Theatre Design & Technology - Summer 1992 - 50

releyision were concerned, and rhe
realizarion rhar major changes were raking
place in our rechnology was nor evidenr
ro rhe jurisdierional aurhoriries. The firsr
crisis came in abour 1968 ar rhe Orange
Bowl Parade in i\!iami, FL. This is a
nighrrime parade wirh illuminared floars
held on December 31 each year prior ro
rhe Orange Bowl foorball game rhe nexr
evenll1g.
On rhe fronr page of rhe New Year's
edirion of one of rhe i\!iami newspapers
was a phorograph. The phorograph
showed a small child sining on a marion
picrure-srde spider box (splice box) of
rhar era, earing an ice cream cone. The
spider box was an oak box wirh rhree
venical pieces of copper busbar ro which
4/0 feeder cables were clamped.
10rmally, rhere are rubber flaps on rhe
sides of rhe box rhar when down cover rhe
exposed busbars. In rhis case rhe rubber
flaps were nor down. The child's legs were
wirhin inches of rhe busbars; rouching
rhem could have elecrrocured rhe child.
To compound rhe marrer, rhe welding
cable was in rhe gurrer and rhere was
warer in rhar guner!
When rhe relevision lighring direcrors,
engineers, and elecrricians saw whar
mighr have happened, rhev began ro
invesrigare rhe use of welding cable and
spider boxes. Following rhe invesrigarion,
rhe indusrry adopred irs own recommended pracrice ro use only UL lisred
600 voir welding cable. Concurrenrly, rhe
morion picrure indusrry in Hollvwood
ourlawed rhe wooden spider box and
borh i\!ole-Richardson and \Vesringhouse
Elecrric developed new UL lisred spider
box sysrems.
Ir was rhoughr rhar all was righr wirh
rhe world. In rhe early '70s rhe Natio/lal
ElectriCf11 Code added a clause ro Anicle
520 -53 (h) specifying rhar onl\" Tvpes ,
SO, ST, and STO cables were permirred
as "supply conducrors." This presenred a
unforseen problem. All of rhe 5 rype
cables are, by UL requiremenrs, rwo or
more conducrors. There was no such
producr as a single conducror Tvpe SO
cable. Our indusrry was unable ro comph'
wirh rhe brer of rhe code. \X/hile single
conducror Type \V and rwo conducror
Type G cables were manufacrured, rhev
had been developed for rhe mining
indusrrv. and mer rhe I\line Safefl'. and
Healrh Adminisrrarion (i\lSHA)
srandards. i\ Ianufacrurers of rhe Tvpe \'\1
and G cables were unaware of a m,uker
ourside of rhe mining indu rry, and wcre
unwilling ro spend rhc monel' in
submining rhe produer ro UL for rcsring.
During rhe 1980 iYtltio/lal Electrical
Code proposal cycle, rhe
SITTs
48

1992 SUMMER

TD&T

l\arional Elecrrical Code Commirree
wrore a proposal ro include Type Wand
G cables, bur rhis was rejecred by rhe
Code i\ laking Panel. Nor unril rhe 1984
Olympics did rhe siruarion become so
obl'ious rhar somerhing had ro be done.
j\\osr of rhe 1984 Olvmpic venues
were wired wirh 4/0 welding cable. In
some siruarions ir was used for 480 voir
disrriburion (remember, rhe label said 600
volrs). An elecrrical inspecror rook a
crirical look ar welding cable and found
rhar all of our assumprions were wrong.

