Test Options in L-PE mode:
In L-PE mode the MFT1800 series offer 3 types of loop test:
3Lo – A 3-wire low current loop impedance test. This test requires all three connections.
Where to use:
For making L-E measurements on circuits where all three conductors are available AND the Phase – Earth circuit is
RCD protected. Requires all three test leads to be connected.
2Hi – A 2-wire high current test. A fast 3-4 second test using high test currents.
Where to use:
On ALL circuits except Phase – Earth measurements on RCD protected circuits.
2Lo – A 2-Wire low current loop test for L-E measurements where the 3rd conductor in not available.
Where to use:
On RCD protected circuits where access to all three conductors is not possible
NOTE : 2Lo is not available when all three leads are connected, as the 3Lo is the preferred
measurement mode.
Selecting the test mode:
To switch between Loop test modes press the Function button, as below:
The test mode is displayed as below:
Default mode 1st Press 2nd Press
NOTE : RCDs can still trip when performing a “non-trip” loop test if there is an existing high level of fault
current flowing in the Earth conductor, or the RCD is not operating within specification
www.megger.com MFT1800 series
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Loop impedance testing
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