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We have an RV sub panel at the rear of our house to connect our RV. The sub panel contains 50A/30A/20 Amp breakers. The breaker on the master panel feeding the sub panel is 60A.


The 20A breaker in the RV sub panel has 3 things connected: (1) a small gate operator via conduit, (2) a small underground sump pump connected to city waste water to dispense RV waste, (3) a single outlet in a nearby small 10’x12’ shed. The shed outlet is connected via conduit underground with 3 separate wires (THHN or similar). All were permitted and installed by a master electrician, inspected and approved.


Now wanting to install in the shed a 110V switched inside LED light (only 7 watts) and two outside shed LED lights (about the same), plus an additional outlet for a very small A/C heat pump which draws about 8A max.


Is there a code compliant way to install a small breaker for the light circuit to allow 14 gauge lighting circuit and switch, from the incoming 12 gauge wire, without upgrading the wire in the conduit or downgrading the 20A breaker in the RV panel?


Cannot see a sub panel available which would support 12 gauge lugs and a 15A breaker for a lighting circuit. My load requirements are minimal – just the small heat pump plugged in to the outlet and the shed lights.

Have considered using a blank face GFCI or AFCI for the lighting circuit but they seem to be 20A not 15 and not really suitable as a separate circuit.

Would like to rely on the 20A breaker in the RV sub panel to control everything but still reduce the lighting circuit with a single breaker if that is allowed.

Thanks
 

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I'd just wire it up with number #12 wire and forget it. The increased cost of panel and breaker (ground rods?) will be more the the differential cost of the wire.

Other than using smaller wire, the breaker inside the shed is not doing anything for you. Your weak link is all of the loads being fed off the 20amp breaker in the RV panel. If enough of them are on simultaneously, that's the breaker you will trip.

When you get ready to take the shed off that 20 amp breaker and put the shed on a panel other than the RV panel, that would be the time to discuss whether to use a subpanel or just a MWBC. If a 20 amp MWBC is the choice, you will still need the 20amp wire for those lights.
 

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Is there a code compliant way to install a small breaker for the light circuit to allow 14 gauge lighting circuit and switch, from the incoming 12 gauge wire, without upgrading the wire in the conduit or downgrading the 20A breaker in the RV panel?
Short answer: no. With a few exceptions that don't apply here, you can't have 14 awg wire on 20 A circuit.

Cannot see a sub panel available which would support 12 gauge lugs and a 15A breaker for a lighting circuit.
Are you sure of this? Are you saying that all 15 A breakers you see only support 14 gauge or smaller wires? That can't be true.
 

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Discussion Starter #4
Thank you.

By the NEC code, is it permissible to run 12 gauge to the lights and just rely on the single 20A breaker without down sizing through a 15A breaker?

Running a 20A circuit to a small outside light seems like overkill.
 

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Short answer: no. With a few exceptions that don't apply here, you can't have 14 awg wire on 20 A circuit.



Are you sure of this? Are you saying that all 15 A breakers you see only support 14 gauge or smaller wires? That can't be true.

I'm essentially looking to find a 20A sub panel fed with a single 12 gauge wire and appropriate sized lugs. Then install a 15A breaker on the sub panel to run a separate 14 gauge lighting circuit.

Do not want to upgrade the #12 wire. Not sure the code allows for that, or the alternative of running 12 gauge wire for the lighting circuit.
 

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I'd just wire it up with number #12 wire and forget it. The increased cost of panel and breaker (ground rods?) will be more the the differential cost of the wire.

Other than using smaller wire, the breaker inside the shed is not doing anything for you. Your weak link is all of the loads being fed off the 20amp breaker in the RV panel. If enough of them are on simultaneously, that's the breaker you will trip.

When you get ready to take the shed off that 20 amp breaker and put the shed on a panel other than the RV panel, that would be the time to discuss whether to use a subpanel or just a MWBC. If a 20 amp MWBC is the choice, you will still need the 20amp wire for those lights.
Thank you.

By the NEC code, is it permissible to run 12 gauge to the lights and just rely on the single 20A breaker without down sizing through a 15A breaker?

Running a 20A circuit to a small outside light seems like overkill.
 

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I see, sorry I misunderstood. Yes, 12 gauge wire is permitted for lighting circuit on a 20 A breaker. It may be overkill, but it sounds like the simplest solution.
 

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I see, sorry I misunderstood. Yes, 12 gauge wire is permitted for lighting circuit on a 20 A breaker. It may be overkill, but it sounds like the simplest solution.
Thanks for this. So, I could use a junction box with wire nuts, to individual feeds with #12 then - or just daisy chain everything?

I'm picking that I should look for a 20A light switch? Even though it is only passing mA?
 

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Yes you can put lights on 20 amp circuits.

The #12 isn't overkill, it is the appropriate sized wire based upon the breaker that is feeding it.

Yes you need a 20 amp switch.

It doesn't matter whether you have two 150w light bulbs or a 7 watt LED, 20 amp wire with a 20 amp breaker.
 
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