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Lamps on fixtures, where exposed to dampness, must be surrounded by vaporproof globes, and when exposed to mechanical injury, must be surrounded by globes protected by stout wire guards.
Sockets.—No portion of the lamp socket or lamp base exposed to contact with outside objects shall be allowed to come into electrical contact with either of the conductors.
Wooden mouldings must be made of two pieces, a backing and a capping, so constructed as to thoroughly incase the wire and provide a one-half-inch tongue between the conductors, and a solid backing which, under grooves, shall not be less than threeeighths of an inch in thickness; must be of well-seasoned lumber, and be treated inside and out with at least two coats of white lead or shellac. Where moulding is run over rivets, beams, etc., a backing strip must first be put up and the moulding secured to this. Capping must be secured by brass screws.
Interior conduits must be equipped at every outlet with an approved outlet box; must be continuous from one junction box to another, or to fixtures, and the conduit must properly enter Ul fittings. Conduits must be installed as complete systems without the conductors.
Signal lights must be provided with approved tell-tale board, located preferably in pilot-house, which will immediately indicate a burned-out lamp.
Motors must be thoroughly insulated. Where possible, should be set on base frames made from filled, hard, dry wood and raised above surrounding deck. On hoists and winches they shall be insulated from bed-plates by hard rubber, fiber or similar insulating materials. Shall be covered with a waterproof cover when not in use. Must each be provided with a name-plate giving maker's name, the capacity in volts and amperes and the normal speed in revolutions per minute. Must be wired under the same precautions as with a current of same volume and potential for lighting. The motor and resistance box must be protected by a double-pole cut-out and controlled by a double-pole switch, except in cases where one-quarter horse-power or less is used.
The leads or branch circuits should be designed to carry a current at least fifty per cent greater than that required by the rated capacity of the motor to provide for the inevitable overloading of the motor at times.
Insulation Resistance.—The wiring in any vessel must test free from grounds; i. e., the complete installation must have an insulation between conductors and between all conductors and the ground (not including attachments, sockets, receptacles, etc.) of not less than the following:
Up to 25 amperes 800,000 ohms.
50 •' 400,000
All cut-outs and safety devices in place in the above.
Where lamp sockets, receptacles and electroliers, etc., are connected, one-half of the above will be required.
SIGNALING SYSTEMS (governing wiring for telephone, telegraph, district messenger and call-bell circuits, fire and burglar alarms, and all similar systems).—Outside wires should be run in underground ducts or strung on poles and, as far as possible, kept off of buildings, and must not be placed on the same cross-arm with electric light or power wires. When outside wires are run on same pole with electric light or power wires, the distance between the two inside pins of each cross-arm must not be less than twenty-six inches. All aerial conductors and underground conductors which are directly connected to aerial wires must be provided with some approved protective device, which shall be located as near their point of entrance to the building as possible, and not less than six inches from curtains or other inflammable material. If the protector is placed inside of building, wires, from outside support to binding-posts of protector, shall comply with the following requirements:
1. Must be of copper, and not smaller than No. 16 B. & S. gauge.
2. Must have an approved rubber insulating covering (see No. 41).
3. Must have drip loops in each wire immediately outside the building.
4. Must enter buildings through separate holes sloping upward from the outside; when practicable, holes to be bushed with nonabsorptive, non-combustible insulating tubes extending through their entire length. Where tubing is not practicable, the wires shall be wrapped with two layers of insulating tape.
5. Must be supported on porcelain insulators, so that they will not come in contact with anything other than their designed supports.
6. A separation between wires of at least two and one-half inches must be maintained.
In case of crosses these wires may become a part of a high-voltage circuit, so that similar care to that given high-voltage circuits is needed in placing them. Reliable porcelain bushings at the entrance holes are desirable, and are only waived under adverse conditions, because the state of the art in this type of wiring makes an absolute requirement inadvisable. The ground wire of the protective device shall be run in accordance with the following requirements:
1. Shall be of copper, and not smaller than No. 16 B. & S.
2. Must have an approved rubber insulating covering (see No. 41).
3. Shall run in as straight a line as possible to a good, permanent ground, to be made by connecting to water or gas pipe, preferably water pipe. If gas pipe is used, the connection, in all cases, must be made between the meter and service pipes. In the absence of other good ground, the ground shall be made by means of a metallic plate or bunch of wires buried in permanently moist earth.
