Consumer units in new and modern domestic installations should contain Residual Current Devices ‘RCDs’ as well as circuit breakers. Either as combined RCD/circuit breaker devices ‘RCBOs’ which can get a bit expensive or alternatively and less expensive through the use of split load boards with usually two RCCBs protecting multiple circuit breakers.
Since January 2016 and the introduction of Amendment 3 to the 17th Edition of BS7671…
All domestic consumer units must be made of a non-combustible material or enclosed in a cabinet made of a non-combustible material.
The layout of a split load consumer unit – the supply enters the unit via the double pole Main Switch which can be used to isolate the consumer unit/installation. From the out going side of main switch we have a Line and Neutral supply to the incoming side of each RCCB which in turn connects to the neutral bars and supplies the individual circuit breakers via the copper busbar at the bottom.
Things to note. The current rating on the Main Switch usually 100A is not the ‘tripping current’ of the device – as it offers no overload protection. The rating represents the safe switching current of the device only. Also on the RCBOs the current rating of usually 80A or 63A is also just the switching capacity of the device and the 30mA is the ‘tripping’ current of this RCD device.
Completed cosumer units should also have any blanks in place where needed and there should be no holes in the front, bottom or sides that are big enough to stick a finger in. On the top of the consumer unit there should be no holes larger than 1mm in diameter after completion. Stickers informing of the RCD test procedure should be in place as should any inspection and testing notices.