14/2 on a possibly 12/2 circuit


Old 11-05-06, 09:25 AM
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Question 14/2 on a possibly 12/2 circuit

Need some advice. I have an older home, 1960's in Tennessee.
The wiring is not marked for size.
I am adding a 15 amp outlet and the closest circuit for me to splice into is a lighting circuit. This circuit is on a 20 amp breaker but I cannot tell what gauge the wire is.
Am I in trouble if I spliced in with 14/2 guage wire and it is actually 12/2?
How can I tell - is the 20 amp breaker a good indication that it's 12/2 circuit?
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Old 11-05-06, 09:31 AM
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If it indeed is a 20A circuit, you will be in trouble extending it with #14 wire. Also, if it is ungrounded, you cannot extend that at all.
Old 11-05-06, 09:59 AM
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As classicsat has stated, you cannot do this.

20 amp circuits require 12 gage wire (minimum).

Also heed his comment about the circuit being grounded. If the circuit is not grounded, you cannot extend it. Finally, aluminum wire was used quite a bit in the 60s. If this circuit is aluminum wire, do not extend it at all, regardless of any other factors.
Old 11-05-06, 10:44 AM
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Keeping classicsat and racraft’s cautions in mind, one way to test a wire’s gauge is to take your wire strippers and, while holding them closed, try to insert the wire into the 12 and 14 gauge stripping holes (push gently so as not to damage the wire).

The strippers are designed to cut through the insulation without damaging the conductor, so if the wire is 12 gauge, it will be able to pass through the 12 gauge hole but not through the 14 gauge. If it is 14 gauge, it will pass through both, but will be more snug in the 14 gauge and have wiggle room in the 12 gauge.
Old 11-05-06, 10:53 AM
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Smile Thanks

I changed it to 12/2 - thanks for the quick replies - much appreciated.

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