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# 14-gauge Wire on a 20-Amp Circuit...Oh Boy

#1
03-07-17, 09:38 PM
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14-gauge Wire on a 20-Amp Circuit...Oh Boy

So I have read "all over the place" that one is not to use 14-gauge wire on a circuit that has a 20-amp breaker. However, I have not read an explanation as to WHY that is so. I.e., what is the REAL risk/danger? It is not that I want to do it, but there is a legitimate reason I ask, and I will provide the rationale for my asking afterwards (assuming I get feedback). Thanks much in advance!

#2
03-07-17, 09:50 PM
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The wire is not heavy enough to handle the heat of the load that could be imposed on it so a #14 is limited to 15 amps to provide a safety measure.

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03-08-17, 03:20 AM
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Another answer would be that the 20 amp breaker most likely won't trip on overload of the 14 gauge wiring, making the wiring a fuse, that will burn before the breaker trips causing a possible fire.

#4
03-08-17, 07:14 AM
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Thank you both. How REAL is the risk of actual fire or other hazard? I mean is it a legitimate risk or one that for all intents and purposes is only theoretical ("on paper only"). What I mean by that is kind of like an automobile's speed potential. Most cars, according to the speedometer, can reach 120-140 mph, which of course presents a huge danger to themselves and others. However, even the absolute most aggressive (crazy?) drivers don't or can't push 90 mph or so. (While someone going 50 mph on a highway can also be a danger under the "right" circumstances...a point I make to suggest that even properly wired circuits are not absolutely immune to accidents).

Not trying to be difficult here...just trying to get a sense of the REAL risk in normal daily household operations.

Another thought that crosses my mind...say you have a by-the-book 20-amp circuit, wired with 12-gauge cable. Now, at the end of the line, you add a simple light fixture. Nothing else. Most light fixtures have stranded THIN wire. (I imagine it is not even the equivalent of 14). To PCBOSS's post, wouldn't the heat generated be too much for the last few inches of run to the light bulb?

Things i think about...

#5
03-08-17, 07:21 AM
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The insulation on fixture wires is different than the wiring in the walls and has a higher temperature rating. Also the fixture load is known and the wires are sized for that load.

#6
03-08-17, 08:09 AM
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What keeps me awake at night is knowing that all the 20A circuits in my house terminate on cheap contractor grade 15A receptacles with lousy stab-in connections. Not a single 20A receptacle anywhere.

OK not really...I sleep fine.

#7
03-08-17, 10:08 AM
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Most 15A receptacles are rated for 20A pass thru.

Since you know you have back stab connections..... fix them now. Why wait for problems.
At one time you could use #12 wire in the back stabs. Now they are sized for #14 maximum wire size.

This picture was posted here by a member who got to witness first hand how effective the back stab connections really are.

#8
03-08-17, 12:19 PM
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OK, so the reason I asked the question originally was...

I was mapping out all the circuits in my house, built in 1987. Over the years, a second panel was added by an electrician, as I did major renovations, including a full kitchen addition, and finishing the basement. But the breaker panel labeling never kept up, and I have had no idea what to turn off whenever I did my own electrical work, etc. I just flipped by trial and error.

Long story short, I went to add lights to an attic above the attached garage (extra storage space). Until now, I used an extension cord with work light, and was tired of tripping over it. So, after wiring everything, I went to tap into a circuit that was powering a couple simple lights in the garage, only to realize that it was 12-gauge with a 20-amp circuit, while i had done my new work with 14-gauge. Darn! So this provided the impetus to FINALLY get around to mapping out the circuits.

What did I find? Besides strange pairings (like random receptacles on opposite sides of the large house on the same circuit), most of my breakers are 20-amp, with slots having been mostly doubled-up. Yet, a bunch of the circuits are wired with 14-gauge wire!!! (I know cause I have since done my own renovations). Most of the "professional" re-work impacting the panel was done in 2003-04. Yet here I am, +13 years later, with 6 of us in the house, all of us plugged in to the max, so to speak...and yet...(thank goodness)...no electrical issues...???

#9
03-08-17, 01:21 PM
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Many circuits do not run anywhere close to the maximum. This would keep the heat down and lower the risk of fire. It still does not make it correct.

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