All three phase appliances in Australia are required to be earthed under the Australian Wiring Rules (AS/NZS 3000). Earth continuity testing verifies the integrity of the earth path from the earth pin on the plug all the way to the frame of the appliance, including all exposed bolts, screws, and conductive surfaces.

PTTS performs this via point-to-point probe testing using the Metrel BT3309 PAT tester. A measurement is taken from the earth pin to each accessible conductive part of the machine.

Insulation resistance testing for three phase appliances is substantially more involved than single phase. Testing must be performed at each phase terminal individually against earth (L1-E, L2-E, L3-E) and between each pair of phase terminals (L1-L2, L2-L3, L3-L1), for a minimum of six measurements.

Before performing insulation resistance testing, PTTS ensures the appliance is isolated, capacitors are discharged, and any sensitive electronics are disconnected to prevent damage.

Where it is safe to do so, certain three phase appliances will require clamp or differential earth leakage testing. This test uses a calibrated clamp meter around the earth wire to detect any current present on the earth conductor during normal operation.

The presence of current on the earth wire indicates a leakage path that represents an electric shock risk and must be investigated before the appliance is returned to service.