Bosch Building Technologies

    How to Trouble-shoot D125B

    Issue

    When the smoke head is placed on its base, the voltage on the D125B on terminals (7) and (9) drops to 7 volts DC.

    Solution

    Terminal (2) Zone B and Terminal (3) Zone A do not require a 1K ohm end-of-line resistor (EOL) because it is part of the D125B. An unnecessary EOL resistor is likely the cause of the problem.

    To supervise the loops, install an EOL resistor beyond the last detector of each protective loop. If you are replacing a D125 or D125A Module with the D125B, you can use the 1.5k resistor (P/N: 15-03130-000) installed with the original system. If you are installing a D125B in a new system or in an existing system and adding additional devices, use the 1.8k resistor (P/N: 15-03130-006) supplied with the module.

    The D125B shorts the protective loop on the panel when the high (+) and low (-) sides of either module loop are shorted together or when a smoke detector activates.

    With the D9412, D9112, D7412, D7212, D9112B1, and D7212B1 Control Panels, the D125B opens the protective loop on the panel during the following conditions:

    • Either of the module protective loops are opened.
    • The D125B Interface module is not powered.
    • Either the high (+) side of the loop or the low (-) side of the loop is shorted to ground.

    With the G, GV2, GV3, GV4 Series Control Panels, a short to ground causes a ground fault condition when Ground Fault detect is enabled.

    Part numbers D7212B, D9112B, D7212B1, D9112B1, D7212, D7412, D9112, D9124, D9412, D7412G, D9124G, D9412G, D7412GV2, D9124GV2, D9412GV2, D7412GV3, D9412GV3, D7412GV4, D9412GV4, D8112, D8112E, D8112E1, D8112G, D8112G1, D8112G2,

    Version history
    Revision #:
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    Last update:
    ‎05-30-2018 05:30 PM
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