Honeywell Morley-IAS ZX Series Commissioning Manual

Contents

Honeywell Morley-IAS ZX Series Commissioning Manual Manual pdf 59 page image

ZX Fire Alarm Control Panels MORLEY-IASCommissioning Manual Document No. 996-175-000-1, Revision 01 Page 5516 Supplementary Information16.1 Locating Earth Faults• The control panel continually checks the wiring to determine if any external wiring has become shortcircuit to earth.• An indication of an earth fault is given by amber LED Indicators on the panel front. The earth point isnormally maintained at 1V above the battery negative terminal. The polarity of the fault will beindicated with a ‘negative’ or ‘positive’ sign on the alphanumeric display.• For example:EARTH FAULT TO -VE ON EXTERNAL WIRINGFor service phone 123 4567890• 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 connectingthem to the panel.• Earth faults can appear on the following external cables:1. Sounder circuit wiring2. Detector circuit loop wiring3. Auxiliary 24V output feed.• It is also possible to use a dc voltmeter in conjunction with a working panel to find out which circuit isshorted to earth. This is particularly useful if the fault is past a loop isolator, as this type of fault canoften 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 healthysystem, 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 thefaulty wiring is disconnected, the voltage will return to 1V. This identifies which cable is shorted toearth.Please take great care not to disconnect any of the internal board-to-board connectionswhile the panel is powered up, otherwise damage may be caused to the circuits!