GE Security ZP3, Инструкция по установке и обслуживанию

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ZP3 Fire Control Panel Installation, Commissioning and Maintenance Manual
REV 11 (ISS 08/03/2010) Page 105
Line isolators
Line isolators are devices installed on the Z-Address line to monitor for short circuits on the field
wiring. These devices keep up to 93% of the line operational in the event of a short circuit. Line
isolation can only be utilised when style A wiring is used. They must be installed in accordance
with the requirements of BS5839 Part 1.
Operation
See Figure 65 for a schematic of line isolator usage. Isolators are installed on the loop at intervals.
A short circuit on the loop wiring causes the isolators on each side of the short to disconnect the
damaged section of cable. This removes the short from the loop, allowing the remainder of the
loop to function normally.
Schematic
Figure 65: Line isolator usage schematic
Legend:
Item Description Item Description
1 Control Unit 3 Isolators
2 Detectors
Rules for using line isolators
1. Isolators should be located on the Z-Address loop either at the beginning and end of each
zone, or at regular intervals.
2. To comply with BS5839 Part 1, no more than 1 zone, or 20 detectors or callpoints, must be
grouped between two isolators. Other standards allow up to 32 devices between isolators.
3. A maximum of 16 isolators can be used on each Z-Address loop.
4. The total loop cable resistance must not exceed 75 ohms (37.5 ohms for each positive and
negative leg).
5. The maximum cable resistance between any two isolators, or from the panel to the first
isolator, is 18 ohms for both cores (9 ohms for each positive and negative leg).
6. The Z-Address loop is pulsed at nominal 20-volts Pk-Pk. When loops are installed in
accordance with this Wiring Guide, then the maximum volt-drop across the loop is 4-volts.
This ensures that isolators always receive a supply of at least 16-volts.