Reducing wire size in residential

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bkelly

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Can anyone help with a code reference on reducing wire size in residential. I allways thought that you could not reduce wire size, say in homeruns run in #12NM and then reducing to #14 for the rest of the circuit. Great resource, thanks for everyone input.
 
You can reduce branch circuit wire sizes anywhere in the run as long as the OCPD is not greater than the smallest conductors ampacity.

IOW's, if you ran #12 a certain distance for VD and then reduced to #14 it would be fine, but you would be limited to a 15 amp OCPD. (this is barring motor and A/C exceptions)

Roger
 
bkelly said:
Am I losing it or was it once in the code?
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Some people have mistaken 210.19(A)(4) as allowing this but it is not the case.

It is true that in the past some areas overlooked people reducing all switchlegs and taps to receptacles, but this is / was not allowed per the NEC.

Roger
 
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bkelly said:
Am I losing it or was it once in the code?
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You may well not be, depending upon your work history and the jurisdictions you've worked in.

I did a custom bath rewire in an early '60s rambler in a staid and well-to-do neighborhood. The original wiring was heavy steel flexible conduit, throughout the dwelling. At the panel there was still framed behind glass, an 8" x 10" certificate of compliance stating how well the dwelling was wired. The primary feature of the wiring that had any "better" features than the NEC minimum was that all the homeruns were a gage larger than they were fused at.

There were a lot of homes in this area, all wired to this "higher standard". I can imagine, with the limited communications of that day, that more than one installer, working day after year in this neighborhood, would come to believe that such oversizing is "required" by Code.

And I can imagine apprentices inferring that one could drop a gage size out on the end of a branch circuit.

Classic origins of urban myths.
 
bkelly said:
I allways thought that you could not reduce wire size, say in homeruns run in #12NM and then reducing to #14 for the rest of the circuit.
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BK, think of it as increasing the HR, and not decreasing the circuit wiring. Why would the NEC prohibit using larger than the minimum wire size? As long as the EGC is upsized, it's perfectly compliant.

Now, think about possible ramifications. What if, say, someone taps into the #12 somewhere, expecting it to be a 20a circuit, the load trips the 15a, and they see #12 and install a 20a breaker?

My suggestion would be to cut the #12's, black, white, and red (if used), about 6" or so inside the panel, and continue to the breaker(s) and bus with #14. Anyone seeing this done should get it.


Added: I know Bob is going to give me grief for this :)smile:), but:

If several homeruns are really all that long, a sub-panel should be considered. Load diversification should minimizine the feeder requirements, and labor and materials can actually be reduced.
 
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