Guide to 17th Edition Consumer Units

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Shower Cooker Sockets Sockets Lights Lights Smoke
The following options, each with their own benefits, can be considered by the installation designer.
The Fire detection circuit and the socket outlet circuits share
a common RCD. This may reduce the reliability of the mains
supply to the Fire detection circuit as appliances and portable
equipment are likely causes of RCD tripping.
The cumulative effects of electronic equipment in the
modern home, is such that some current is likely to flow in
the protective conductor. A 30mA RCD will trip between 15-
30mA. This could cause unwanted tripping, regulation 314.1
(iv) refers.
Any fault would result in the loss of all the lighting, this could
in itself cause a hazard and the lack of power to the fridge
/ freezer circuit for example would be very inconvenient.
Regulation 314.1 (i) asks the designer to consider this
eventuality.
Consumer Unit Arrangements
Not Permitted A consumer unit with a 30mA RCD main switch is likely to be unsuitable for 3 main
reasons:
Guide to | 17th Edition Consumer Units 14
“A consumer unit with a 30mA
RCD main switch should not be
used to protect all the circuits”