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Obvious departures from the regulations at first glance at a new consumer unit.

Jaymack
I was asked to give an EICR on an domestic property which is to be placed on the market (part P applicable). I found that a builder as part of the other renovation work, (new doors, windows and kitchen etc.) has carried out the installation of a new metal consumer unit. On first opening this dual RCD unit, the 2 lighting circuits were on one R.C.D., and the 2 final ring circuits on the other R.C.D,, it was obvious also, that some wires to the new CB's were short and not lengthened, resulting in a bird's nest at the M.C.B.''s.


Plainly, a qualified electrician hadn't carried out the work. What would the readers as registered electricians have done ?. 1. Walk away. 2. Propose to have an E.I.C.R. carried out (UNSATISFACTORY), then carry out the rectification work and issue MWC's.3. Rectify the obvious departures, issue M.W.C.'s and then issue a SATISFACTORY E.I.C.R. 


Jaymack
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    AJJewsbury:




    Is there a requirement for MCBs to have reducing ratings working away from the RCD? ie, in reverse order: 40, 32 , 32......16,..6, 6  Or just common practice?



    Just good practice as far as I'm aware - if the larger currents involve only the shorter lengths of bus-bar then the overall heating is minimised. Pretty minimal effect in any event I would have thought.


       - Andy.

     




    It's really a little more complicated than that. The order does not necessarily have to be "largest to smallest" - it's important to note that, because of the thermal protective element, breakers, mcb's and RCBOs, just like fuses, get hot. If you have two breakers adjacent with high duty cycle, they may overheat. Putting devices with a low duty cycle (lightly or infrequently loaded circuit) between devices with a high duty cycle (heavily loaded and/or frequently loaded circuit) is the guidance given by most manufacturers of DBOs and CUs.

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  • 0

    AJJewsbury:




    Is there a requirement for MCBs to have reducing ratings working away from the RCD? ie, in reverse order: 40, 32 , 32......16,..6, 6  Or just common practice?



    Just good practice as far as I'm aware - if the larger currents involve only the shorter lengths of bus-bar then the overall heating is minimised. Pretty minimal effect in any event I would have thought.


       - Andy.

     




    It's really a little more complicated than that. The order does not necessarily have to be "largest to smallest" - it's important to note that, because of the thermal protective element, breakers, mcb's and RCBOs, just like fuses, get hot. If you have two breakers adjacent with high duty cycle, they may overheat. Putting devices with a low duty cycle (lightly or infrequently loaded circuit) between devices with a high duty cycle (heavily loaded and/or frequently loaded circuit) is the guidance given by most manufacturers of DBOs and CUs.

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