Using 14AWG on 20Amp circuit

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  #1  
Old 01-15-16, 10:02 PM
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Using 14AWG on 20Amp circuit

I know that with 20Amp circuit one must use 12AWG wires...and that's what I have going from my main panel to the outlets, which are also rated for 20Amp....but then I am running additional 12AWG to the light switch and here is where I want to know if it would be safe to use 14AWG wires.
Before replacing the existing 14AWG, I stopped tonight thinking....do I really need to run new 12AWG wires from the light switch to the light fixture ???

I mean...the switch controls the light only and of course, no ceiling lamp draws near 15 Amp...never mind 20Amp....and so...do I really need to run new 12AWG wires for the rest of the circuit or can I just reconnect the switch with 12AWG coming into the box with 14AWG going out to the light from the switch?

The lights are end of the circuit....

thanks!
 
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Old 01-15-16, 10:26 PM
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Paul..... it doesn't matter what the device actually draws. The circuit is protected by a 20A circuit breaker requiring all wiring on that circuit to be able to handle 20amps.
 
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Old 01-16-16, 04:24 AM
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Why do you want to run 14ga wire instead of the correct 12ga?

To reinforce what PJmax said it's also a code requirement. You can not run lighter gauge wire regardless of the load. You may install a 15 amp breaker if it's not a kitchen or other circuit required to be 20 amps and convert it to a 15 amp circuit.
 
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Old 01-16-16, 05:14 AM
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thanks...I was sure this would have been wrong based on the code alone..... and I guess if it is against the code we can't say it is somehow "acceptable" or safe (don't want the house to burn down because of the wire getting hot)
the wire for the light is already there....so it would have saved me some time not to run a new wire, but always best to do it right and up to the code....

JUst to "explain" myself and my laziness of not wanting to run a new 12AWG in place of 14AWG:

I was more interested in the "physics" aspect of it.... the way I understand electricity, it's not like you have 5, 10 or even 100 AMp running through the wires at any given time... amperage is the measure of amount of electrical energy flowing through the device /appliance... it is the AMOUNT being used so to speak....so it depends on the sum of the devices plugged in into the circuit.
The breaker is there only to cut of the supply of electricity if and when the load goes above that breakers max. Amp load.....the breaker itself doesn't make the circuit "give out" 10, 15 or 20 Amp...

But again....you guys are absolutely right.... I shouldn't even think that just because I know not to draw more than 15 amp on that circuit, the next owner or family members would obey that stupid rule of mine.... Probably should have slapped myself for even suggesting that...
 
  #5  
Old 01-16-16, 09:57 AM
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Wire after switch is still considered branch circuit and if you use 14 AWG wire, it is violation of the code.
As long as the load on 14AWG wire will never go above 15A you will not have problem. However, this condition cannot be guaranteed as something could happen in light fixture or bulb that create condition where load is above 15A yet not a dead short.
If it was a dead short, 20A breaker will trip before damage to 14AWG wire is done, but this is not always the case.


If it is fairly easy to change remaining 14 AWG wire, replace with 12 AWG.
If not, you could change your breaker to 15A, unless you must have 20A on that circuit.
Also, it might be possible to pull wire from 15A circuit instead of 20A circuit depending on how your stud and joist is laid.
 
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Old 01-16-16, 10:44 AM
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I am running additional 12AWG to the light switch and here is where I want to know if it would be safe to use 14AWG wires.
Today it's a code violation, but it may not have been when the wiring was installed. Not so many years ago it was perfectly acceptable by code to use 14 gauge wiring for switchlegs, switch loops and for 3-way switch travelers all on 20 amp circuits. I am not sure when the code changed. I wouldn't worry about it any more than I would worry about a 16 gauge lamp cord plugged into a receptacle on a 20 amp circuit.
 
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Old 01-16-16, 06:42 PM
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I don't remember 14 gauge switch legs ever being approved in the last 30 years or so.
 
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Old 01-16-16, 07:19 PM
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The only way they may have been approved is if they fell under the six foot tap rule.
 
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Old 01-16-16, 09:23 PM
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The tap rules rarely applies, especially in residential.
 
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Old 01-17-16, 07:33 PM
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I don't remember 14 gauge switch legs ever being approved in the last 30 years or so.
30 years is not so many years ago! It had nothing to do with the tap rule. I don't know exactly when the code changed.
 
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Old 01-17-16, 08:37 PM
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I'm pretty sure that IF such a rule was once in existence it was more than forty years ago. I have code books going back to the early 1970s and I don't remember ever running across that rule.

And I agree with CasualJoe that it would not come under the tap rules.

Now it could easily be a LOCAL code rule, either in the not too distant past or even still on the books somewhere.
 
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Old 01-18-16, 07:46 AM
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I see 14 AWG switch / lighting loops on 20A / 12 AWG circuits pretty commonly in houses built in the 50s and 60s. I don't know if it was actually in the code book or just a common practice. Nonetheless, it's not allowed any more.
 
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