Among the chief considerations for the wider use of d.c. circuits in buildings is selection of appropriate protective devices, switchgear, and accessories.

Currently many of the standards for accessories and protective devices currently common in the industry are a.c. only, and products complying solely with those standards may not be suitable for d.c. systems.

Switchgear, plugs and socket outlets used with d.c. systems will be capable of handling and where appropriate suppressing arcing which occurs as plugs are withdrawn or contacts open; this does not occur in a.c. systems as the current-waveform crossing zero helps extinguish arcing.

Type B RCDs are not, generally, available for d.c. systems at present.

High breaking-capacity (HBC) fuses, including suitably-rated fuses to BS 88, are technically a good choice for protecting d.c. circuits. However, in installations such as those for domestic , it has become commonplace to utilise resettable devices such as mcb’s to help mitigate the risks that might arise from the lack of training and specific knowledge of persons in the premises.

It is clear that the general use of DC has a long way to go.