RCD Testing

28 March 2022

Chapter - 64 (Initial Verification)

This chapter defines the testing required on completion of an installation, to verify that the requirements of BS7671 have been met prior to being placed into service.

Amendments to Section 643.7 & 643.8, have further clarified the requirements for testing RCDs within an installation as below:

Regulation 643.7
Protection by automatic disconnection of the supply

Previously, effectiveness for 643.7 was verified by testing in accordance with Table 3A in appendix 3. This table has now been deleted.

The new regulations for verification of RCDs within TN and TT systems are as follows:

Compliance with Regulation 411.4 (TN Systems) & 411.5 (TT Systems) shall be verified by:

(2) verification of the characteristics and/or the effectiveness of the associated protective device. This verification shall be made:

For RCDs by visual inspection and testing.

The effectiveness of automatic disconnection of supply by RCD’s shall be verified using suitable test equipment according to BS EN 61557-6 (see Regulation 643.1) to confirm that the relevant requirements of Chapter 41 are met, taking into account the operating characteristics of the device.

NOTE: Regardless of RCD Type, effectiveness is deemed to have been verified where an RCD disconnects within the time stated below with an alternating current test at rated residual operating current (IΔn)

  • For general non-delay type, 300ms maximum
  • For delay ‘S’ type RCD, between 130ms minimum and 500ms maximum
Regulation 634.8 additional protection

Previously, effectiveness under 634.8 was verified where the RCD disconnects within 40ms when tested at a current equal to or higher than
five times its rated residual operating current.

This has now been aligned with 634.7 and the new regulations are as follows:

The verification of the effectiveness of the measures applied for additional protection is fulfilled by visual inspection and testing. Where RCDs are required for additional protection, the effectiveness of automatic disconnection of supply by RCD’s shall be verified using suitable test
equipment according to BS EN 61557-6 (see Regulations 643.1) to confirm that the relevant requirements of Chapter 41 are met.

NOTE: Regardless of RCD Type, effectiveness is deemed to have been verified where an RCD disconnects within the time stated below with an alternating current tested at rated residual operating current (IΔn):

for general non delay type, 300ms maximum.

Overview

The revised text in both clauses align the requirements for both regulations which now state that the only testing required for general non-time delayed RCDs, is to be carried out using an alternating current at the rated residual operating current.

Therefore, the only test required regardless of the Type of RCD (AC, A, F & B), it is only required to test under the “AC” parameters of the RCD, with the Test current set at 1IΔn, with a maximum disconnection time of 300ms.

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