By David Wren
A typical question submitted to Customer Support is can you advise if there is 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, 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 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:
- 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).
- 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 because this circuit type is a ‘Socket Circuit’, the 18th Ed requirements for RCD protection as in 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 individual circuit. - Next, setting 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. Not a CPD per conductor, as per the recommendations of Appendix 10 for paralleled circuit cables.
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. - 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.
The above procedure will enable you to set up a non-standard Ring circuit with the rating of CPD and load value you require.
Here you can see the Circuit Type confirmed as Special Sockets (SO), the paralleled conductors and CPC (all are x 2), plus the selected CPD rating.