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Another weird NEC code question on Feeder Taps #220279 09/17/19 02:34 PM
Joined: Sep 2019
Posts: 19
pcsailor Offline OP
Member
Hello,

Another stumper of a question for me I could use some help with, even when I have the answer.

Here's the question:
"A "tap"transformer supply can use NM cable on the secondary side."
True or False

And the given answer:
"No 240.21(B)(3)(4)"

I just don't get this question at all.

Here's the code text from 240.21(B)(3)(4):
(4) The primary and secondary conductors are protected from physical damage by being enclosed in an approved raceway or by other approved means.

This would lead one to look at Article 334, NM cables, Yes?
Well, I have and don't see any relation to the question. 334.15(B) talks about Physical Damage Protection.

Before I even had the answer to this question I was stumped. I researched the following code threads without luck:
-Feeder Taps
-Transformers - in Article 250
-NM Cable, Art.334
-Separately Derived Systems
- Index lookup - Transformer ->Tap (nope) & Secondary Ties (no info), Taps -> Separately Derived Systems (No luck) & 250.30(A)(6)
-Internet searching -> no leads!!

What am I missing or is this question flawed?

Thanks,
Phil


Where ever you go, there you are.
2017 / 2014 NEC & Related Books and Study Guides
Re: Another weird NEC code question on Feeder Taps [Re: pcsailor] #220282 09/18/19 12:14 AM
Joined: Jul 2004
Posts: 9,411
G
gfretwell Offline
Member
It is not normal practice to put cables in pipe. I assume that is were they are going. "NM" implies simply using a cable and no raceway.
If perchance someone did stuff some NM in an EMT system I suppose it would be hard to fail but I would expect some funny looks.


Greg Fretwell
Re: Another weird NEC code question on Feeder Taps [Re: pcsailor] #220287 09/20/19 11:12 PM
Joined: Sep 2019
Posts: 19
pcsailor Offline OP
Member
Wow, that seems like a very oddball question.
Thanks for the explanation <:
Phil


Where ever you go, there you are.
Re: Another weird NEC code question on Feeder Taps [Re: pcsailor] #220288 09/21/19 09:49 AM
Joined: Jan 2018
Posts: 7
L
libellis Offline
New Member
Was this an isolated question or was it associated with a specific configuration and transformer tap conductor length? In particular, 240.21(B)(3) addresses taps supplying a transformer where the primary plus secondary length is not over 25 feet and clause (4) requires a raceway or other approved means. That's why NM cannot be used in that situation (unless in a raceway).

In fact, if you look at 240.21(B)(2 thru 4) each of the situations described has a clause requiring tap conductors to be in a raceway or other approved means. 240.21(B)(1) is slightly different, but still has a raceway requirement.

A suggestion - if you're only using the NEC manual for your studies, try to obtain a copy of the NEC Handbook. It contains the NEC manual and its purpose is to illustrate and help clarify NEC "gobbledygook" (at which it's only partially successful - you'll still have bald patches from scratching your head over NEC meanings.)

Re: Another weird NEC code question on Feeder Taps [Re: pcsailor] #220289 09/21/19 01:43 PM
Joined: Apr 2002
Posts: 7,121
HotLine1 Offline
Member
As said above, a current Handbook is worth it's weight in gold for sure!

Using the quoted code "And the given answer:"No 240.21(B)(3)(4)"

I guess the quoted Article (in a stretch) could be cited as there is no AWG for the NM given. The stretch is compliance with "ALL" ((1) thru (5) and (1) thru (9) line items within 240.21 (B) (3) and (4)

18 yrs of being an inspector, and 50 years in the trade, I have never come upon NM for a transformer secondary.


John
Re: Another weird NEC code question on Feeder Taps [Re: pcsailor] #220290 09/21/19 03:52 PM
Joined: Jan 2018
Posts: 7
L
libellis Offline
New Member
I'm thinking that maybe the purpose of the question was really about tapped conductors requiring raceway for this case (transformer) and NM was simply the cable used to make the point.

Re: Another weird NEC code question on Feeder Taps [Re: pcsailor] #220291 09/21/19 10:35 PM
Joined: Jul 2004
Posts: 9,411
G
gfretwell Offline
Member
I never saw NM in any commercial installation. It was always EMT and maybe some FMC or MC cable for whips.


Greg Fretwell
Re: Another weird NEC code question on Feeder Taps [Re: pcsailor] #220305 09/27/19 01:22 AM
Joined: Sep 2019
Posts: 19
pcsailor Offline OP
Member
Thanks All <:

Good News!!

I passed!!

Whew, tough test!

Thanks for all the support.
This forum helped alot <:
Phil


Where ever you go, there you are.
Re: Another weird NEC code question on Feeder Taps [Re: pcsailor] #220308 09/27/19 01:25 PM
Joined: Apr 2002
Posts: 7,121
HotLine1 Offline
Member
Congrats!!!

Don't be a stranger here at ECN....


John
Re: Another weird NEC code question on Feeder Taps [Re: pcsailor] #220312 09/28/19 12:26 PM
Joined: Oct 2000
Posts: 3,930
Bill Addiss Offline
Member
iagree

Ditto!!

cheers


Bill

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