« НазадПродовжити »
saddles of greater width than the metal of the staple, hy which possibility of injury to the tube may be prevented.
6. In damp places, attached to glass or porcelain insulators, and separated ten inches or more.
7. When passing through walls, floors, timbers, or partitions, treated as in central stations under like conditions.
Lamps and Other Devices.
Arc Lamps—Must be in every case:
1. Carefully isolated from inflammable material.
2. Provided at all times with a glass globe surrounding the arc, securely fastened upon a closed base. No broken or cracKed globes may be used.
3. Provided with a hand switch, also an automatic switch, that will shunt the current around the carbons should they fail to feed properly.
4. Provided with reliable stops to prevent carbons from falling out in case the clamps become loose.
5. Carefully insulated from the circuit in all their exposed parts.
6. Where inflammable material is near or under the lamps, provided with a wire netting around the globe and a spark arrester above, to prevent escape of sparks, melted copper or carbon.
Incandescent lamps in series circuits, having a maximum potential of 350 volts or over, must be governed by the same rules as for arc lights, and each series lamp provided with a hand switch and automatic cut-out switch; when lights are in multiple series, such switches and cut-outs must not control less than a single group of lights. Electro-magnetic devices for switches are not approved.
Under no circumstances will incandescent lamps on series circuits be allowed to be attached to gas fixtures.
CLASS C.—INCANDESCENT (LOW PRESSURE) SYSTEMS.—300 VOLTS OR LESS.
Outside Overhead Conductors—Must be:
1. Erected in accordance with general rules for arc (series) circuit conductors.
2. Separated not less than six inches, where they enter buildings as service conductors, and be provided with a double pole fusible cut-out, as near as possible to the point of entrance to the building, and outside the walls when practicable.
Underground Conductors—Must be:
1. Provided with suitable protecting devices at the ends of tube or conduit services inside the walls of buildings, as a guard against moisture and injury.
2. Terminated at a properly placed doublepole house cut-out.
3. Of specially insulated conductors after leaving the tube or conduit, and separated by at least 10 inches, until the double-pole cut-out is reached.
Wires should be so placed that in the event of the failure or deterioration of their insulating covering the conductors will still remain insulated.
At the entrance of every building there shall be a double-pole switch placed in the service conductors, whereby the current may be entirely cut off. Conductors—Must not be:
1. Of sizes smaller than No. 16 B. & S., No. 18 B. W. G., or No. 3 E. S. G.
2. Lead or paraffine covered.
3. Covered with soft rubber tube.
4. Laid in molding of any kind in damp places.
5. Laid in moldings with open grooves against the wall or ceiling.
G. Laid in molding where less than half an inch of solid insulation is between parallel wires, and between wires and walls or ceilings.
7. Inside conductors must not be laid in plaster, cement, or similar finish without an exterior metallic protection.
Cleatwork is not desirable, and cleats must not be used unless—
1. In a very dry place.
2. In a place perfectly open for inspection at any time.
3. They are porcelain, or well seasoned wood, filled, to prevent absorption of moisture.
4. They are so arranged that wires of opposite polarity, with a difference of potential of 150 volts or less, will be kept at least two and one-half inches apart, and that where a higher voltage is used, this distance be increased proportionately.
5. There is a backing provided, of wood at least half an inch thick, well seasoned and filled, to prevent absorption of moisture. Metal Staples must never be used to fasten
1. Provided with an insulating sleeve or saddle rigidly attached to the metal of the staple, and having such strength and surface as to prevent mechanical injury to the insulation of the conductor.
2. Under conditions in which cleatwork would be acceptable, or where driven into a molding specially adapted for open work.
Wherever conductors cross gas, water, or other metallic pipes, or any other conductors or conducting material (except arc light wires), they should be separated therefrom by some continuous non-conductor at least one inch. In crossing arc light wires the low-tension conductors must be placed at a distance of at least six inches. In wet places an air space must be left between conductors and pipes in crossing, and the former must be run in such a way that they cannot come in contact witli the pipe accidentally. Wires should be run over all pipes upon which condensed moisture is likely to gather, or which by leakage might cause trouble on a circuit.
In rooms where inflammable gases exist the incandescent lamp and socket must be inclosed in a vapor-tight globe. This is not understood to include rooms where illuminating gases are used in the ordinary manner.
In breweries, stables, dye-houses, paper and pulp mills, or other buildings specially liable to moisture, all conductors, except where used for pendants, must be:
1. Separated at least six inches.
2. Provided with a durable moisture-proof covering.
3. Supported by porcelain or glass insulators.
Moisture-proof and non-inflammable tubing may be accepted in lieu ol such construction.
No switches or fusible cut-outs will be allowed in such places. Interior Conduits—Must not be:
2. Of such material or construction that will be injured by plaster or cement, or other