A case may arise where there is electric light on the same chandelier as the gas lights, and that an insulating bushing has been screwed in between the fixture and the pipe. In this case it will be necessary to run two wires to each burner, the pipe common return being now unavailable. Another scheme is to interpose an insulating bushing under each burner; then the second or return wire need only be run from the burner to the gas pipe outside the main bushing. But the local fire-insurance rules must first be consulted.
Most ceiling gas fixtures will admit of the fixture wire being run inside the brass shell, which makes a neater job. But the very best of insulation must be used, and great care be taken that it be not abraded. It should be shellacked or otherwise insulated before use. The electric-light fixture wires are admirable for use here if there is room.
For concealed work in a finished house, locate the position of the fixture under the floor of the room above by measuring both in the room where the fixture is and in the room above. Then cut out a piece of the floor, drill up from underneath through the fixture plaster-rose with a fine drill, and push the fixture wire up. The main wire can be laid under the carpet, or along the floor-crack in the upstairs room.
In wiring up wall-fixtures, push-buttons, etc., it is often possible to fish the wire up from the floor by punching a hole at the fixture and inserting a piece of chain (made for the purpose), attached to a long and stout thread. Then drill into the skirting near the floor plumb underneath the first hole and fish for the chain with a piece of wire having a hook on the end of it. Where fixtures have brass rosettes, these can be removed by (generally) unscrewing the fixture, but first shut off the gas at the meter, or plug the hole; this may seem unnecessary advice, but experience warrants its being given. When the chain is fished out, a piece of wire can be attached to the thread and pulled through in turn. In most cases its point of exit at the fixture can be concealed by the rosette, through a hole in which it passes. Take care that the edges of this hole do not cut the insulation. Care must be taken at every step in gas-lighting wiring.
In wiring up a push-button, screw all wires tightly under their respective binding screws, and then cover wherever possible with adhesive tape. As the wires must be somewhat loose to allow of the connections being made at the back of the push-button at the wall, they will have to be carefully pushed into the hole, and if they are not tightly held by screws, trouble will result. It is a good plan, when using fine enough wire, to make a sort of eye at the end of the wire and pass the screw through this, instead of merely giving the wire end a turn around the screw and then driving the screw home. Of course washers should be used wherever an ordinary screw holds a bare wire.
Automatic Burner Operated by Door.
One of the uses to which an automatic burner can be put is in conjunction with an electric door-spring, lighting when the door is opened, but preferably extinguished by independent push. In this case, a form of trip spring should be used which would only make contact during a portion of the travel of door. Such a trip is shown in Fig. 26.
A is automatic burner; C, the primary coil; B, the battery; T, a swinging trip piece of brass hinged in brass plate, P, which is screwed over the door in such manner that the door opening in direction of the arrow will cause the trip T to strike against the spring S, and make contact. This spring is insulated from the plate P by the hard rubber block R.
On the door being opened, the trip will make contact long enough to light the burner and will then fall back as the door passes. On shutting the door, the trip will be raised and will fall as the door passes, but will not make contact. Or, if so desired, it can be made to operate a second contact to extinguish the burner by fixing a second insulated spring so it will be pressed when the top of trip makes a downward movement—as when the door passes it in shutting.