[SML] Twofers vs. codes

[stagecraft05 at designrelief.com]

On Sat, 23 Feb 2019, Mike Voytko <mv35 at nyu.edu> wrote:
> 
> Lighting folk: Anyone know what the deal is regarding twofers and electric
codes? 
> Need to replace a bunch of aging stock, and have heard that the molded
rubber-chicken 
> style is now the only type that meets code. Is this true?
> 
> Thanks very much,
> 
> --
> Mike Voytko
> Lighting & Sound Supervisor
> TSOA Theatrical Production
> New York University
> <mv35 at nyu.edu>
> 

Nothing about molded rubber chicken style in the Code, but that's probably
an easy way to get a listed product built. The Code does allow you to build
your own extension cords, but two-fers are not extensions.  Article 520 does
allow for Junior Service Cord in Two-fers (see the Code) which can make
assembly easier, but you do have to pay attention to temperature and
terminal ratings.  

You can always view the code online - www.nfpa.org/70.  Keep in mind that
your are ay be under a different edition of the Code or other local rules
may apply.  Remember that Article 520 modifies or amends requirements in
Chapters 1 - 4.  Some key excepts from the 2017 edition are here:

520.2 Definitions.
Adapter. A device used to adapt a circuit from one configura‐
tion of an attachment plug or receptacle to another configura‐
tion with the same current rating.

Breakout Assembly. An adapter used to connect a multipole
connector containing two or more branch circuits to multiple
individual branch-circuit connectors.

Two-Fer. An assembly containing one male plug and two
female cord connectors used to connect two loads to one
branch circuit.

(C) Overcurrent Protection. Overcurrent protection of
conductors for portables shall comply with 240.5.
520.69 Adapters. Adapters, two-fers, and other single- and
multiple-circuit outlet devices shall comply with 520.69(A), (B),
and (C).
(A) No Reduction in Current Rating. Each receptacle and its
corresponding cable shall have the same current and voltage
rating as the plug supplying it. It shall not be utilized in a stage
circuit with a greater current rating.
(B) Connectors. All connectors shall be wired in accordance
with 520.67.
(C) Conductor Type. Conductors for adapters and two-fers
shall be listed extra-hard usage or listed hard usage (junior
hard service) cord. Hard usage (junior hard service) cord shall
be restricted in overall length to 2.0 m (6.6 ft).

...
------------------------------------------------------------------
Mitch Hefter
NEC Panel 15, ETCP Certified Electrician
ETCP Recognized Trainer - Electrical
Co-Chair USITT Electrical Workshops