WHAT'S WRONG
To undersrand whar is wrong wirh uSll1g
welding cable, you musr firsr be familiar
wirh rwo publicarions. The firsr is rhe
Natio/lal Electric Code published by rhe
Narional Fire Prorecrion Associarion
(NFPA), Barrervmarch Park, Quincy,
i\\A. The second is rhe Electrical
CO/lstructio/l }\/aterials DirectOl)' (Green
Book), published by Underwrirers
Laborarories, Inc., 333 Pfingsren Road,
! orrhbrook, IL 60062.
The Electrical COll5rructio/l }\/arerials
Direcrol)' is a lisr of all elecrrical
consrruerion producrs which ha\'e been
found ro compl~' wirh appropriare safery
requiremenrs by UL. Ir is imporranr ro
undersrand some of UL's rerminology.
Firsr of all, norhing is "UL approved." UL
will only list, classify, or recog/lize a
produce The difference berween rhese
rhree caregories is rhar a recognized
componenr is a device rhar wirh orher
devices are assembled rogerher ro form an
end produce A recognized box conraining
a recognized rransformer and a recognized
rerminal srrip would consrirure such an
end produce
The manufacrurer of rhis end produer
can in rurn submir rhis box wirh rhe
rransformer and rerminal srrip ro UL for
invesrigarion and resring for ir ro become
a listed or classified produce The facr rhar
all of rhe componenr pans are already
recognized bv L means rhar rhe produer
evaluarion may be less cosrly ro rhe
manufacrure as some pans have been
prel'iouslv resred. sing recognized
componenrs also expedires rhe resring
process. The manufaerurer's producr will
be resred bv L ro rhe appropriare safery
requlremenr, or L may deer ro develop
a new resring procedure if rhe produer is
nor covered b~' an exisring srandard. Once
UL has lisred rhe producr, rhe
manufacrure is obligared ro conrinue ro
produce rhe same produce Any variarion,
such as rhe change in componenr manufaerurers from one model ro anorher, may
require a resubmission ro UL for a revised

lisring.
"Lisred" can cover a single irem or an
assembly of componenrs which has been
submirred ro UL, resred, and lisred for
use under rhe provisions of rhe resring
srandard. Classificarion covers rhe
propenies of rhe producr, limired hazards
ro life or propeny, suirabiliry of rhe
producr ro a specific use, and such orher
condirions as L may derermine.
Welding cable is a listed produce Ir is
In a separare UL caregory known as
"(Zi\\AY)." Currenrly rhere are seven
manufacrurers of UL lisred welding cable.
However, rhe imponanr informarion for
our indusrry is rhe paragraph defining rhe
use of rhis cable under rhe resring
procedures devised by UL. Ir srares:
Welding cable is a single-conducror cable inrended for use in
accordance wirh rhe Natio/lal
ElectriCf11 Code, Arricle 630, Parr E
in rhe secondary circuir of elecrric
welders. Ir is rared 60, 75 or 90°C
and 100 or 600 volrs. The volrage
and remperarure rarings may be
idenrified by rag marking and by
prinring on rhe surface of rhe
insularion. Cables are rared 60°C,
100 volrs maximum unless
marked orherwise. The conducrors are flexible srranded copper,
No.8 AWG - 250 MCM, rhe
individual srands of which are o.
34 - 30 AWG.
Kev words in rhe above sraremenr are
"inrended for use" and "secondary circuir
of elecrric welders." No where in rhis
sraremenr are rhe words "feeder cable" or
"power disrriburion." Furrher informarion
is found in rhe Natio/lal Electrical Code as
referenced above. Anicle 630 Parr E IS
rirled "Welding Cable" and srares:
630-41. Conducrors. Insularion
of conducrors inrended for use in
rhe secondary circuir of elecrric
welders shall be flame rerardane
Once again, rhe reference is quire specific
rhar welding cable is for use on rhe
secondary circuir of an elecrric welder.
Furrher, UL Srandard 551 covering
rransformer rype welding machines limirs
rhe secondary open-circuir volrage ro 100
volrs maximum, nor 120 volrs. The 600
voir raring on welding cable permirs ir ro
be in enclosures, cable rrays and racell'a~'S,
,1Ild inrermixed wirh power cables ha\'ing
volrages of 120 ro 408 volrs so as ro
comply wirh Secrion 300-3 of rhe NEe.
And ir is here rhar rhe problem lies.
Once vou usc rhis producr for power
Table of Contents for the Digital Edition of Theatre Design & Technology - Summer 1992
