Cooper TP Workshop Manual_Scant:Layout 1 7/8 ... - Cooper Security

8136 Fitting a PSU2. If faults are still present then split the IDIS loop into three or four smallersections. Try each section in turn, reinitialising each time. (Allow formissing zones). See if you can isolate the faults to one section of theloop. If a section cannot be driven alone from the panel because of itsphysical location then use the Handheld Programmer with a local powersupply to test that section.3. Once you have found a faulty section of the loop then check the currentreadings of each module (see Table 4). Try isolating n-wire modulesfrom their contacts and sensors (link the tamper and alarm loops asthough the contacts are closed). If this fixes the problem then look forground faults in the contact wiring.4. If you still cannot find a specific fault then break the loop into smallersections and repeat the checking.5. Once you have all sections of the loop working correctly as individualsections then reconnect all of them to the panel and reinitialise. If thecomplete loop still does not work properly then the fault is most likelydue to capacitance loading or ground fault.6. Isolate the whole loop from the panel and check for connection betweenthe loop 0V wire and ground. There should be no connection.7. Split the loop into two approximately equal sections, with at least somesensors in each section. Connect one section at a time and reinitialise.If the system works with either section but not both it has a capacitanceloading problem.Improving the Voltage DropYou can improve the voltage drop by: thickening the 0V wire, reducing thecurrent drawn by different sensors, or adding remote power supplies.Use thicker cable for the 0V wire. Standard alarm cable has a resistance ofthe order of 10 Ohms per 100 metres per core. For example: five typical relayPIRs, each drawing 25mA, connected to the end of a 100 metre length ofcable produce a voltage drop along the 0V wire of approximately 1.2V.Doubling up the 0V wire reduces the drop to 0.6V - a more acceptable level.You can thicken the cable selectively. Six PIRs at the end of 50 metres ofcable causes more voltage drop than one PIR at the end of 100 metres.Taking care during system layout can prevent such problems arising.Reducing current consumption. At all costs avoid intermittent heavy loadssuch as sounders taking their supply via the IDIS 0V wires.Fitting a PSULocal PSU(s) can be added at intermediate points of an IDIS loop. The +vefeed from the panel can be totally disconnected from the IDIS bus or used topower a few more local sensors with the remote PSU powering the rest. SeeFigure 14.496339 Issue 4 37 of 44