Inspection and Testing 127 Table 7.5 RCD Type
Half Rated
Full Trip Current
BS 4293 and BS 7288 sockets BS 4293 with time delay BS EN 61009 or BS EN 61009 RCBO As above, type S with time delay
No trip No trip No trip No trip
Less than 200 ms 1/2 time delay 200 ms 300 ms 130–500 ms
Set the test instrument to the rating of the RCD. Set the test instrument to half-rated trip. Operate the instrument and the RCD should not trip. Set the instrument to deliver the full-rated tripping current of the RCD. 5. Operate the instrument and the RCD should trip out in the required time.
1. 2. 3. 4.
When an RCD is used for additional protection against shock, it must be rated at 30 mA or less and operate within 40 ms when subjected to a tripping current of five times its rating (IΔn). Test instruments have the facility to provide this value of tripping current. There is no point in conducting this ‘fast trip’ test if an RCD has a rating in excess of 30 mA. All RCDs have a built-in test facility in the form of a test button. Operating this test facility creates an artificial out-of-balance condition that causes the device to trip. This only checks the mechanics of the tripping operation, it is not a substitute for the instrument tests. All other items of equipment such as switchgear, controlgear interlocks, etc., must be checked to ensure that they are correctly mounted and adjusted and that they function correctly.