• TT system, the disconnection time of 0.2 s might not be achieved at I_Δn and therefore the disconnection time should to relate to 5I_Δn (if, as per the Note to 643.7.1 states, we take into account the operating characteristics of the device per Table 3A in Appendix 3) - that is unless your tester has a 2I_Δn setting

On the other hand it would be rather odd to specify a test that couldn't necessarily physically be performed in a compliant installation. For a 30mA RCD, BS 7671 specifies a max Zs of 1667 Ohms (table 41.5) (or thereabouts - actually is is permitted to be higher provided R_A doesn't exceed that figure (but I'll ignore that for the moment), the 200Ω figure is only a suggestion) - thus the maximum earth fault current we can really rely on is 230V/1667Ω = 138mA - i.e. below the 150mA needed for a 5x test. (Or if the tester has some means of generating the extra current, the touch voltage would exceed 50V which would likely abort the test anyway).


I guess this is all a results of the discussion about removing RCD testing from the 18th - it does seem peculiar though to record the result of a test if you're not recording an indication of which test was performed.


  - Andy.

• TT system, the disconnection time of 0.2 s might not be achieved at I_Δn and therefore the disconnection time should to relate to 5I_Δn (if, as per the Note to 643.7.1 states, we take into account the operating characteristics of the device per Table 3A in Appendix 3) - that is unless your tester has a 2I_Δn setting

On the other hand it would be rather odd to specify a test that couldn't necessarily physically be performed in a compliant installation. For a 30mA RCD, BS 7671 specifies a max Zs of 1667 Ohms (table 41.5) (or thereabouts - actually is is permitted to be higher provided R_A doesn't exceed that figure (but I'll ignore that for the moment), the 200Ω figure is only a suggestion) - thus the maximum earth fault current we can really rely on is 230V/1667Ω = 138mA - i.e. below the 150mA needed for a 5x test. (Or if the tester has some means of generating the extra current, the touch voltage would exceed 50V which would likely abort the test anyway).


I guess this is all a results of the discussion about removing RCD testing from the 18th - it does seem peculiar though to record the result of a test if you're not recording an indication of which test was performed.


  - Andy.