RCD Tripping Times.docx

Table 1 of this article gives the maximum tripping times for the most commonly used types of RCD at residual currents of 1 I∆n, 2 I∆n and 5 I∆n, as specified in the relevant British Standards. It can readily be appreciated from Table 1 that when verifying t he operation of the RCDs listed in the table within disconnection times of 0.2 s, 0.4 s, 1 s or 5 s, either a 1 I∆n test or a 5 I∆n test is always suitable. For example, a 1 I∆n test is suitable suit able for verifying the operation of: . A BS 4293 or BS 7288 non delay RCD within a disconnection time of 0.2s, and . Any non delay RCD referred to in Table 1 within a disconnection time of 0.4s or 1s o r 5s. A 5 I∆n test is suitable for verifying the operation o peration of (for example): . Any delay type RCD referred to in Table 1 within a disconnection time of 1s or 5s, and . A BS EN 61008-1 or BS EN 61009-1 non delay RCD within a disconnection time of 0.2s.

Table 1: Tripping times for RCDs at residual curre nts of 1 I∆n, 2 I∆n and 5 I∆n

RCD type British Standard Trip time At 1 I∆n At 2 I∆n At 5 I∆n

Non-delay (general) BS EN 61008-1 (RCCBs) BS EN 61009 1 (RCBOs) Within 300 ms Within 150 ms Within 40 ms

BS 4293 (RCCBs) BS 7288 (SRCDs) Within 200 ms − Within 40 ms Delay BS EN 61008-1 (RCCBs) BS EN 61009 1 (RCBOs) ( RCBOs) Within 500 ms Within 200 ms Within 150 ms

BS 4293 (RCCBs) Between 200 ms +50% of time delay and 200ms +100% of time delay − Between 40ms +50% of time delay and 40ms +100% of time delay

Note: A 0.5 I∆n test should also be carried out, to check for unwanted tripping.

Additional protection (supplementary protection against direct contact) An RCD used for additional protection must have a rated residual operating current (I∆n) (I∆n ) not exceeding 30mA and an operating time not exceeding 40ms at a residual current of 5 I∆n (Regulation 415.1.1 of the 17th Edition refers).