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4 Types of Tests Conducted on Internal Electrical Installations

4 Types of Tests conducted on Internal Electrical Installations

Internal electrical installation of a building consists of cabling and associated accessories such as switches, sockets, distribution boards, and light fittings. Their primary function is to provide illumination and power supply to internal lighting and electrical appliances.

This article explains the tests to be conducted in completed internal electrical installations before commissioning. 

Tests on Internal Electrical Installations

On completion of internal electrical installation, the following tests shall be carried out:

  1. Insulation resistance test
  2. Polarity test of the switch
  3. Earth continuity test
  4. Earth electrode resistance test

The testing shall be carried out for the completed installations in the presence of and to the satisfaction of the engineer-in-charge, and the test results shall be recorded.

1. Insulation Resistance Test

Insulation Resistance Test

2. Polarity Test of Switch 

Polarity Test of Switch 

3. Earth Continuity Test

4. Earth Electrode Resistance Test

R = V/I         

Where,
R = Resistance of the test electrode in ohms,
V = Reading of the voltmeter in volts,
I = Reading of the ammeter in amps.

Earth electrode resistance test

Test Certificate 

Upon completing an electrical installation (or an extension to an installation), a certificate shall be furnished, countersigned by the certified supervisor under whose direct supervision the installation was carried out. This certificate shall be in the prescribed form in addition to the test certificate required by the local electrical supply authorities.

FAQs

Which are the types of tests conducted on internal electrical installations?

The types of tests conducted on internal electrical installations are:
1. Insulation resistance test
2. Polarity test of the switch
3. Earth continuity test
4. Earth electrode resistance test

What is the higher limit of insulation resistance of an internal electrical installation?

The insulation resistance is measured in megaohms and shall not be less than 12.5 megaohms for the wiring with PVC insulated cables, subject to a minimum of 1 megaohm variation.

What is the formula to calculate the resistance of an electrode?

The resistance of the test electrode ‘A’ is given by the formula: 
R = V/I         
Where,
R = resistance of the test electrode in ohms, 
V = Reading of the voltmeter in volts,
I = Reading of the ammeter in amps. 

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