• Not sure how that pic turned out but new installation on TT system. 4pole 100mA S RCD as incomer and a clatter of standard single pole 30mA RCBOs for final circuits along with MCBs.

    Design by contractor.

  • Looking at all the 3P MCBs, I presume that discrimination on earth faults, or per-circuit isolation, isn't a priority for the customer.

    How does the double/reinforced insulation before the incomer look? (or is there an upstream RCD?)

       - Andy.

  • Customer would have no idea Andy, nor would it seem has the contractor. My view is a blatant disregard for 314.1, a regulation that is often swept under the carpet. Likely not a significant safety consideration but a real PITA for the client should the main RCD jump out. Twelve forecourt pumps fed from one of the 3P MCBs via an adjacent board. Oh and a 100mA RCD at intake some 20m away, no time delay and no overcurrent protection other than the DNO service head. The earth loop socket is wired correctly at least. 
    Caveat Emptor and all that but perhaps clients will eventually realise contractors don’t usually make good designers!

  • Lyledunn,

    Seeing far too much of similar installations, Im sure the installation certificate didnt mention any ommissions or deviations? But somebody would have signed for the installation as being compliant with regs, and also the APEA/EI "Blue Book" if its a filling station forecourt and again if the appropriate petroleum storage electrical certificates were issued again who signed it? What did they list as proving competence with regards statute regulations? End user/duty holder should be asking questions for sure.


  • IMHO that installation complies with 314.1, but not 314.2.

  • Both 314.1 and 314.2 do not appear to have been considered. MCBs following an MCB provides zero selectivity. I assume that the Ze is very low due to a lot of buried metalwork and tanks, but even so the upfront RCD probably ought to be a suitable adjustable MCCB, and each pump fed from a separate RCD (or RCBO if available) for touch protection. Not a good or compliant design.