Published:
20 May 2010
Category:
Q&A
Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day, concerning final ring circuits and OCPD size, is answered by the ECA:
Question: My scenario is this - I have a caravan park installation in which I wish to install a 16mm 3c SWA ring circuit. My question is, how do I calculate the maximum size of the overcurrent protection device (OCPD) for this circuit?
I have a hunch that the answer should be the OCPD rating x 0.67 (i.e., for a 60A ring circuit, the CCC of the installed cable would only need to be 40A). Is this calculation factor correct? If not, how is it calculated?
Answer: The 0.67 factor is a good rule of thumb.
The main thing is to ensure that the loads are as equally spread around the ring as possible, preferably near the middle and not bunched near the beginning to ensure that no leg is overloaded.
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