GAI-Tronics 785-002 24 V DC Explosion-proof Page/Party Handset Stations - Manual (Page 2)

Pub. 42004-157E
Model 780/785-002 and 7805/7855-002 24 V DC Explosion-proof Handset Stations Page 2 of 13
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Installation
Whether installing an entire system or only an add-on station, consult the 24 V dc system layout diagrams
at the end of this manual. These figures, used in conjunction with the station installation information and
the cable layout guide, should provide all the information necessary to install the Page/Party
® stations.
These figures do not show an explosion-proof station; however, the basic points of the system layout and
design still apply.
NOTE
A separate power feed is recommended for Page/Party ® stations in Div.1 areas. With a
separate power feed, the Page/Party ® stations can be shut off for maintenance without disrupting the
power supply to the other equipment in the Div. 1 area.
In 24-volt systems, plan on several branch lines from the dc source with no more than six stations per
branch. One branch could span up to 4,000 feet for a single station. The Maximum Cable Distance Table
lists the limits. Where two or more stations are listed, the assumption is that they are evenly spaced along
the cable.
Each amplifier contains two fuses on the PCBA in the 24 V dc input to protect and isolate the handset and
speaker amplifier circuitry in the event of a failure. Power line wiring to each amplifier or group of
amplifiers should have a fuse or circuit breaker to protect against wiring failures.
If cable with No. 14 AWG power line conductors is used, a 15-amp fuse or circuit breaker should be
installed for each branch line at the point it connects to the battery. Fuse or circuit breaker rating is
determined by the size cable used in the branch. Consult the National Electrical Code (NFPA70) or
Canadian Standards Association (CSA 22.1) for the maximum allowable capacity of the wire used.
The GAI-Tronics 24 V dc series of Page/Party ® system equipment is designed to operate from a 24 volt
dc rechargeable battery. A battery charger can be connected to the battery to maintain the charge.
CAUTION
Under NO condition should this equipment be operated from a battery
charger without the batteries connected.
Most chargers have an unloaded output of 35 to 45 volts that can quickly damage the equipment designed
for nominal 24 volts. To maintain a proper state of battery charge, the voltage across the batteries will be
somewhat greater than 24 volts, but should never exceed 28.8 V dc. Grounding the negative side of the
battery system at only one point is recommended and will ensure hum- and noise-free operation.
Enclosure Placement
All GAI-Tronics Page/Party ® units are wired in parallel. Good system layout design minimizes the cable
required for each installation. GAI-Tronics multi-conductor cable, designed especially for this
application, is recommended. The number, size, and color-coding of conductors are listed in the
accompanying system connection diagrams.
System layout and power cable length are important considerations when installing Page/Party ®
equipment. Consult the Maximum Cable Distance table for typical cable lengths. The cable distance
between stations as well as total cable distance must be considered. Cable distance is more strictly
regulated in 24 V dc systems because of the amount of resistance these cables encounter—the longer the
cable distance, the greater the resistance and IR losses (voltage drop) encountered.