Notifier ID50 Installation, Commissioning & Configuration Manual page 32

ID50 Series Panel - Installation, Commissioning & Configuration Manual
The loop wiring MUST
be disconnected from
the panel during this
procedure
997-263, Issue 4
September 2002
4.4.1 Loop Wiring
Typical connections of analogue addressable loop pair
to a loop are shown below.
Note: The total length of the communications loop pair
cannot exceed 1200 metres using 1.5mm
Checks Before Connection
To check the Loop wiring:
1 Link out any isolators on the Loop by temporarily
shorting terminals 2 and 4 on each isolator. The
following tests should then be carried out using a low-
voltage multimeter.
2 Check the continuity of each leg of the loop and
measure the end-to-end resistance. Verify that the total
loop resistance (sum of both legs) is less than
40 ohms.
3 Connect the meter in ‘normal’ polarity (+ve to loop
+ve and -ve to loop -ve). The meter should initially
read low resistance but this should increase as the
capacitor in each of the loop devices charges. If the
meter indicates the presence of a forward-biased
diode then it is probable that one or more of the loop
devices is connected in reversed polarity or the wiring
is crossed.
4 If reversed device(s) are indicated in step 3, they may
be located by successive halving of the loop (if the
site layout makes this difficult, the affected section of
the loop can be identified from the panel fault
messages after the system has been configured and
the links in the isolators removed).
Note:
a. A = Normally open switch - closes under an alarm
condition.
b. To comply with the requirements of EN54, isolators
should be fitted between a maximum of 32 loop
devices. For the ID50 Series Panel, do not place more
than 25 loop devices between isolators (20 if FET
isolators are used).
26
cable.
2