3x 2.5mm in MCB


Any issues with 3x 2.5mm cables in an MCB?

MCB feeds 3 socket radials. I don’t see any issue with loading etc, however is there any regulation / guide that prohibits this many single conductors in a single MCB?

I am sure spurs from MCBs on ring finals are allowed, so I am thinking this is fine as long as they are secured correctly.


  • if all are well seated and survive a 'tug test' then there is no real problem,  however if due to the design of the terminals it will not hold - and I have had that with a mix of diameters converging on a clamp terminal-  then the quick fix is one of the wago type things nearby.  But if that extra part can be avoided, that is best.Certainly no reg, against it unless makers instructions explicitly say something, and I'd be most surprised if they did.


  • Thanks and I agree, doesn’t make sense to use wago connectors inside of the DB when the MCB provides an adequate connection.

  • If two are all right, why not three?

    Surely nobody would think twice about several CPCs in a terminal in a back box or accessory.

    The obvious thing is that the MCB needs to be rated for one circuit and not the three summed together.

  • Hello Vantech.

    3 x 2.5mm in one MCB terminal is fine, all things being equal re good workmanship etc. It's covered in Electrical Safety First "Guidance for Installers when Making Connections in Consumer Units," page 9.


                   Colin Jenkins.

  • More important than E.S.F. is BS7671.  Appendix 15A, while only informative, states regarding ring circuits: 

    "An unfused spur may be connected to the origin of the circuit in the distribution box".

    Can that be done without having three conductors in an MCB?