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Multiple circuits in a single MCB/RCBO

Former Community Member
Former Community Member
Having undertaken some inspections recently I'm finding a lot of older installations with multiple circuits within a single RCBO. Example being 2 light circuits (Upstairs/downstairs) being added to a single B6 RCBO.

The circuit design covers single pendants in each room and some downlights in the kitchen. The majority of bulbs are LED so from a risk point of view would this be unlikely to exceed 6amps. From the EICR however would this be considered C3 in peoples opinions due to risk level with a potential of splitting to separate RCBO's, or should this be C2 as there are technically 2 circuits fed from a single MCB?


Likewise the same installation has a 32amp MCB (RCD protected) supplying a ring final circuit downstairs. When work has been undertaken in the past, an additional radial circuit has been added to the same MCB in 2.5mm T&E. My view on this is that this instantly requires a C2 coding, as the radial circuit feeds multiple sockets (and there is no Fused spur within the radial line) it is not rated for the potential draw and the 32amp breaker will not trip with the overload of the radial line.


There are no spare ways in the board, so am I correct in claiming this would require a new replacement board to accommodate and separate the circuits? Would this be different if the radial only served a single double socket for ease of the wiring?


There appears to be a lot of confusion on when/if its acceptable to add radials to an existing breaker and I wondered if there was any clarity, given that these circuit amendments are historic and retrospective changing to meet current regulations is not essential providing it met previous regulations.


Many thanks

David
Parents
  • 0
    The initial inspection of the switches / pendants indicated some overheating within upstairs and downstairs light points. Evidenced by some nice green ooze at the end of the cables.


    That is not over-heating, it is the polymer in the plastic breaking down slightly. It, generally, isnt a fault, unless it is excessively bad.


    As for a C3 as upstairs and downstairs lighting on one circuit breaker. I'd say no way is that a C3. What real danger is that? What if the downstairs light circuit had tripped, and the Owner had to go in the dark to the kitchen cupboard to reset it - it  would be no different to all the lights tripping, there is always an area that will be dark. If it is such a proble, we woudl eb fitting emergency lighting in domestic premises. In 30+ years, I think Ive fitted 2 emergency lights in houses. It is very unusual to do so, thus proving that there is very little risk in having no lighting in a domestic setting.
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  • 0
    The initial inspection of the switches / pendants indicated some overheating within upstairs and downstairs light points. Evidenced by some nice green ooze at the end of the cables.


    That is not over-heating, it is the polymer in the plastic breaking down slightly. It, generally, isnt a fault, unless it is excessively bad.


    As for a C3 as upstairs and downstairs lighting on one circuit breaker. I'd say no way is that a C3. What real danger is that? What if the downstairs light circuit had tripped, and the Owner had to go in the dark to the kitchen cupboard to reset it - it  would be no different to all the lights tripping, there is always an area that will be dark. If it is such a proble, we woudl eb fitting emergency lighting in domestic premises. In 30+ years, I think Ive fitted 2 emergency lights in houses. It is very unusual to do so, thus proving that there is very little risk in having no lighting in a domestic setting.
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