D-1
Appendix D
Checking System Wiring
Overview This appendix contains instructions on how to use a volt/ohm meter to check system wiring.
Using the Volt/
Ohm Meter
When using the volt/ohm meter to check each circuit, make sure to adhere to the notes and
instructions below.
Note:
• Ensure that no power is applied to the 4100 fire alarm panel and that all wiring is properly connected
(terminal blocks, LED/switch module ribbon cables, etc.).
• Use the green grounding lug in the control panel for all measurements to ground.
• Each circuit must test free of all grounds and extraneous (stray) voltages.
• If there are problems removing all power from the fire alarm system, there is an alternate method of
testing for stray voltage. The wires may be lifted from the panel and terminated with appropriate
resistors. Use 3.3 Kohms across conductor pairs and 50 Kohms from any conductor under test to
ground. All conductors must read less than 1.0V AC or DC.
Use the volt/ohm meter as described in the steps below to check each circuit type.
1. At the control panel, locate wires from each initiating device or indicating appliance circuit.
2. Check each circuit for extraneous voltage by setting the volt/ohm meter to AC. Place the
meter probes so that the black probe is on the “-” wire and the red probe is on the “+” wire.
Meter readings must show less than 1.0 VAC.
3. Set the volt/ohm meter to DC and repeat step 2. The meter must read less than 1.0 VDC.
4. Test all conductors for voltage to ground. The meter must read no more than 1.0V AC or
DC.
5. Set the volt/ohm meter to OHMS and place the meter probes as described in step 2. Check
the circuits using the resistance measurements in Table D-1. Locate and correct any
abnormal conditions at this time.
Note: If the reading indicates an open circuit in an initiating circuit, make sure the smoke
detector heads are properly mounted and seated. The circuit may be open if smoke detector power
is not present, and if separately powered 4-wire devices are used.
6. Check all other system wiring to verify that each circuit is free of grounds and extraneous
voltages.
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