This is the most important part of any new installation or any work carried out on an existing circuit. The extent a DIYer can inspect and test is very limited as they may not have the necessary expertise and probably won't have access to the relevant test equipment that complies with the current regulations. The 16th Edition Wiring Regulations BS7671:2001 as amended requires that test equipment to fulfill the following criteria:
- Instrument standard is BS EN 61557: Electrical Safety in low voltage distribution systems up to 1000 VAC and 1500 VDC.
- Test leads should conform to HSE Guidance Note GS38
- Basic measurement accuracy of 5% for Digital Equipment and 2% for Analogue Equipment.
- Test equipment should have a calibration check regularly
- BS EN 61557 requires a maximum operating error of 30% of reading over the stated measurement range.
- Resistance testing should be done with a meter with a no load voltage of 4 to 24 volts and a short circuit current of 200mA. The measuring range should cover 0.2 to 2 ohms with a resolution of at least 0.01 ohms for digital equipment.
- Insulation resistance testing with in a domestic environment requires and instrument that can deliver 250 volts for ELV Circuits and 500 volts for LV Circuits. An output current of 1mA at the required test voltage.
- Earth Fault loop impedance test.
- Earth Electrode resistance test
- RCD tests
The above criteria is a BASIC outline of the requirements. The necessary equipment to cover all the required tests cost in excess of £800 which is well outside that which a normal DIYer will want to pay.
