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    How to Troubleshoot Hard-wired Alarm Systems

    How to Troubleshoot Hard-wired Alarm Systems

    This article describes the procedures for identifying and rectifying commonly occurring faults in Intruder Alarm Systems. The procedures apply to hard wired systems and in the main to close loop type installations as opposed to EOL wired systems.


    In general, alarm hardware components are very reliable and, as such, faults are usually caused by poor installation practices. Listed below are some common faults and the method of detecting their cause and remedy.

    When installing the alarm, the cable connections are the most common source of faults.

    When connecting cables, ALWAYS:

    • Ensure that all the strands of the cable core are seated in or under the terminal and that the terminal screw is fastened securely - lightly tug the wire. Do not over tighten the terminal screws - they can cut through the wire.
    • Wind the cable core around terminal screws in the direction that the screw tightens i.e. clockwise as viewed from the top of the screw.
    • Ensure that there are no spare pieces of the fine core wire lying around the terminal block.
    • Connect cables using terminal blocks - wires twisted together will eventually oxidise and lose the connection.


    And NEVER:

    • Put stripped cable in your mouth or in water before fitting into a terminal block. The core will corrode quite quickly.
    • Run cables under carpets or wooden flooring where it will be walked over. The cable will eventually disintegrate.


    Power Supply Faults

    The 'Power Light' is not lit when the mains power is switched on. The panel works OK on the internal battery.One of the fuses in the supply has blown.WARNING Always isolate the mains supply before working on it. Check the fuses starting at the control panel and work back towards the consumer unit. Always replace fuses with the correct rating. If the fuse blows repeatedly or the circuit breaker repeatedly trips check that the connections are correct. Brown-live, Blue - neutral, Green/Yellow - earth.
    The connection from the transformer in the control panel to the PCB is not present or is not making the connection.Check that the two wires are connected to the correct terminals on the PCB. Remove and reconnect if required.
    The control panel does not work on the internal battery alone.The battery has exceeded its useful life - batteries should last up to 5 years, but like car batteries will not last forever.Fit a new battery.
    The battery fuse (where fitted) on the PCB has blown - this is normally caused by allowing the battery wires to short together.Fit one of the wires to the Battery and then replace the fuse with one of the correct rating. Then connect the other battery lead.


    Control Panel Faults

    The 'Tamper Light' will not extinguish.One or more Personal Attack devices has not been reset,Reset the device(s) and then reset the panel. Note; some control panels have a dedicated PA indication.
    The control panel lid is not fitted or is not tripping the tamper switch in the panel.Check that the lid is properly seated - refit as necessary. If it is properly seated, check that the internal tamper switch is operating correctly - remove the panel lid and locate the tamper switch, then manually hold the switch in its closed position and reset the panel, If the tamper light extinguishes then the tamper switch operating device needs adjusting. If it is of the lever type then the lever should be gently bent such that it operates when the lid is fitted. If it is of the spring type then the spring can be gently extended until it operates correctly or a small packing piece can be attached to the inside of the lid where the spring impinges.
    There is a fault in one of the tamper circuits.There are two tamper circuits - the global tamper circuit through which all the tamper circuits are wired in a closed loop, and the bell tamper circuit. To check the Global Tamper, remove the two wires and fit a link between the terminals; if the fault clears then the fault lies in the global tamper circuit. If, as is likely, there is more than one tamper circuit looped through the global tamper circuit, then each circuit can be checked for 'open circuit' either with a multimeter or by connecting individual circuits into the tamper terminals until the faulty circuit is found. The tamper connections on the circuit can then be checked and rectified as required.

    If the tamper fault is in the bell circuit, then check that the connections are correct according to the wiring scheme, and that the connections are sound. Also check that the bell fuse is OK (this does not normally cause a tamper fault, but can cause strange things to happen. If all appears OK then the fault is in the cable. The easiest way to check this is to wire the sounder temporarily using a new piece of cable, if the sounder works OK then the cable to the sounder should be replaced, If the temporary wiring to the sounder does not clear the fault then the sounder or panel is faulty. In our experience it is usually the sounder, but the only way to check this is to fit a new sounder.

