Well connected?

Junction boxes are an integral part of virtually every electrical installation. They generally supply the connection between fixed wiring and downlights, with the lighting circuit looped between fittings.

Unfortunately, these connections often do not comply with either the 16th Edition or the new 17th Edition of the Wiring Regulations. Part of the problem is a lack of suitable products available to meet the realities of the actual installation. There are several issues that need addressing.

First, as highlighted by the Electrical Safety Council’s Technical Manual, all electrical connections must be accessible for inspection testing and maintenance. There are certain exceptions, but both the 16th and 17th editions are clear.

“Junction boxes with screw terminals must be accessible for inspection, testing and maintenance, or alternatively use maintenance-free terminal connections.”

The Electrical Safety Council says such connections should be located where they can be reached and where there is adequate working space.

The Technical Manual says: “Where connections are made in roof spaces, inter-floor spaces and other non-readily-accessible locations… provision must be made for access by providing, for example, removeable access traps in the ceiling.”

It goes on to state: “A fitted carpet can effectively render connections beneath a floor inaccessible because of objections from the building owner to the carpet being lifted or difficulties in finding the access trap.

“Generally, therefore, connections required by Regulation 526-04-01 to be accessible should not be located under a floor where a fitted carpet is likely to be laid.”

Unfortunately, in many homes and offices this could apply to most rooms.

Often the junction box is reached via the hole in the ceiling behind the ceiling rose. Pulling a conventional junction box through the hole can damage the terminal connections.

Which brings us to regulation 522-08-05. This requires that every cable or conductor used as fixed wiring must be supported in such a way that there is no appreciable mechanical strain on the terminations of the conductors.

Often this means that junction boxes are fixed to a suitable firm surface. This is fine, but it can lead to accessibility problems if its only practical access is through the ceiling hole.

Also, this would not necessarily relieve the strain from the weight of cables or fittings from the downlighter.

An alternative is to securely clamp the cables as they enter or exit the junction box, a feature that is too often absent from many designs.

The Health and Safety Executive makes the same point in a document Cable joints and repairs. Section 4 subsection (iii) reads:

“Junction boxes often provide mechanical protection but frequently do not give any stress relief to the conductors. Junction boxes are not generally suitable for use with flexible cables unless special cable glands are used.”

Clamping the cables securely would also overcome another problem: it would eliminate exposed unsheathed conductors. Regulation 526.9 from the 17th Edition states: “Cores of sheathed cables from which the sheath has been removed… shall be enclosed, as required by Regulation 526.5.”

The 16th Edition makes the same point.

Terminating different-sized connectors in the same terminal is another potential problem.

This is also covered by the 17th Edition: “Electrical connections should provide durable electrical continuity, and be suitable for the conductor csa [cross-sectional area], shape and the number of conductor strands.”

Most junction boxes currently use the same terminals for both the twin and CPC cables, plus the flexible cable feeding the light fitting. These flexible cables generally have conductors that consist of a relatively large number of thin strands, while fixed wiring normally has conductors that are either solid or have few thick strands.

Terminating these different conductors in the same block can cause damage to smaller flexible conductors or result in an insecure connection.

A loose or disconnected cable is a hidden danger with junction boxes. With Part P and an increasing drive for safety, these products have come under close inspection. Potentially the contractor has a problem since many lighting circuits may fail the Wiring Regulations. This needs to be addressed.