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Three Phase RCD & MCB Wiring?

Nano Brewery
Please could somebody advise on the most cost effective procedure of wiring up RCDs & MCBs on a DIN Rail for independent circuit protection.  Tried Googling to no joy.  Plenty of Single Phase advice, images, videos.  If using 4 Pole MCBs & RCDs, would I be correct in assuming that similar to single phase, it's just a case of Busbar-ing the MCB Lives to the RCD Lives and taking the RCD to Neutral Bar?


Have seen diagrams (like below) where the Incoming L1, L2, L3 get split to separate DP MCBs, RCDs and SP MCBs for each phase.  Seems like a bit of a faff and a pricey option (3x DP MCBs + 3x RCDs + 3x SP MCBs) per circuit.


I have 3x Three Phase Circuits (13A, 40A, 48A) that I wish to protect independently with RCDs.


Thanks in advance!  Dan.

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  • 0
    Cheers Andy.  So it's possible but not normal practice or layout?  Have you ever seen it done?  Or are RCCBs nearly always downstream?  Or a RCBO used?

    Traditionally RCDs have been a bit of a rarity on 3-phase DBs - since they tend to be more industrial so tend to be associated with wiring methods that don't fall foul of the 30mA RCD requirement (for soft sheathed cables embedded in walls etc), don't feed bathrooms and where industrial sockets need an RCD it's often placed at the socket for convenience. There's not really a 3-phase DB equivalent of the "split" CU we see for domestics. The manufacturers will no doubt try to sell you an RCBO, but an MCB in the board with a downstream RCCB will be just as effective and likely cheaper.  At least by using a normal 3-phase DB you get all their type testing for free as it were.


       - Andy.
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  • 0
    Cheers Andy.  So it's possible but not normal practice or layout?  Have you ever seen it done?  Or are RCCBs nearly always downstream?  Or a RCBO used?

    Traditionally RCDs have been a bit of a rarity on 3-phase DBs - since they tend to be more industrial so tend to be associated with wiring methods that don't fall foul of the 30mA RCD requirement (for soft sheathed cables embedded in walls etc), don't feed bathrooms and where industrial sockets need an RCD it's often placed at the socket for convenience. There's not really a 3-phase DB equivalent of the "split" CU we see for domestics. The manufacturers will no doubt try to sell you an RCBO, but an MCB in the board with a downstream RCCB will be just as effective and likely cheaper.  At least by using a normal 3-phase DB you get all their type testing for free as it were.


       - Andy.
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