FIRE DETECTION SYSTEM PLACED IN SAN FRANCISCO DRILL TOWER
Signal Sending Equipment Governed by Thermopile of Seven Couples— Installations Found Satisfactory
IN order that all members of the San Francisco Fire Department may become thoroughly familiar with the operation of fire detection service (Reichel system) a local company has cooperated with the San Francisco Fire Department by installing a complete model fire detection system in the fire drill tower. This system is an automatic electrical fire alarm system which automatically detects a fire at its start and transmits a signal to the municipal fire department. There are a number of these systems now in operation in San Francisco therefore the model installation in the fire drill tower will be used in demonstrating its operation to the members f the fire department during the regular course of instructions given in all equipment pertaining to the fire department at the fire drill tower. It will also be used in making demonstrations during the regular San Francisco college course.
The essential unit of this system is the device that is installed on the ceiling (approximately one to each 400 square feet or less) throughout the building, which detects the fire and is called a detector. The arrows at “A” “A” show the two detectors that have been installed in the demonstration model in the fire drill tower. This detector is an electric thermopile, consisting of seven couples (one stud of the couple being bismuth and the other stud antimony). One end of these couples is exposed and the other end is imbedded in a porcelain base so that the heated air cannot come in direct contact with the imbedded ends. When a fire occurs, the heat rising to the ceiling comes in contact with the exposed ends, heating them, while the imbedded ends are not affected. In this manner the two ends of the couples are at a different temperature thereby setting up a flow of electricity within itself.
The detectors are connected together in a series circuit, by wires which in turn are connected to a contact relay located in the main control unit and shown by arrow “B”. The normal position of the needle of the contact relay is on the left hand side of the dial, but a supervising current from a battery is introduced into this circuit with enough current flowing to hold the needle in the center position on the dial. (A close up of this dial and needle is shown in photo No. 2.) Should a wire break, a battery become weak, or anything happen in the circuit so that this supervisory current will not flow, the needle will then deflect to the left hand side of the scale, making a contact which causes a trouble signal to be transmitted to the Municipal fire alarm central station.
Should a fire occur, the heat from it would create a generation within the detector, causing the needle to deflect to the right hand side of the dial. A contact will be made when the needle deflects to the extreme right which will trip relays and cause a fire signal to be transmitted to the municipal fire alarm central station. The fire alarm operator will not send the fire department on receiving a trouble signal but will notify the manufacturer’s office in San Francisco, and this company will send a trouble man. After restoring the system to a normal operating condition, the “trouble man” will then report to the municipal fire alarm central station as a matter of record.
In order to demonstrate just how a fire in a building effects the detectors, a copper cow bell shaped device housing a Majestic heating element has been provided. This heating device by means of an extension cord is connected to the regular 110 volt outlet of the fire drill tower. Then the man in charge of the demonstration holds the bell shaped heating device under one of the detectors, until the heat causes the detector to act just as it would if a fire occurred in a building equipped with the fire detection system. The fire alarm is received and recorded on the fire department tape register installed on the same floor of the fire drill tower.
The model installed in the fire drill tower is equipped with an instrument cabinet containing but one contact relay as shown at “B”. However in a building where there are several floors or areas necessitating a circuit of more than fifty detectors to each floor or area, there will have to be more than one contact relay. These contact relays will be grouped together in one control unit or instrument cabinet, and each one is marked in such a manner as to designate the particular area of floor which each circuit covers. This control unit is usually located inside of the building at a point where it can be seen from the street through a door or window. A small buzzer is located on the top of the control unit or instrument cabinet to notify the subscriber that something has caused a portion of the fire alarm system to become inoperative. The subscriber can then call the company notifying them of the existing condition. This is a check on the fire department central station operators and assures prompt service.
On each circuit there is one contact relay. Also there is one manually operated fire alarm box connected to each circuit, as shown at “C”. This manual box can be pulled to call the fire department making the Fire Detection Service a manual as well as an automatic fire alarm system. This iron manual box is of the usual type of break glass cover aver a pull handle, and is usually located near points of exit or entrance to a plant equipped with this system.
The system within the building is connected to the municipal fire alarm lines by mechanical means within the Master Street Box (shown at ”D”), usually located on a pole or pedestal in front of the building. This street box is of the type used by municipalities on their own fire alarm system, being a non-interfering, successive type of box. Thus this street box brings added protection to the vicinity for it brings another fire alarm box to the neighborhood which can be pulled to call the fire department for a fire in that vicinity. This box can be pulled without disturbing the installation within the building, thereby leaving the system within the building ready to function in case of a fire existing therein.
The arrow at “E” shows the local alarm horn or siren which is usually located on the outside of the building at a point directly over the opening (door or window) from which the control unit can be seen. This horn will operate whenever the system inside of the building has operated for fire. The horn will not blow when the street box on the outside of the building has been pulled. The purpose of this horn is to attract the firemen to the point where the control unit can be seen as well as notifying the occupants of the existing fire in their building. A break glass horn switch is located on the side of the control unit to allow the firemen to stop the horn from sounding after their arrival.
When the property is so large or occupational noise intense then additional horns or gongs are installed.
A storage battery G is used to furnish the electrical energy to keep the main wires, relays, etc. under constant electrical test or supervision and to operate the local alarms and devices used to trip the master street transmitter.
A connection is made to the 110-volt main light or power switch to supply the small current necessary to charge the storage batteries. This connection or tap on the 110 volt power system is made through a separate switch and fuse contained in a red steel box located close to the main light or power switch, with wires in separate steel conduit from this box to the larger steel cabinet containing the storage batteries and battery charging device.
The storage battery has sufficient capacity to operate the system for seven days with the 110-volt power disconnected. Temporary stopping then starting of the 110-volt current does not affect the automatic charging device used.
Wires from the instrument cabinet, or control unit, to the outside of the building, to the storage battery and to the local alarm signal are installed in separate steel conduits.
A casual inspection of the dials of the circuit relays in the Control Cabinet, will disclose the condition of each circuit and circuit battery. However, the storage batteries are examined and tested and a general inspection given all parts of the system.
Also, the inspectors go over the entire property to note any conditions such as goods or materials piled too close to detectors, obstructions in front of manual boxes, etc. and to learn whether any building alterations, or erection of new partitions or walls has shut off protection or introduced new confined area that would not properly be protected by the system.
Since 1913 (the year in which the first fire detection system was installed on the Pacific coast) the City Fire Departments have been notified of fire on the subscriber’s property by this device, so quickly that it enabled response in 92 per cent of fires in time to extinguish them with first aid devices. In only 8 per cent of fires has any hose water been turned into any building using this service.