7.4.2.1.2 Insulation Resistance and Earth Continuity Checks
If the unit is disassembled to access the internal Micro SD card, then the following
checks must be made after the unit is reassembled and before use.
The unit must be unpowered and electrically isolated from the installation wiring by
removing all connections with the exception of the safety Protective Conductor
Terminal (PCT) connection to the equipment case, which may be left in place.
Ensure that all case fixings have been reinserted and tightened to the correct torque.
Insulation Resistance Check
• Connect the following pins together to form isolation groups on the unit under
test:
H49 Terminal Connections Terminals Isolation Group
Primary Power Supply Input – Slot C 23 and 24 1
Secondary Power Supply Input – Slot B 1 and 2 2
Alarm Relay – Slot A 1,2 and 3 3
• Using an insulation resistance tester and taking care to follow the manufacturer’s
safety precautions, test between the following isolation groups with the output
set to 500 V DC:
Test # First Isolation Group Second Isolation Group
1 Primary Power Supply Input – Group 1
Groups 2 and 3 connected to
Case PCT
2 Secondary Power Supply Input – Group 2
Groups 1 and 3 connected to
Case PCT
3 Alarm Relay – Group 3
Groups 1 and 2 connected to
Case PCT
• Verify that the insulation resistance of each test is >100MΩ.
• If any of the test measurements are <100MΩ then the root cause must be
identified and rectified before the unit can be returned to active service.
Caution:
These tests must only be carried out by a maintenance operative having
appropriate technical training and experience necessary to be aware of hazards
to which that operative may be exposed in performing installation / maintenance
and of measures to reduce the risks to that person or other persons.
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