Did a trol and found this, not sure whether this has been superceded though;
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Appendix 3 Working space and access; historical comment on revoked legislation (see regulation 15)
Among the legal provisions revoked upon the coming into force of the Electricity at Work Regulations 1989 were the Electricity (Factories Act) Special Regulations 1908 and 1944. Regulation 17 of those Regulations specified minimum width and height dimensions of 'switchboard passage-ways' if there were 'bare conductors' exposed or arranged to be exposed when 'live' so that they may be touched. These related to what are commonly known as 'open type' switchboards which had much exposed copper work, knife switches etc. That regulation (and the key definitions used at that time) are reproduced below for information. The dimensions which were specified by that regulation were arrived at after much consideration of the circumstances at the time. A compromise was struck between the objective of achieving the safety of those who had to work at and operate these 'open type' switchboards and the need to recognise the constraints imposed by the installations existing and the nature of the technology in 1908. Even though the dimensions were a compromise it was widely recognised that they were a good minimum standard which had been found necessary following a number of severe and fatal accidents in factories and power stations due to inadequate space or cluttered access in the vicinity of bare live conductors at these 'open type' switchboards. The dimensions chosen allowed workmen to operate or otherwise work upon the switchboard in reasonable safety and allowed, for example, persons to pass one another in the switchboard passageway without being placed at unacceptable risk of touching live conductors.
Where the need does arise to work on or near live conductors, the principles of providing adequate working space and uncluttered access/egress, which were expressed in regulation 17 of the Electricity (Factories Act) Special Regulations 1908 and 1944, should be given proper consideration.
Regulation 17 (of 1908 Regulations)
At the working platform of every switchboard and in every switchboard passageway, if there be bare conductors exposed or arranged to be exposed when live so that they may be touched, there shall be a clear and unobstructed passage of ample width and height, with a firm and even floor. Adequate means of access, free from danger, shall be provided for every switchboard passage-way.
The following provisions shall apply to all such switchboard working platforms and passage-ways constructed after January 1, 1909 unless the bare conductors, whether overhead or at the sides of the passage-ways, are otherwise adequately protected against danger by divisions or screens or other suitable means:
(a) Those constructed for low pressure and medium pressure switchboards shall have a clear height of not less than 7 ft and a clear width measured from bare conductor of not less than 3 ft.
(b) Those constructed for high pressure and extra high pressure switchboards, other than operating desks or panels working solely at low pressure, shall have a clear height of not less than 8 ft and a clear width measured from bare conductor of not less than 3 ft 6 in.
(c) Bare conductors shall not be exposed on both sides of the switchboard passageway unless either (i) the clear width of the passage is in the case of low pressure and medium pressure not less than 4 ft 6 in and in the case of high pressure and extra high pressure not less than 8 ft in each case measured between bare conductors, or (ii) the conductors on one side are so guarded that they cannot be accidentally touched.
Key definitions used in the 1908 Regulations
Switchboard means the collection of switches or fuses, conductors, and other apparatus in connection therewith, used for the purpose of controlling the current or pressure in any system or part of a system.
Switchboard passage-way means any passage-way or compartment large enough for a person to enter, and used in connection with a switchboard when live.
Low pressure means a pressure in a system normally not exceeding 250 volts where the electrical energy is used.
Medium pressure means a pressure in a system normally above 250 volts, but not exceeding 650 volts, where the electrical energy is used.
High pressure means a pressure in a system normally above 650 volts, but not exceeding 3000 volts, where the electrical energy is used or supplied.
Extra-high pressure means a pressure in a system normally exceeding 3000 volts where the electrical energy is used or supplied.
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Cheers Pete,