ZP3 Fire Control Panel Installation, Commissioning and Maintenance Manual
Page 108
REV 11 (ISS 08/03/2010)
Unshielded cable
Unshielded cable should only be used where it is impractical to use shielded cable. An example
would be the upgrading of an existing system to a ZP system, where the cabling already exists.
When the Z-Address Line is used with unshielded cable, the panel should be set to "AVF" mode. In
this mode, some of the functional responses are deliberately slowed, in order to maintain data
integrity in an electrically noisy environment. Electrical noise, generated by third party pulsing
systems, can transfer into Z-Address Lines if the third-party cables are adjacent to the fire alarm
cables.
In some cases use of unshielded cable can cause spurious responses.
CAUTION:
Under no circumstances must an unconnected screen be left floating on a cable. If
screened cables are used they must be terminated as described under
Shielding
on page
106.
Rules for using unshielded cable
1. Z-Address Lines may be run in steel or plastic conduit or trunking, or fixed to walls or supports
without conduit.
2. Third party or mains power cabling may not be run adjacent to the Z-Address line or in the
same conduit or trunking.
3. The cores of multi-core cable may be used for several Z-Address Lines from the same panel,
as well as ZP approved sounders, and ZP Systems DC control lines.
4. Where multi-core cable is used, it must only be used for the ZP fire detection system devices.
Third party cabling should not be run inside the same outer insulation as the fire detection
cable. Examples are Public Address and Intercom Systems. Third party cabling includes
connections between ZP interface units and relays, etc. of other systems.
5. Noise generated by an un-shielded Z-Address Line may cause interference into third-party
systems, such as intercoms.
6. Unshielded Z-Address Lines must be separated from high voltage cables by at least 300 mm,
as per BS5839 Part 1.
7. Unshielded Z-Address lines must be separated from all other cables by at least 50 mm.
Loop length
The Z-Address Line operates with a 2-core loop length of up to 3000 metres when no high power
devices are used on the line. High powered devices, e.g. loop powered sounders, draw more
current and engineering calculation is required for specific line configurations to make sure that
the line resistance through various sections of the line does not cause the line drive voltage at the
end of the line to drop from 20 volts to below the specified detector minimum of 16 volts. For
current draws and minimum line voltages see the applicable datasheets. Refer to Ziton if further
assistance is required.
The Z-Address Line must meet two criteria; resistance and capacitance. The maximum
permissible resistance of a loop is 75 ohms. This is the combined resistance of both conductors.
The total capacitance of a line should not exceed 0.7
F with either leg shorted to earth.
Table 27 gives the conductor sizes required for different loop lengths, which meet the above
criteria when using normal copper screened cable and no loop powered sounders. Lengths for
high capacitance cables should be reduced accordingly.
