MEPworx Wiring – How to set up a 20A Ring Circuit

by Simon Brown

A typical question submitted to Customer Support is: can you advise if there is there a provision within the program for entering a Ring Final Circuit but using a 20A protective device, instead of a 32A breaker. As used for the standard 32A Ring final circuit, which is described in Regulation 433.1.204.

It is quite straightforward to set up a non-standard Ring Circuit using a 16A, 20A or 25A breaker as detailed below.

In this example of setting up a 20A Ring Circuit, because the CPD/breaker is of a different rating than the standard 32A, this Circuit Type becomes a ‘Special Socket’ circuit, as opposed to a ‘Standard Socket’ circuit.

To set up a 20A Ring Circuit, please follow the steps below.

1. In the Final board select the SPN Way you wish to use and select the ‘Way Type’ as ‘Special Sockets’ (SO), instead of the ‘Standard Sockets’ (SRi).
    

2. In the Load details, you can select the ‘Point Entry’ as ‘Other’ (at the bottom of the pull-down list) and for this circuit, set the load value as 20A. 
   Also, if you un-check the box for ‘Use Diversity from Board’, you now have the option to enter your own Diversity value.

                                                      
   
   Please note, as this circuit type is still a ‘Socket Circuit’, the RCD requirements of Regulation 411.3.3 still apply. If you have a ‘Risk Assessment’ or ‘Exemption Notice’, you can check the box, ‘Reg.411.3. RCD Exemption’ to remove the RCD requirement from this circuit.
    

3. Next, to set up the cable details.
   For the circuit length, enter the Length as the distance from the Way in the board, to the furthest point of the ring circuit. i.e. half the total distance around the ring circuit. Set it up as Parallel x2 and check the box for 434.4.l-lll, so we only have a single CPD on this circuit and not a CPD per conductor, as per the recommendations of Appendix 10.
   
   
   
   While in the Detailed Cable entry dialog, click on ‘Distance’ and set the Distance Ratio to 67% (⅔), leaving the CPC length the same as the entered circuit length.
    
4. Still in Final Circuit mode, the entered details of the circuit can be easily checked and confirmed by reviewing the circuit’s details in the Final Circuit Schedules.
   
   
   
   Here you can see; the Circuit Type as Special Sockets (SO), the paralleled conductors & CPC, plus the selected CPD rating 
    

The above procedure will enable you to set up a non-standard Ring circuit with the rating of CPD and load value you require.