FIRE ALARM SYSTEMS

FIRE ALARM SYSTEMS

In a report to the National Fire Protection Association on “fire alarm systems,” Ralph Sweetland says:

“Especial importance should be placed upon the necessity of designing, installing and maintaining municipal fire alarm systems so that alarms may at all times and under the most adverse conditions be promptly transmitted to the fire departments. To this end attention is called to the supreme desirability of providing headquarters, which, as far as practicable, will be free from liability of damage by fire, either by internal or external causes; of installing apparatus which may promptly and correctly transmit alarms, but which will be simple and easy of maintenance; of placing all wires outside of buildings, as far as practicable underground; of having frequent and systematic tests of all apparatus, and of having in charge of such systems only men of known judgment and ability. These rules cover requirements for the construction and installation of appliances most commonly used at the present time. Any other types of apparatus which are judged to have merit should be submitted for examination and test and, if found efficient, will receive recognition accordingly.

(Note.—The portion of these rules relating to the design and construction of appliances are -but a partial outline of requirements. A device which fulfills the conditions herein outlined, and no more, will not necessarily be acceptable. Samples of all appliances should be submitted to the Underwriters’ Laboratories for examination and report before being introduced for use.)

MANUALLY OPERATED FIRE ALARM SYSTEMS.

(For cities having a population of more than 100.000.)

Systems requiring operators in headquarters for the transmission of alarms.

  1. (1.) Headquarters.
    1. (a) The building to he of fireproof construction. Note.—No wood should he permitted in the construction, even for top flooring, window or door trim, closets, instrument cases, etc.
    2. (b) The building should preferably be located so as to be unexposed for a distance of at least 150 feet. If so located as to he exposed, then especial attention should be given to guard against damage from such exposure by protection of exposed openings, of so constructing roof as to resist damage which might be caused by falling walls. Note.—Tt is desirable to locate the building in a park or public square, where the conditions as regards exposure can he fully met. As the building, even for a large city need not be large, and since for a slight increase in cost it can he made artistic in appearance, objections to such locations should not be insurmountable.
    3. (c) The building should he used for no other purpose than that relating to the fire alarm service.
    4. (d) One approved three-gallon chemical fire extinguisher and six sand pails to be provided for each 2,500 square feet of floor area., When any fiortion of the building is occupied as a stable, garage, machine shop or for storage purposes used in connection with the un-keep of the system. the part thus occupied to he protected by an approved system of automatic sprinklers.
    5. (e) Approved registers and tappers speeded for “fast” time to he provided, on which box signals may he received. Approved time and automatic dating stamps by which time of receipt of alarms may be recorded also to be provided.
    6. (f) An approved transmitter, speeded for “fast” time to be provided, by means of which alarms may he sent to the fire department houses by automatically repeating from box circuits, subject to the control of manually-operated interlocking switches.
    7. (g) An approved manually-operated transmitter, speeded for both “fast” and “slow” time, to be provided, by means of which alarms may he sent over the “slow” time circuits to the fire department houses: also sounded on outside hells and whistles, if any, and arranged so that it may. if desired, be run at “fast” time and control the tapner circuit.
    8. (h) There must be means provided for telegraph communication from central office over each box circuit, and there must he telegraph keys at central office by which signals may be sent, both over each alarm circuit separately, and also over all “fast time circuits simultaneously, and qver all “slow” time circuits simultaneously.
    9. (i) An independent reserve source of energy of proper capacity constantly available to bo provided. The following sources of energy are given in their order of preference: (1) Storage batteries; (2) motor generators or rotary transformers.
    10. (j) Approved heavy current protectors to he provided near the point of entrance of wires or cables into the building.
    11. (k) Approved automatic devices to be provided, by means of which grounds or openings of circuits will be immediately announced by visual and audible signals. Manual tests of ail circuits to be made at least four times during each 24 hours, a record of all tests being filed for reference.
    12. (l) Approved slate or marble switchboards to be provided, on which shall be mounted the various switches, relays, protectors, etc. Switchboards should he located so as to be readily accessible from all sides.
    13. (m) Plans of all outside circuits and records of all tests to be kept on file.
    14. (n) To have at least two (2) competent on duty constantly, and in addition linemen to available so that in case of derangement of side circuits prompt attention can he given same.
  2. (2) Boxes.—
    1. (a) To be of an improved keyless, non-interfering and successive type. Note.— Boxes may be of the key type, if key is properly attached to box.
    2. (b) To be located so as to suitably protect the city. Note.—No definite rules can be given for the location of boxes. In general, it is considered that from any building in the mercantile and manufacturing districts it should not be necessary to traverse over 300 feet in order to reach a box; in closely built-up residential districts ibis distance should not he over 500 feet.
    3. (c) Circuits to he so arranged that not more than 20 boxes will he on any circuit, and no apparatus other than boxes to he connected on box circuits outside of fire alarm headquarters. Note. —It is desirable to so arrange circuits that adjacent boxes will he on different circuits. It is rec ommended that all circuits he brought to easily accessible terminals, mounted on slate or marble bases for testing purposes.
    4. (d) The placing of municipal boxes inside of buildings should be discouraged as far as possible, and where private boxes arc used, they should he conveniently located on the outside of buildings. Note.—When located inside of buildings, must be mounted on filled hardwood blocks not less than inches in thickness: the supports of blocks and of the boxes must be independent of each other.
  3. (3) Wiring. Note.—To secure the largest measure of safety and efficiency in the operation of municipal fire alarm systems, all wires outside of buildings should be placed under ground
    1. (a) Must under normal conditions employ only closed metallic circuits.
    2. (b) Aerial wires should have an approved insulating covering, to be equivalent in conductivity and tensile strength to No. 10 galvanized iron when single wires are used, and to No. 16 B. & S. hard-drawn copper wire where cables are used.
    3. (c) Aerial wires to he supported entirely on glass or porcelain petticoat insulators at least every 50 feet: run as far as possible under rather than over electric lii’ht or power wires, and especial attention should he given to preventing liability to accidental contact with such wires.
    4. (d) Wires and cables inside headquarters to have approved insulated covering and to he so supported that they will he as free as possible from liability of grounds or mechanical injury.
    5. (e) Wires inside fire department houses have anproved insulating covering, to he supported in conduit, in armored cable, or on noncombustible non-absorptive insulators, and so arranged that the insulating covering will come contact with no other substances than the designed supports, the protecting bushings and the connecting instruments.
  4. (4) Fire Department Houses,
    1. (a) An approved perforating register and 6-inch gong for the “fast” time service to be provided by means of which alarms may be received.
    2. (b) An approved 15-inch electro-mechanical gong for the “slow” time service to be provided, by means of which alarms may he received.

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