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RCCB & Switch Overload Protection (536.4.202)

sparkiemike
Just trying to get my head around regulation 536.4.202, particularly the last line.


“However overload protection shall not solely be based on the use of diversity factors of the downstream circuits. To achieve overload protection of RCCBs or switches, the rated current of the OCPD shall be selected according to the manufacturers instructions”.


If I understand it correctly in a the sum of the downstream MCBs should not exceed the current rating of the RCD. So in most dual RCD split load boards the RCDs would need to be rated at 100A


Is this correct, because there seem to be a lot of "pre-populated" boards still being sold with 63A RCDs? 


How are others interpreting this new reg?
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  • 0
    The attached BEAMA document shows two methods to determine the sizes, shown also in the Hager document along with more diagrams. 


    The tech dept. of a leading manufacturer told me a few weeks ago that they still provide what could be undersized RCCB's in CU's (undersized if having a lower rating than the upstream OCPD and the sum of the cb's exceeds the RCCB rating) because they supply what suppliers/wholesalers ask for, rather than base sizes on the two methods. The simplest thing to do is as Hager say, make them all 100A.


    F
    attachments.zip
Reply
  • 0
    The attached BEAMA document shows two methods to determine the sizes, shown also in the Hager document along with more diagrams. 


    The tech dept. of a leading manufacturer told me a few weeks ago that they still provide what could be undersized RCCB's in CU's (undersized if having a lower rating than the upstream OCPD and the sum of the cb's exceeds the RCCB rating) because they supply what suppliers/wholesalers ask for, rather than base sizes on the two methods. The simplest thing to do is as Hager say, make them all 100A.


    F
    attachments.zip
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