Switch rooms with restricted access space – What intallers need to know

Switch rooms are crucial to the operation and maintenance of electrical equipment in a building but are often of restricted access space, with an an increased risk for injury or accident. Malcolm Doughton considers the additional requirements for such locations.

The control and operation of electrical installations requires the use of switchgear and control gear, and this equipment needs to be both operated and maintained.

It is often located in switch rooms where access is restricted to authorised persons. These locations generally have gangways or passages between the items of equipment, and between items of equipment and building structure.

NOTE:

The additional requirements for operating and maintenance gangways are included in Section 729 of BS 7671:
Requirements for Electrical Installations, as these locations are considered to be areas of increased risk. These additional requirements relate to locations that contain both switchgear and control gear and where the access to the area is restricted to skilled or instructed persons.

Switch rooms often contain exposed live parts and equipment with high current control and switching. The locations are often cramped as architecturally they provide no benefit to the overall space available to the users of the building. Where physical access to a switch room is restricted, this can create a problem when exiting the room. The introduction of additional requirements in BS 7671 Amendment 1 is designed to reduce the risks for personnel working in such locations.

The need for adequate space for access, operation, maintenance, carrying out work and evacuation has long been recognised – for example, they were specified in the Electricity (Factories Act) Special regulations 1908 and 1944. The inclusion of Section 729 has brought recommended minimum distances into the British Standard for the requirements for the electrical installations.

The Electricity at Work Regulations 1989 (EWR) includes requirements for the working space, access and lighting – all of which must be adequate to prevent injury where work is carried out either on or near the electrical equipment. EWR also includes the regulation relating to work on or near live conductors.

The fundamental requirements for accessibility are given in Chapter 13 of BS 7671 – this requires that electrical equipment is arranged to afford sufficient space for the installation and later replacement of electrical equipment. Chapter 13 also requires there to be sufficient accessibility for the operation, inspection, testing, fault-finding and maintenance and repair of the equipment.

The particular requirements of Section 729 consider Basic Protection and other aspects relative to the operation and maintenance of switchgear and control gear within areas, and this includes any gangways.

NOTE:

Access to the locations referred to in Section 729 is restricted to skilled or instructed persons only.
Restricted access areas must:

• Not provide access to unauthorised persons.
• Be clearly and visibly identified by appropriate signs.
• Have doors which allow easy evacuation opening without the use of a key, tool or other device which is not part of the opening mechanism. (This applies where there is restricted access to the location).

In addition, the width of the access areas and gangways must be suitable for the following:

• any maintenance/remedial work to be carried out
• operational access to equipment
• emergency access and evacuation
• transportation of equipment.

Gangways must allow at least 90° opening of any hinged panels or doors forming part of the equipment.

The methods of Basic Protection provided within the location may include barriers, enclosures, obstacles and/or placing out of reach. The minimum dimensions given in Section 729 apply whichever of these methods are used. The basic layout dimensions are as shown in Figure 1.

Where the nature or construction of the equipment requires additional workspace, these dimensions may need to be increased accordingly.

The dimensions shown in Table 1 apply after the barriers, enclosures or obstacles have been fixed in place, and with all the circuit breakers and switch handles in their most onerous position (this includes their
position when they are isolated).

While obstacles and ‘placing out of reach’ are included in the requirements, the Health and Safety Executive (HSE) would not expect any new switchboards to be installed in the UK where there is a potential for access to exposed live busbars.

The minimum requirements for an access-restricted location are shown in Figure 1. The access and positioning of the switchgear and the gangway dimensions would need to be adapted for larger locations.

Within the location, any gangways that are longer than 10m must be accessible from both ends of the gangway.
Where the location exceeds a length of 20m, there must be access doors located at each end of the location (see Figure 2).

It is further recommended that where the location is a closed access-restricted area, access doors at both ends are provided where the maximum gangway length exceeds 6m.

The doors that provide access to the gangways should have a minimum height of 2m, a minimum width of 0.7m and open outwards from the gangways.

While these are recommended minimum dimensions identified in Section 729, there are further requirements given in Annex A to Section 729 that relate to the minimum passing width. The requirements given in Annex A are obligatory and are in addition to those considered thus far.

Annex A further stipulates that gangways must allow the opening of any equipment hinged panels or doors to at least 90°.

To ease the evacuation of the closed restricted-access location, the doors or hinged panels of any equipment within the location must close in the direction of the evacuation route.

There are further additional considerations where the equipment door or hinged panel can be locked in the open position and where circuit breakers can be completely extracted from the panel. in such cases, there must be additional passing width included in the escape route to allow for the fact that these cannot be readily closed by a simple push.

An additional 500mm passing space must be allowed beyond the worst-case scenario – i.e. the maximum open door locked position or maximum extracted circuit breaker position. The additional 500mm is measured to the adjacent obstruction from the equipment whether this is the building structure or other switchgear or equipment (see Figure 3).

While the access to the switchgear and control equipment is restricted to skilled or instructed persons, the location is still considered an area of increased risk. Modern switch rooms and control rooms are being constructed to minimise the risk to those persons operating and maintaining the equipment within the location.

The introduction of the requirements of Section 729 in BS 7671 has provided minimum requirements for these locations, which helps both in the design process and in reducing the risks associated with these locations.

To sum up:

• Operating and maintenance gangway requirements relate to areas that are restricted to skilled and instructed persons.
• Section 729 of BS 7671 identifies the minimum additional requirements for these locations.
• The minimum distances quoted may need to be increased depending on the type of equipment installed.
• Specific requirements are included for the escape routes from within, and to exit, the location.
• Doors and hinged panels of equipment are to be installed to close in the direction of the exit route.
• Where doors and hinged panels can be locked in the open position, an increased escape route width is required.
• Exit doors from the closed location must open outwards and open from within without the use of additional tools or keys other than the fixed opening mechanism.