a.
A 10 microsecond by 1000 microsecond waveform with a peak voltage
of 1500 volts and a peak current of 60 amperes.
b.
An 8 microsecond by 20 microsecond wave form with a peak voltage
of 1000 volts and a peak current of 500 amperes. Do not use fuses
for surge protection.
2.7
FIRE ALARM SYSTEM POWER SUPPLY
Provide dc power supply consisting of rectifier/battery charger, battery
power supply, necessary transformers, and inverters, in the central alarm
receiving location [and in each fire station] as indicated. Provide two
sources of electrical power for each box circuit, [dispatch circuit,] and
alarm transmitting or receiving device, including fire station equipment
requiring local power for operation. Power supply shall conform to [NFPA
1221 for Form 4A] [NFPA 72 for primary and secondary power supplies for
Central Supervising Station].
2.7.1
AC Power
Obtain power from the line side of the main electrical service to each
building. At the location indicated, provide a circuit disconnecting means
in a locked cabinet with the function clearly and permanently identified.
Provide circuit protection in each ungrounded conductor located in a locked
cabinet immediately adjacent to the point of connection to light and power
conductors.
2.7.2
Rectifier/Charger
Supply each rectifier/charger through an isolating transformer taking
energy from a circuit not exceeding 240 volts. Rectifier/charger leads
shall fuse at not less than one ampere and at not more than 200 percent of
the maximum connected load. Rectifier/charger shall be a fully automatic,
variable rate, filtered battery charger capable of providing 150 percent of
the connected battery load. Adjust charger in accordance with the battery
manufacturer's recommendations to provide full "float" voltage to
compensate for the load and maintain the batteries at full voltage. Charger
shall be properly fused and shall incorporate a dc voltmeter and dc
ammeter. [Provide a manual high-rate-of-charge switch together with a red
pilot light to indicate when batteries have been manually placed on high
charging rate.]
2.7.3
Batteries
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NOTE: Nickel-cadmium batteries should not be
specified over lead-calcium type unless some unusual
environmental or operational condition warrants the
additional cost of nickel-cadmium. For normal
installations, battery selection may be left as a
contractor's option. Ensure battery room or
location has adequate ventilation to keep hydrogen
concentrations below 3 percent.
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Provide [sealed,] wet-cell, [lead-acid (lead antimony)] [or] [lead-calcium]
type, adequate to provide each transmitter with a minimum of 24-hour
standby capacity. Mount batteries [on racks] [in cabinets] designed for
SECTION 13851N
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