In attaching a ground wire to a pipe, it is often difficult to make a thoroughly reliable solder joint. It is better, therefore, where possible, to carefully solder the wire to a brass plug, which may then be firmly screwed into a pipe fitting. Where such joints are made under ground they should be thoroughly painted and taped to prevent corrosion. The protector to be approved must comply with the following requirements:
1. Must be mounted on non-combustible, non-absorptive insulating bases, so designed that when the protector is in place, all parts which may be alive will be thoroughly insulated from the wall holding the protector.
2. Must have the following parts:
A lightning arrester which will operate with a difference of potential between wires of not over 500 volts, and so arranged that the chance of accidental grounding is reduced to a minimum.
A fuse designed to open the circuit in case the wires become crossed with light or power circuits. The fuse must be able to open the circuit without arcing or serious flashing when crossed with any ordinary commercial light or power circuit. A heat coil, if the sensitiveness of the instrument demands it, which will operate before a sneak current can damage the instrument the protector is guarding. Heat coils are necessary in all circuits normally closed through magnet windings, which cannot indefinitely carry a current of at least 5 amperes. The heat coil is designed to warm up and melt out with a current large enough to endanger the instruments if continued for a long time, but so small that it would not blow the fuses ordinarily found necessary for such instruments. These smaller currents are often called “sneak” currents. 3. The fuses must be so placed as to protect the arrester and heat coils, and the protector terminals must be plainly marked “line,” “instrument,” “ground.” Wires beyond the protector, except where bunched, must be neatly arranged and securely fastened in place in a convenient, workmanlike manner. They must not come nearer than six inches to any electric light or power wire in the building-unless incased in approved tubing so secured as to prevent its slipping out of place. The wires would ordinarily be insulated, but the kind of insulation is not specified, as the protector is relied upon to stop all dangerous currents. Porcelain tubing or circular loom conduit may be used for incasing wires where required as above. Wires connected with outside circuits, where bunched together within any building, or inside wires, where laid in conduits or ducts with electric light or power wires, must have fire-resisting coverings, or else must be enclosed in an air-tight tube or duct. It is feared that if a burnable insulation were used, a chance spark might ignite it and cause a serious fire, for many installations contain a large amount of very readily burnable matter. NOTES.—General Suggestions (National Board of Fire Underwriters). In all electric work conductors, however well insulated, should always be treated as bare, to the end that under no conditions, existing or likely to exist, can a grounding cr short circuit occur, and so that all leakage from conductor to conductor, or between conductor and ground, may be reduced to the minimum. In all wiring special attention must be paid to the mechanical execution of the work. Careful and neat running, connecting, soldering, taping of conductors and securing and attaching of fittings, are specially conducive to security and efficiency, and will be strongly insisted on. In laying out an installation, except for constant-current systems, the work should, if possible, be started from a center of distribution, and the switches and cut-outs, controlling and connected with the several branches, be grouped together in a safe and easily accessible place, where they can be readily got at for attention or repairs. The load should be divided as evenly as possible among the branches, and all complicated and unnecessary wiring avoided. The use of wire-ways for rendering concealed wiring permanently accessible is most heartily endorsed and recommended; and this method of accessible concealed construction is advised for general use. Architects are urged, when drawing plans and specifications, to make provision for the channeling and pocketing of buildings for electric light or power wires, and in specifications for electric gas lighting to require a two-wire circuit, whether the building is to be wired for electric lighting or not, so that no part of the gas fixtures or gas piping be allowed to be used for the gas-lighting circuit. Insulation Resistance (National Board of Fire Underwriters).The wiring in any building must test free from grounds; i. e., the complete installation must have an insulation between conductors and between all conductors and the ground (not including attachments, sockets, receptacles, etc.,) of not less than the following: