Guide to 17th Edition Consumer Units

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Significant changes affect installations where cables are
buried in the wall. This is the normal practice in dwellings.
Here we need to consider Section 522, Selection and erection
of wiring systems in relation to external influences. The
particular requirements of this section apply to cables which
are concealed in a wall or partition at a depth of less than
50mm, or where metal partitions are used.
The definitions for persons are once again important for this
section. There are 5 options of installing cables in walls. The
cables shall:
1. Incorporate an earthed metal covering which is suitable
as a protective conductor. Eg SWA cable.
2. Be enclosed in earthed metal conduit, such that is
suitable as a protective conductor.
3. Be enclosed in earthed metal trunking, such that is
suitable as a protective conductor.
4. Be protected against damage
from penetration by nails or
screws.
5. Be installed in a safe zone.
This is much the same as the 16th
Edition requirements and the usual
option is to install cables in a dedicated
safe zone. However, where an installation
is not under the supervision of someone
skilled or instructed, regulation 522.6.7
applies.
In this regulation where (v.) is used then the
cable must have additional protection by the use
of a RCD not exceeding 30mA. This would apply
where thermoplastic (PVC) wiring systems are used,
this is typical in most domestic installations and some
commercial installations.
Cables Buried in the Wall
Guide to | 17th Edition Consumer Units 8