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 rigid supports. Feet. | Size wire required. 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.”