Electrical Capstone Practical Exam IR Insulation Resistance

Tutorial and tips on fault finding for Insulation Resistance.

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Errors: 8:33 and 8:55 I mention 'Protective' Earthing on RCDs I meant to say 'FUNCTIONAL' Earthing.

Set Megger on 500 V
Any electrically sensitive equipment needs to be tested on 250V. This includes equipment containing surge protective devices connected to earth, EMC Electromagnetic compatibility Filters and other sensitive equipment. You may disconnect Sheathed heating elements or RCD with FE connection (RCBO's).

TEST YOUR VOLTAGE RANGE
This needs to be between -10% to +20%
So on 500V your voltage reading needs to be within 450V to 600V.
How do you test this? Find your 1M ohm resistor tester. Hook up your meggar to test 1M ohm leave this set up and then test voltage with your multimeter to read how many volts are actually going through that 1Mohm resistor. You need to get a reading between 450-600V on a Meggar @500V

INSULATION REISTANCE VALUES
New Installations -Greater than 50M ohm
Existing Installations -Greater than 1M ohm
Heating Elements -Greater than 0.01M ohms
Functional Earthing -Greater than 0.05M ohms