    The panel will not set due to one or more of the zone lights remaining lit. Note, the entry/exit zone and any zone set as intermediate will temporarily light as they are passed through. Note, the alarm can be set by omitting the offending zone(s) as a temporary measure.There are detectors on the zone(s) at fault or there is a fault in the wiring.Check that all detectors are in their normally closed state, i.e. doors are properly closed, and the contacts are fixed in position. If they appear OK then open the control panel and fit a link across the zone terminals; if the fault clears then there is some kind of fault on the zone. If the fault does not clear then the control panel is faulty. If there are unused zones available on the panel then the zone can be rewired into that zone, and the offending zone permanently omitted. If there are no available zones then the zone can be looped into one of the working zones and again the offending zone permanently omitted.
    The alarm goes off immediately on entering the building.The zone through which the entry is made is not set as an entry/exit zone.Either set the zone as entry/exit or ensure that the zone is not used for entering the building.
    The entry time is set too short.Extend the entry time.
    A detector on the route from the entry door to the control panel is not set to intermediate mode. Detectors in intermediate mode will not trigger the alarm provided that entry is made by the entry/exit route.Set the zone to intermediate mode.
    There is no power supplied to the powered detectors. (PIRs and shock/vibration detectors are powered from the panel's 12v AUX supply.)The power supply from the panel is protected by a fuse which has 'blown'.Renew the fuse with one of the correct rating. Note; if the fuse 'blows' repeatedly then there is probably a short in the cabling to the detectors.


    Sounder Faults

    The sounder does not operate when an alarm is signalled. Note; depending on the control panel, the external sounder may not sound when a tamper fault occurs with the alarm in the 'unset' state, but the internal sounder will sound.The bell fuse has 'blown'.Renew the fuse.
    There is a fault in the cabling to the sounder.Check the connection scheme to ensure that the correct colour cores are connected to the correct terminals. If necessary, temporarily connect the sounder with a new piece of cable. If the fault persists fit a new sounder.
    The sounder set-up routine has not been carried out - some sounders require a link to be fitted or removed for the sounder to work correctly.Return the sounder to its factory set configuration and then carefully follow the set-up procedure.
    The sounder does not operate on its internal battery. (if all power to the sounder is removed, i.e. the mains supply to the panel and the battery in the panel, the sounder should sound using its integral rechargeable battery.)The internal battery has exceeded its useful life.Renew the battery or replace the sounder with a new unit.


    Detector Faults

    If one or more of the zones on the system are showing permanent faults, the cabling and detectors on that circuit will have to be tested. Depending on the complexity of the cabling system and the position of any joints, it may be possible to test parts of the circuit with more than one detector, thus isolating the part of the circuit with the fault.

    A magnetic contact is not going 'closed circuit' when it is in proximity to its magnet.The switch and magnet are not close enough. Note; also check that the door or window with the contact fitted is closing properly and does not move excessively in draughts etc.Move the magnet/switch combination closer to each other.
    The switch is faulty. Note; this is quite common - the switch can be damaged by suffering heavy knocks.Replace the switch part of the detector.
    The wiring at the terminals has corroded or become disconnected.Remove the switch and check the wiring. If there is evidence of corrosion, shorten the cable by a few centimetres and remake the connection. Note; contacts on external doors can get damp through the door, ideally, contacts should be fitted at the top of doors. If the door is very damp at the bottom, the contact is best moved to the top of the door. A small amount of electrical grease or silicone can be used to protect the connection.
    The PIR does not operate. The walk test LED does not come on.There is no power supply to the unit.Check that there is a 12v supply to the unit. If there isn't check the fuse in the control panel, if the Fuse is OK then there is a wiring fault, if so temporarily connect the unit to the 12v supply from the panel to confirm that the wiring is at fault.
    The PIR walk test LED operates but the unit does not trigger an alarm.There is a fault in the wiring to the unit, either a short causing the detector to appear closed circuit or the unit has not been looped into the zone circuit correctly.Check the connections at the control panel and PIR. If necessary temporarily wire the unit directly to the control panel to test that the unit operates correctly.
    The unit does not detect movement of hot bodies within the protected area.The unit is pointing in the wrong direction.Check that the PCB in the PIR is set in the correct position for its mounting height. Adjust the angle of the PIR to cover the area.
    The room temperature is too high. PIRs rely on a temperature difference between the ambient and that of a hot body in motion; in conservatories and kitchens/bathrooms the temperatures may be very similar.The best remedy is to use a dual technology detector (PIR & Microwave).


    Intermittent Faults

    These are by their very nature difficult to find and rectify. Usual suspects are as follows:

    • Poorly fitting doors which move in heavy draughts.
    • PIRs fitted over radiators, pointing at boilers or other heat sources. Note; radiators warm up too slowly to be detected by PIRs pointed at them, but the thermals rising from them can cause PIRs to trigger. PIRs will not normally be fitted such that direct sunlight impinges upon them, but reflected sunlight (e.g. glass coffee table) or glass roofed conservatories can trigger them.
    • Insects in PIRs, Spiders and ants walking across the lens inside the PIR will trigger them. The remedy is to block all holes using silicone or tape.
    • Cables running under carpets in walked on areas.
    • Cable joints sited in damp areas, or poorly made joints.

    This Article is Copyright and cannot be used commercially without express written consent of Sapphire Alarms. Illegal copies are detected by Copysentry
    2013-06-17 12:01:44

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