4

My refrigerator line is 20 amp with 12 gauge wire. Can I tap into that with 14/2 wire, and run a light switch and 1 LED light?

  • Well should I run 12/2 wire then? I figured since it was such a small amount of current I could run 14 – Nate Feb 14 '18 at 0:19
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    If you properly splice 12/2 into the existing circuit, then you can use that to supply a light. Make sure you do all work in an accessible junction box, etc. Unless you're running 50+ feet, 12/2 isn't all that much more than 14/2 anyway. – Hari Ganti Feb 14 '18 at 1:24
  • Is the refrigerator the only thing in the circuit now? – Kris Feb 14 '18 at 2:06
  • Yes, the refrigerator has it's own line. I'm running one led can light for my pantry and that's all it's for. It will all be done in the junction box that exists now. – Nate Feb 14 '18 at 3:01
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    The only place I have ever seen tap rules used on branch circuits in a home is on the range circuit in conduit. – Ed Beal Feb 14 '18 at 14:35
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You must use 12/2 to extend a 20amp circuit. -Or- the breaker can be downgraded to 15amp if the circuit contains 14. (If downgrading the circuit, you should also tag the wire in the panel "circuit contains 14 gauge wire" to eliminate confusion in the future.)

What you're missing:. Under normal circumstances that segment of the circuit would normally carry little watts/amps as you point out. However in the event of a fixture fault, or even defective bulb in that fixture causing a direct short, the wire would overheat and catch fire, because it's 15 amp wire carrying a dead short.

  • In an industrial context, there's a section of code called the Tap Rules which cover "too-small" wire branched off a trunk. However there are a bunch of other protections in that code - not least, mandatory steel conduit/raceway - to avert disaster. – Harper Feb 14 '18 at 2:26
4

NO. The whole circuit needs to support the 20 amps (12 gauge).

My answer is based on common sense. I am no electrician, just a handy guy.

  • Your common sense has correctly captured the concept that breakers protect wires and devices. Indeed, given a partial short, the 14AWG wire would overheat faster than the breaker expects, so the (delayed) thermal-trip protections in the breaker would trip too late. – Harper Feb 14 '18 at 2:25
  • So from the plug run a 12/2 wire to a 15 amp tripper outlet then can i run 14/2 wire to the switch then to the light? – Nate Feb 14 '18 at 3:09
  • @nate there's no such thing as a 15A tripper outlet. Some people think GFCIs are also overcurrent devices but they're not, they wouldn't know or care if you passed 30A through. In fact 15A GFCIs are rated for 20A passthrough. You cannot buy a GFCI+receptacle that is only 15A. – Harper Feb 14 '18 at 22:48
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You could put an inline fuse that's < 16A in the junction box to protect the 14 AWG wire from overload. 14AWG is not meant to carry more than around 15 Amps unless it's in the open air to allow cooling.

edit: It's only for safety. In case someone still wants to do it improperly and use 14 AWG wire on a 20A circuit. Of course it's not the proper way to do it, but it could be the only way to save a ton of money without compromising safety if the 14 AWG wire is already installed.

  • Fuses are an outdated means of protecting mains circuits. – sleblanc Feb 15 '18 at 2:51
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    The problem here is the "inline" part of "inline fuse". You can get a type S fuseholder in a plate that mounts to a 4" square box, but even then...I'm not sure if that'd be Code compliant (feeder/branch hybridization problems + issues with a branch circuit OCPD outside a switchboard or panelboard) – ThreePhaseEel Feb 15 '18 at 4:33

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