Cable Insulation Test

Probe 1 - Green crocodile clip

Probe 2 - Red crocodile clip

When testing on a fire alarm make sure all devices are removed and the cables are joint

through (most addressable bases work fine however no electronic parts can be attached).

The continuity test is to confirm there are no short/open circuits on the loop. This will also

show a resistance, typically we want under 25Ω.

The insulation resistance test is often referred to as meggering the loop (due to the brand

megger). It involves sending a low current high voltage to stress test the system. We

typically use 500V DC. The rule of thumb for this test is 500mΩ per 500V so we would want

a result of >500Ω, if we did the test at 1000V we would expect a result of greater than 1000

megaohm (>1000Ω)

Cable testing -

Select resistance continuity (Rlo)

Probe 1 to earth 1, probe 2 to earth 2 - test

Probe 1 to live 1, probe 2 to live 2 - test

Probe 1 to neutral 1, probe 2 to neutral 2 - test

Results are low resistance ohms I.e 15.4Ω

Select insulation resistance (Riso)

Twist earth 1 to earth 2

Twist live 1 to live 2

Twist neutral 1 to neutral 2

Probe 1 on earth pair, probe 2 on live - test

Probe 1 on earth pair, probe 2 on neutral - test

Probe 1 on live pair, probe 2 on neutral - test

Results are high megaohms >500 mΩ