conductor over current protection limitations!

[casualty]

Have an issue about being able to use or not use 14 awg on a switch leg for luminares where the over current device is 20 amp. 240.4 (D) states that the largest over current protection for 14 awg copper is 15 amperes. The AHJ says it should be all 12 awg including the switch leg.

 

[infinity]

#12 is required for a 20 amp circuit based on the code section you quoted. Reductions in size are permitted elsewhere in the code such as in fixture wires or fixture taps but this wouldn't include a switch leg.

 

[h1h2h3]

I actually ran into this today. I found several lights in one of our buildings that had #18 fixture wire (ballast wire) run through FMC from the fixture to a junction box on the pearlings. I wasn't sure if this was allowed per the NEC and looked it up. According to 240.4 (D) and 240.5 (B)(2) it is. Nontheless, I didn't feel the tap was necessary and I wasn't a fan of the install, so I pulled it out and ran 12-2 to the fixtures instead.

If you look at table 310.15(B)(16) you'll notice asterisks that refer you back to 240.4 (D) (3+5). Here you'll find quite clearly that the NEC states that 14 copper is good for 15 amps and 12 copper is good for 20 amps, no more, except in a few instances like those Infinity mentioned.

 

[ActionDave]

I actually ran into this today. I found several lights in one of our buildings that had #18 fixture wire (ballast wire) run through FMC from the fixture to a junction box on the pearlings. I wasn't sure if this was allowed per the NEC and looked it up. According to 240.4 (D) and 240.5 (B)(2) it is. Nontheless, I didn't feel the tap was necessary and I wasn't a fan of the install, so I pulled it out and ran 12-2 to the fixtures instead. .....

Sounds like you replaced a fixture whip. Probably millions of them in service. They are safe.

 

[roger]

Sounds like you replaced a fixture whip. Probably millions of them in service. They are safe.

I agree assuming they are factory made whips.

Roger

 

[jumper]

I agree assuming they are factory made whips.

Roger

I remember there were discussions about this, but forgot the outcome.

Why cannot we make our own smaller gauge whips?

 

[roger]

Why cannot we make our own smaller gauge whips?

I think it's basically for the same reason we supposedly can't make our own light fixtures.

Roger

 

[don_resqcapt19]

There is no code restriction on making your own fixture whip.

 

[infinity]

There is no code restriction on making your own fixture whip.

We've been making them for as long as there have fixtures.

 

[templdl]

Have an issue about being able to use or not use 14 awg on a switch leg for luminares where the over current device is 20 amp. 240.4 (D) states that the largest over current protection for 14 awg copper is 15 amperes. The AHJ says it should be all 12 awg including the switch leg.

Is it part of a UL listed assembly?

 

[iwire]

We've been making them for as long as there have fixtures.

Yes, but I bet you are using full size conductors.

It is my understanding that to make reduced size fixture whips requires the use of fixture wire.

 

[infinity]

Yes, but I bet you are using full size conductors.

It is my understanding that to make reduced size fixture whips requires the use of fixture wire.

We either use full size THHN or reduced size say #16 or #18 TFFN fixture wire.

 

[roger]

Yes, but I bet you are using full size conductors.

That's what we do

It is my understanding that to make reduced size fixture whips requires the use of fixture wire.

Same here but for some reason we just never do it.


Roger

 

[iwire]

We either use full size THHN or reduced size say #16 or #18 TFFN fixture wire.

You guys seem to be the exception, as Roger mentions we know how but never bother.

But we usally daisy chain the power to fixtures anyway.

 

[infinity]

You guys seem to be the exception, as Roger mentions we know how but never bother.

But we usally daisy chain the power to fixtures anyway.

I wonder if you simply ordered #16 or #18 stranded wire what insulation it would have?

 

[iwire]

I wonder if you simply ordered #16 or #18 stranded wire what insulation it would have?

I think TFFN, I have tried to get THHN/THWN in 18 before with no luck.

 

[infinity]

I think TFFN, I have tried to get THHN/THWN in 18 before with no luck.

According to Table 310.104(A) for THHN and THWN #14 is the minimum size. I think that back in the old days when we ordered #16 "fixture wire" it was probably MTW.

 

[jim dungar]

I wonder if you simply ordered #16 or #18 stranded wire what insulation it would have?

I always ordered quad-rated TFFN/AWM/MTW/TFN
"Southwire Type TFFN or MTW or AWM may be used as fixture wire, ...."

 

[jumper]

I always ordered quad-rated TFFN/AWM/MTW/TFN
"Southwire Type TFFN or MTW or AWM may be used as fixture wire, ...."

IIRC, a lot of the wire I use has a TEW on it also. No clue why.

 

[GoldDigger]

IIRC, a lot of the wire I use has a TEW on it also. No clue why.

FWIW:

Southwire Type MTW/TEW or AWM is used for machine tool wiring and internal wiring of appliances. Typical applications
include wiring for refrigeration equipment, air-conditioning equipment, control wiring of machine tools, automatic washers, etc.
Type MTW rating permits use in (i) dry locations not to exceed 90?C (ampacity is limited to 75?C conductor temperature per
NFPA 79); or (ii) wet locations or other applicable locations when exposed to oil or coolant at temperatures not to exceed
60?C. Type TEW rating permits use in (i) dry locations not to exceed 105?C; or (ii) wet locations or other applicable locations
when exposed to oil or coolant at temperatures not to exceed 60?C. When used as AWM, intended uses are limited to dry
locations at temperatures not to exceed 105?C (applicable to both UL and CSA ratings). Standard product is marked Style
1015 and various other styles.

TEW appears to be another CSA classification.