MORLEY-IAS ZXa, Руководство по вводу в эксплуатацию, Страница: 51 / 55

MORLEY-IAS ZXa / Zxe
C
OMMISSIONING
M
ANUAL
Page 46
Document No.996-071, Revision: 1 , Aug 99
16 Supplementary Information
16.1 Locating Earth Faults
•
The control panel continually checks the wiring to determine if any external wiring has become short circuit to
earth.
•
An indication of an earth fault is given by amber LEDs on the panel front. The earth point is normally maintained
at 1V above the battery -ve terminal. The polarity of the fault will be indicated with a “-ve” or “+ve” sign on the
alphanumeric display.
•
For example:
For service phone 123 4567890
EARTH FAULT TO –VE ON EXTERNAL WIRING
•
The panel will normally continue to work with a single earth fault on the system. The fault, however, should be
rectified as soon as possible.
Locating the Earth fault
•
Most earth faults are found by performing resistance measurements on the cables before connecting them to the
panel.
•
Earth faults can appear on the following external cables :
1. Sounder circuit wiring
2. Detector circuit loop wiring
3. Auxiliary 24V output feed.
•
It is also possible to use a dc voltmeter in conjunction with a working panel to find out which circuit is shorted to
earth. This is particularly useful if the fault is past a loop isolator as this type of fault can often not be detected by
a resistance check at the end of the loop.
•
The following method describes how to locate this fault by disconnecting the external wiring.
1. Measure the voltage from the battery negative input to the supply board earth input. On a healthy system,
this will read approximately 1V.
2. If the voltage is less than 0.3V, the panel will register an earth fault to negative.
3. If the voltage is more than 1.5V, the panel will register an earth fault to positive.
4. Each of the external cables can be disconnected in turn while monitoring this voltage. As soon as the
faulty wiring is disconnected, the voltage will return to 1V. This identifies which cable is shorted to earth.
Please take great care not to disconnect any of the internal board to board connections
while the panel is powered up, otherwise damage may be caused to the circuits!