to be able to overload long enough to trip the breaker, including a 20A breaker, and including short-circuits and ground-faults (thousands of amps for perhaps half a cycle).

As already stated, 12 gauge end to end.  If you want to comply with the NEC.

[toolie]

The answer to OP question is no. Wire gauges lower than breaker rating are a no no.

[crokett™]

I'm confused that you say you can't add any more circuits but want to pull a 20 amp circuit? IF you are pulling a new circuit.why not just make it 15 A and then you can use the lower gauge wire? I prefer it to 12 Guage where appropriate because it's easier to pull and woek with.

[sroxberg]

I'm confused that you say you can't add any more circuits but want to pull a 20 amp circuit?  IF you are pulling a new circuit.why not just make it 15 A and then you can use the lower gauge wire?  I prefer it to 12 Guage where appropriate because it's easier to pull and woek with.

The issue is that I only have space for a single breaker.

I want to add some lights to the shop and plan to add 10 8 foot florescent fixtures that are HO. I'm assuming that is too much of a load for a 15 amp circuit, and I too would rather work and wire lights with 14g wire. So I was hoping for a hybrid.

I'll just run it at 20 amp and be good, I'm assuming that 20 amps will handle the lights.

[Snipe Hunter]

Pull out two breakers next to each other in the main panel. Buy a 4 pole 60 amp sub panel that accepts tendem breakers. You can pick this stuff at Home Depot. Set the sub panel right next to the main panel. Set a 2 pole 60 amp breaker in the main service panel to service the new panel. Move the two circuits you disabled to the new panel and you can install tandem breakers in the new panel to gain space.. I'm not a big fan of tandem breakers, they seem to fail more often that single pole breakers imho. Either way, you'll gain at least two new breaker slots.

[MikeBob]

The issue is that I only have space for a single breaker.

I want to add some lights to the shop and plan to add 10 8 foot florescent fixtures that are HO. I'm assuming that is too much of a load for a 15 amp circuit, and I too would rather work and wire lights with 14g wire. So I was hoping for a hybrid.

I'll just run it at 20 amp and be good, I'm assuming that 20 amps will handle the lights.

I am confused!! Code is 15amp 14ga wire, 20amp is 12ga wire.

[TDKPE]

I am confused!! Code is 15amp 14ga wire, 20amp is 12ga wire.

It is.  He was hoping to run 14 gauge copper to each fixture from a junction box fed with 12 gauge copper at 20A.  It appears the OP is now resigned to the need to use 12 gauge for all of it, as he should.

Or, as Snipe suggested, add a small subpanel right next to the main panel, moving one circuit to the new panel, so there's two slots available in the main panel for a 2-pole breaker to feed the new sub, thereby future-proofing the system. He could then run two or more 15A circuits with 14 gauge copper to the lights, as he originally wanted to do.