jpadie Posted February 18 Share Posted February 18 Hello I am adding a new circuit from the main consumer unit to a garden room. The garden room will have its own consumer unit with surge protection. Current plan is that all the circuits in the garden room will be behind rcbos. The connecting cable will be swa and routed mainly underground save for a small part by the main distribution board (clipped and then through a masonry wall) and another by the garden room (behind the external cladding then through thick PIR). I'm concerned that the swa is not protected by RCD type device so was wondering whether it was permitted to put the circuit behind an RCD/RCBO on the main distribution board. I realise that any earth fault in the garden room will trip probably at least two protective devices. Link to comment Share on other sites More sharing options...
FuerteStu Posted February 18 Share Posted February 18 It's common for swas to be only protected by an mcb. If you were paranoid about it, you could put it on a 100ma rcd so you wouldn't get upstream nuisance tripping, but if the cable is fixed securely and glanded off cleanly I don't think you need to worry about it. Link to comment Share on other sites More sharing options...
jpadie Posted February 19 Author Share Posted February 19 Thank you. Link to comment Share on other sites More sharing options...
Onoff Posted February 20 Share Posted February 20 On 18/02/2024 at 19:24, FuerteStu said: It's common for swas to be only protected by an mcb. If you were paranoid about it, you could put it on a 100ma rcd so you wouldn't get upstream nuisance tripping, but if the cable is fixed securely and glanded off cleanly I don't think you need to worry about it. The 100mA RCD at the house end, feeding the swa to the garden room needs to be time delayed to allow for selectivity. I've done this on a TT system but also incorporated a switched fused for overcurrent protection. I took one of these: https://www.internet-electrical.co.uk/switchgear/switchfuses/lewden-single-phase-switchfuse/lewden-fs6380100-white-metal-single-phase-switch-fuse-with-63a-80a-100a-fuses-for-domestic-installations-ip40-100a?gad_source=1&gclid=EAIaIQobChMI59qb_Lq5hAMVuJlQBh0q-wetEAQYASABEgKcr_D_BwE The swapped out the DP isolator for one of these: https://www.ledbulbs.co.uk/products/lewden-100a-100ma-2p-2-module-rccb-100-100-2sa?variant=39691026628666&gad_source=1&gclid=EAIaIQobChMI2IPbuLu5hAMVl5tQBh2QSgQOEAQYAiABEgJUV_D_BwE The SWA goes from their to the new consumer unit in the outbuilding. Link to comment Share on other sites More sharing options...
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