OF INTEREST TO VOLUNTEER FIRE DEPARTMENTS

HOW TO ESTIMATE APPROXIMATE COST OF OUTSIDE FIRE ALARM

Amount Necessary for Outside Wire Plant of Municipal Fire Alarm System — Labor Costs for Aerial Work — Materials for Pole Lines*

WHERE an outside wiring system is necessary, it is first important to decide on the location of the fire alarm boxes. To do this, obtain a map of the village and spot the locations of the boxes, keeping in mind the following regulation which is a part of extensive rules issued by the National Fire Protection Association:

“Boxes shall be located so as to suitably protect the city or town. In general, it is considered that a box should be plainly visible from the main entrance of any building in congested districts. In mercantile or manufacturing districts it should not be necessary to travel more than one block, nor more than three hundred feet to reach a box; in closely built-up residential districts this distance should not exceed one block or five hundred feet; in other residential districts, this distance should not exceed three blocks or more than one thousand feet along or toward the main artery of travel.”

In all probability, minor changes will have to be made in the preliminary layout of the boxes. There may be no poles in the neighborhood or no practical way to reach the box location. It is most important that pole locations and numbers be recorded. This simplifies the preparation of specifications, and affords absolute reference points as to box locations, turning points in the line-wire-run and so forth.

The total number of pole line sections in the plant having been determined, the required length of No. 10 B & S triple braid weatherproof hard drawn solid copper wire is readily established, since the average length of a pole line section is 120 feet, allowing for sag, wire ties and so forth.

The quantity of hardware fittings and so forth may be established from the following list which is necessary for each pole.

One cross arm; two 1 1/4 x 1/4 x 28-inch galvanized cross arm braces; two 1 1/4 x 8-inch locust or oak pins (locust pins are better); two No. 19 Hemingway glass insulators; two 1 1/2-inch round galvanized washers; two 2 x 2 x 1/8-inch square galvanized washers; two 5/16 x 4 1/2-inch galvanized carriage bolts; one 1/2 x 16/18 or 20/22-inch machine holts and nuts (length depending upon thickness of pole).

The next step is to ascertain the requirements of the owners of the pole line as to the positions they will assign for fire alarm wires. One company may require the attachment on the first “gain” below the secondary distributing wires; another, at least four feet distant; another requires fire alarm wires below other signal wires and still another will have fire alarm wires at no other place than directly above the other signal wires, that is. telegraph and telephone wires.

It is also necessary to establish the “climbing space” permitted by the owners of the pole line. Some owners permit a climbing space of twenty inches. Others keep to the standard of thirty inches. One large power company in the East requires even forty inches. This is very important since the climbing space establishes the size of the cross arm. Forty inch spacing would mean a special cross arm with corresponding increase in cost.

It is of much importance that these points he settled before starting installations so as to avoid costly rearrangements of wire plant.

Law of Pole Line Permits

In connection with the pole line work, it has been definitely established in the courts that a public service company using the highways as mounting space for its pole structures must permit a municipal corporation to attach its fire alarm and police signal wires without cost. This point of law has been further established to mean that one cross arm or one duct space in an underground subway complies with the requirement. Usually, a municipality, in order to obtain the pole line permits, must enter into an agreement with the public service company issuing such permits, releasing the public service company from all damages arising from the presence of the municipal property on its poles and from any suit for personal damages arising out of injury to a municipal employee while on the pole line or in an underground manhole, and so forth.

If there are any crossings over the right of way of a steam or electric railway, the permission of the owner must be secured, and may be generally obtained through the office of the Engineer-in-Charge, of Maintenance-of-Way. Clearance of the wires will average between thirty to thirty-five feet measured to the top of the rail. For mechanical strength, the wires should he increased to No. 8 B & S at railroad crossings, especially if the span exceeds one hundred feet.

A fair average cost for cross arms made ready by the ground-man and placed in position by the lineman is two dollars an arm. The cost of pulling wire in place, tying to insulator, including minor tree trimming averages Between seventy-five cents to one-dollar a hundred feet. Extensive tree trimming should be treated as special, as it adds to the cost.

These costs are the result of field experience in and around New York and are based on union labor rates prevailing at about the present time.

Loop wires to the box should be No. 14 B & S n. e. c. rubber covered wire. These loop wires must be installed in conduit, and the conduit must be insulated from the ground by means of an insulating joint placed at the fire alarm box. This is of extreme importance otherwise there is much danger of a lineman sustaining injuries—even fatal injury through grounding himself between the wire line and conduit.

* From catalogue of Stanley and Patterson, Inc., New York.

The material required for each box is as follows:

One 1/2-inch service head with 2-hole porcelain cover; 1/2-inch galvanized conduit to reach from wire line to the insulating joint; three 4-inch wood screws and two short nipples cut from 1/2-inch conduit.

The wood screws and nipples are used to attach the box to the pole, in preference to the old type back board or arm method, both of which required cutting the pole. The nipples are used to space the distance between the box and the pole.