Discuss Garage supply in the UK Electrical Forum area at ElectriciansForums.net
Thank you, I thought the same but just making sure ??Depends on the cable type and how it is run.
If it is SWA then the earthed armour means no need for RCD protection for that cable.
Flexishield is a similar idea, but the aluminium foil layer has a modest limit for any MCB so it can safely disconnect.
If it is any other cable type it has to be such that it can't realistically be penetrated by accident, so not buried less than 50mm from any surface, and where outside either protected by duct/conduit or run in a manner where it is safe from any realistic risk of damage from gardening activities, etc.
Just to add, you might have a non-RCD side (no 30mA instant RCD) but with a 100mA delay RCD incomer in a TT system.
So yes, it could be a little more complicated...
It would be OK for SWA cables, etc, that don't normally need RCD, as it would allow a cable fault to disconnect the supply even though the TT earth is not low enough impedance to trip the sub-main OCPD.Was just about to ask if upfront 100mA time delayed RCD would be considered suitable protection on a TT installation?
Wouldn't the additional protection requirement then apply after the 100mA delay RCD, therefore additional 30mA RCD's will be required.
The OP said they have a garage CU with RCD there, so I would be going for a MCB (or switch-fuse) to feed SWA so only the one 30mA "additional protection" RCD to trip/reset, and near where it is used.Let's assume a TT installation where all circuits are afforded 30mA protected by RCBOs, with upfront time delayed 100mA RCCB providing additional protection. Would it be better to:
A) Protect armoured run to via MCB, with RCBO board at outbuilding end.
or
B) Protect armoured run with RCBO and use MCB protection at outbuilding?
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