14g Protection On 20a Breaker? - Electrical - DIY Chatroom Home Improvement Forum

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Old 04-27-2011, 11:54 AM   #1
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14g protection on 20a breaker?

OK, so long story short, I ran a 12-2 from an (as yet) unused 20a breaker in my panel to a new shed. (Through the attic and then down the side of the house in sch40pvc to a nice little metal box mounted on the exterior of the house that came preinstalled with a 20a gfci outlet and a 20a switch) I want to run 12g to 20a outlets for my tools and stuff. But... on advice from a neighbor who is a GC I wired overhead lights with 14 g including 14-3 to two 3way switches. While I know the lights won't draw much amperage, in the case of a short or partial short, the 14g wire won't be protected by the 20a breaker in the panel, right? It also won't really be protected by the gfci, right? So... rather than rewiring the lighting... (finally the question)...

Can I install a 15a breaker/fuse at the junction between the 12g and the 14g to the lights?

A fuse would be fine with me because this is very unlikely to ever short/blow. The lights are flourescent so no one will come along one day and screw a little outlet adapter in the plug.

I think my approach is safe and sound, but maybe still not legal/code. Thoughts?


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Old 04-27-2011, 01:07 PM   #2
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Once you added the 14 ga. wire to the circuit it now means you need to reduce the breaker to a 15 amp.

GFI's do nothing to protect from overload.


Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
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Old 04-27-2011, 01:11 PM   #3
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the problem with putting smaller gauge wire on a over current protection device than rated for is that the wire will heat up to unacceptable temps before the OCPD would get upset.

So lets say I put 14ga wire on a 20a breaker(we know 14ga is only good for 15a by code) It is possible and all together to likely that the wire would heat up to burn nearby objects before the breaker would trip.

If there is installed 14ga wire in a given location you have two choices, one install a 15a breaker or to replace the wire with 12ga wire.

It is not practical to install a OPCD at a remote location. I recommend that you down size the breaker to 15a
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Please follow the code - its there for your safety no matter how inconvenient.
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Old 04-27-2011, 02:06 PM   #4
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YOu can't just install a breaker in a junction box. You would need to install a proper sub panel.
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Old 04-27-2011, 02:45 PM   #5
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Thanks Cowboy, I get the concept. I disagree that it is 'likely' however, given the current draw of two flourescent light fixtures. The fixtures themselves have wimpy wire connectors (much smaller than the 14g).
Is it OK to make a subpanel off of a 20a 12g run to the main panel? What if I wire the lights and switches to a lamp cord and "plug it in" to a 20a recepticle?

Looks like I'm rewiring the lights. uggh.
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Old 04-27-2011, 02:49 PM   #6
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The easiest solution to this problem is to install a fusible disconnect (the kind used for air conditioners, hot tubs, etc.) where the #14 wire connects to the rest of the circuit. Install a 15A (or less) fuse in the disconnect. Only one half of the disconnect would be used, since there's only one hot conductor. This is a very strange solution and not a normal way to wire things - but it is safe, and as far as I can tell, code compliant. Fusible disconnects only cost about $15.
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Old 04-27-2011, 02:56 PM   #7
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I like it... thanks.


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