Alarm internal fuse

Discussion in 'Electricians' Talk' started by Toffee1972, May 29, 2007.

  1. Toffee1972

    Toffee1972 Member

    Can any of the more experienced guys/gals help me out with this one please.

    I updated an alarm system over a month ago which consisted of new control panel, remote keypads and bell box. Customer wanted to keep her existing PIR's to keep the cost down.

    I installed the system and did the usual commisioning inc walk test etc. and everything was fine.

    Customer called this weekend and said her alarm had started going off for no apparent reason. When I went to have a look the internal PIR fuse has blown. The fuse was the correct rating for the board.

    Has anybody else come across this before or is it nothing to worry about?

    Any advice would be much appreciated.
     
  2. unphased

    unphased Screwfix Select

    Has the customer been decorating and removed the PIR "temporarily" before putting it back? If messing around with wires without isolating the panel and they short it will blow the fuse. I can't think of any other reason why the fuse would blow. Has to be a short.

    UP
     
  3. Toffee1972

    Toffee1972 Member

    I thought the exact same thing, but no the customer has not touched a thing.
     
  4. unphased

    unphased Screwfix Select



    Lesson to be learned. If the customer insisted that you re-use the existing PIR's then they cannot expect you to guarantee that they work. Tell them that you must charge them for all visits and stuff in connection with the "old" PIR's and even recommend replacing them. Would you agree?

    UP
     
  5. RMH

    RMH New Member

    Whilst "upgrading the alarm" did you replace the existing cable? there is a possibility that some of it runs under carpets etc and if old could be crushed, stapled etc. I once had a hell of a time finding an intermittant short on a RKP fuse. turned out that on the original install the installer whacked a staple through the cable and it would short + & - when someone stepped on a particular floorboard a certain way!
     
  6. Toffee1972

    Toffee1972 Member

    Whilst "upgrading the alarm" did you replace the
    existing cable? there is a possibility that some of
    it runs under carpets etc and if old could be
    crushed, stapled etc. I once had a hell of a time
    finding an intermittant short on a RKP fuse. turned
    out that on the original install the installer
    whacked a staple through the cable and it would short
    + & - when someone stepped on a particular floorboard
    a certain way!

    No I didn't install new cabling.

    If thats the case, its gonna be fun finding that one.
     
  7. X

    X New Member

    If thats the case, its gonna be fun finding that one.

    Hint..

    Fuse each pir +ve feed separately
     
  8. Toffee1972

    Toffee1972 Member

    If thats the case, its gonna be fun finding that
    one.

    Hint..

    Fuse each pir +ve feed separately

    Sorry can you explain in more detail please X?
     
  9. X

    X New Member

  10. Toffee1972

    Toffee1972 Member

    Oh, now I get ya.

    So when the fault does reoccur, it will only trip the appropriate fuse.

    This will still trigger the alarm though, but excellent idea X, cheers
     
  11. unphased

    unphased Screwfix Select

    Toffee

    I'm puzzled by this. Just thinking. Were you asked to change the alarm panel and the bell box because this was happening previously (?) and although you have done as requested (because the owner thought thats what the cause was but it isn't) and you are now saddled with finding the real cause for the false alarms? Possibility me thinks.

    UP
     
  12. Toffee1972

    Toffee1972 Member

    The old panel required an 8 digit number to activate it and was a very old system (late 70's me thinks)

    When I went to power up the old alarm, nothing happened, so I presumed the electronic board inside had gone.
     
  13. X

    X New Member

    This will still trigger the alarm though,

    Indeed... but at least the next step will be straight forward
     
  14. RMH

    RMH New Member

    "At the panel if there is enough room, remove each + pir supply and reconnect it via a fuse & holder (maybe something like 500ma)"

    If you are going to just seperate the PIR feeds then 500mA is a little to high, a standard PIR will only draw around 20-40mA in standby and around 50mA in alarm so I would drop the fuse rating down a tad.
    Great idea though!
     
  15. fooman

    fooman New Member

    The old panel required an 8 digit number to activate
    it and was a very old system (late 70's me think

    needed changing its hard enough remembering my cashpoint 4 digit number :^O
     

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