At the recent meeting of the Underwriters’ National Electric Association
it was decided that Cooper Hewitt lamps must have a cut-out for each
lamp or series, except when contained in a single frame and lighted
by a single operation, in which case not more than five lamps shall
be dependent on a single cut-out. The regulators must be enclosed
in non-combustible cases, and where subject to flyings of lint or
combustible material, all openings through the casings must be protected
by a fine wire gauze. Moore electric light tubes must be installed so
as to be free from liability to mechanical injury or of contact with
inflammable material. The high-potential coils and regulating apparatus
must be installed in an approved steel cabinet, which shall be ventilated
in such a manner as to prevent the escape of flame or sparks in case of
burn-out. The apparatus in this box must be mounted on slate, and the
enclosing case positively grounded. The supply conductors must comply
with the rules governing low-potential systems where such wires do not
carry current having a potential of over 300 volts.
Rule 8, section _d_, was amended to apply to auto-starters only, and
a new section was added to rule 60 governing the details of rheostat
construction. New rules regarding low-potential transformers follow: Oil
transformers must not be placed inside of any building except central
stations and sub-stations, unless by special permission of the inspection
department. Air-cooled transformers must not be placed inside of any
building excepting central stations and sub-stations, unless the highest
voltage of either primary or secondary does not exceed 550 volts, and
must be so mounted that the case shall be one foot from combustible
material or separated therefrom by non-combustible, non-absorptive,
insulating material, such as slate or marble. Where transformers are
placed at a lesser distance, a slab of slate or marble somewhat larger
than the transformer must be used, and where the transformer is mounted
on a side wall, the slate or marble must be secured independent of
the transformer supports, the transformer being supported by bolts
countersunk at least one-eighth inch below the surface of the back of the
slab and filled.
For wiring electric cranes the following rules were adopted: All wires
except bare collector wires, those between resistances and contact
plates of rheostats and those subjected to severe external heat, must
be approved, rubber-covered and not smaller in size than No. 12 B. & S.
Wires between resistances and contact plates of rheostats must conform
to No. 4-c, unless the wires are exposed to moisture, in which case
the insulation must also be rubber. Wires subjected to severe external
heat must have approved slow-burning insulation. All wires, excepting
collector wires and those run in metal conduit or armored cable, must be
supported by knobs or cleats which separate them at least one inch from
the surface wired over, but in dry places where space is limited and the
distance between wires as required by Rule 24-h cannot be obtained, each
wire must be separately encased in approved flexible tubing securely
fastened in place. Collector wires must be supported by approved
insulators so mounted that even with the extreme movement permitted the
wires will be separated at all times at least one and one-half inches
from the surface wired over. Collector wires must be held at the ends by
approved strain insulators.
Where the wires are arranged in a horizontal plane above the crane,
they must be supported at least every twenty feet if practicable, and
separated at least six inches, but if longer spans are necessary, the
distance between wires must be increased proportionately, the span in
no case to exceed forty feet. If not arranged in a horizontal plane,
they must be carried along the runways and must be rigidly and securely
attached to their insulating supports at least every twenty feet, and
if not arranged in a vertical plane, must be separated at least eight
inches.
Where bridge collector wires are over eighty feet long, insulating
supports on which the wires may loosely lie must be provided at least
every fifty feet. Bridge collector wires must be kept at least two and
one-half inches apart, but a greater spacing should be used whenever
it may be obtained. Collector wires must not be smaller in size than
specified in the following table for the various spans:
Distance between Size wire
rigid supports. required.
Feet. B. & S.
0 to 30 6
31 to 60 4
Over 60 2
Collectors must be so designed that sparking will be reduced to a minimum
between them and collector wires. The main collector wires must be
protected by a cut-out and the circuit controlled by a switch, cut-out
and switch to be so located as to be easy of access from the floor.
Cranes operated from cabs must have a cut-out and switch connected into
the leads from the main collector wires and so located in the cab as to
be readily accessible to the operator. Where there is more than one motor
on a single crane, each motor lead must be protected by a cut-out located
in the cab if there is one.
Controllers must be installed according to No. 4, except that if the
crane is located outdoors the wires between resistances and contact
plates of rheostats may be rubber-covered or bare or slow-burning if
properly supported. If the crane operates over readily combustible
material, the resistances must be placed in a fire-resisting enclosure;
or, if located in a cab, the cab must be constructed of non-combustible
material and sides provided which enclose the cab from its floor to a
height at least six inches above the top of the resistance.
The motor frames, the entire frame of the crane and the tracks must be
permanently and effectively grounded.
A number of recommendations were made calling for conductive coatings on
cables, outlet boxes and fittings in order to secure better electrical
contact at all points throughout systems in which they are used.
The following suggested changes in the rules were adopted: The fine print
note under rule 2, section a, was amended to read as follows: “Wires from
generator to switchboard may, however, be placed in conduit, provided
that proper precautions are taken to protect them against moisture and
mechanical injury. If lead-covered cable is used no further protection
against moisture will be required, etc.” Section c of the same rule
was amended by inserting the words, “where not in conduit,” after the
first word. The last sentence of the fine print note in rule 12, section
g, was amended to read: “The outer or weather end of conduit is to be
provided with approved devices having wires separated and bushed through
porcelain.”
A number of changes were made in rule 24. Section a, with fine-print
note, was stricken from the Code; section o was amended by making the
first recommendation “a turn of 90 deg., etc.”; section p was amended so
as to restrict the number of different circuits in the same conduit to
four two-wire or three three-wire; section x was changed by substituting
the word _or_ after the word _fastenings_ for _of_. Rule 24A was also
changed somewhat. Section d was amended so as not to prohibit the
installation of armored cable without the lead covering in buildings
of fireproof construction in locations free from moisture; the word
“underground” was omitted from the first line of the fine-print note
under section a. A new section was added as follows: “All bends must
be so made that the armor of the cable will not be injured. The radius
of the curve of the inner edge of any bend not to be less than one and
one-half inches.”
Rule 28, section e, was amended so as to exclude flexible cord from
show cases as well as show windows; the fine-print note under section g
was omitted. A number of minor changes were made in the rules governing
the wiring of theaters, principally in inserting the words, “or armored
cable,” so as to permit the use of the latter as an alternative to rigid
conduit. The other changes have to do with the details of construction,
fitting, etc. Among the miscellaneous suggestions adopted were the
following: All self-fastening knobs, cleats and supports must be secured
by suitable screws; wires in molding must be in continuous lengths from
outlet to outlet or from fitting to fitting; sockets or rosettes cannot
be used to dead-end a circuit; soap-stone can be used as an alternative
for slate or marble; and ends of flexible wire need not be soldered
before insertion under binding posts, as called for in rule 14, section c.