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Do you install fire alarm systems?

Chris Pearson
Bit of thread drift going on elsewhere, so I have started a new one.


"Do you install fire alarm systems?" - a question which is asked on insurance renewal, but what does it mean?


IMHO, there is a world of difference between providing a mains supply with third core for linking for a couple of smoke detectors and a heat detector in the kitchen on the one hand (i.e. the minimum grade D2 LD3); and a full on panel with separate detectors and sounder etc. (grade A LD2) in a large house. I consider myself perfectly capable of providing the former, but have never attempted the latter.


So where does the threshold lie? I'd be interested in views on certification too please.
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    The earth is so that the panel can flag a wire to earth fault if cabling insulation is mechanically damaged- a  positive to earth fault or a negative to earth fault means the cable has been spiked, but the rest of the self test to see the terminator resistor may still pass.


     


    As I see it the earth (C.P.C.) wire and "tin foil" are used with FP200 cable just because they are  integral to the cable. The fire alarm panel will detect a fault if a nail is driven through a cable even if it is not earthed, in these cases.


    1. Broken positive conductor.


    2. Broken negative conductor.


    3. Short between the two above.


    Earth NOT needed in all three cases.


    The cable only carries 24 Volts at a tiny current. And all components are made of plastic. Earth not needed.


    Perhaps the screen protects the cables from strong magnetic fields or radio interference. I am not really sure on that.


    Z.


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    The earth is so that the panel can flag a wire to earth fault if cabling insulation is mechanically damaged- a  positive to earth fault or a negative to earth fault means the cable has been spiked, but the rest of the self test to see the terminator resistor may still pass.


     


    As I see it the earth (C.P.C.) wire and "tin foil" are used with FP200 cable just because they are  integral to the cable. The fire alarm panel will detect a fault if a nail is driven through a cable even if it is not earthed, in these cases.


    1. Broken positive conductor.


    2. Broken negative conductor.


    3. Short between the two above.


    Earth NOT needed in all three cases.


    The cable only carries 24 Volts at a tiny current. And all components are made of plastic. Earth not needed.


    Perhaps the screen protects the cables from strong magnetic fields or radio interference. I am not really sure on that.


    Z.


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