cu mounting materials

old_guy · Mar 13, 2025

I'm a trainee and about to start doing jobs for my portfolio which includes replacing a CU and I'm wondering if it is still acceptable to install consumer units onto non-combustible material or was it ever acceptable? The relevant regulations appear to be:

131.3.2 Persons, livestock, fixed equipment and fixed materials adjacent to electrical equipment shall be protected against harmful effects of heat or thermal radiation emitted by electrical equipment, and in particular the following: (i) (ii) (iii) Combustion, ignition, or degradation of materials Risk of burns Impairment of the safe function of installed equipment. Electrical equipment shall not present a fire hazard to adjacent materials

421.1.201 Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 and shall: (i) have their enclosure manufactured from non-combustible material, or be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12. NOTE: Ferrous metal, e.g. steel, is deemed to be an example of a non-combustible material.

527.1 .2 A wiring system shall be installed so that the general building structural performance and fire safety are not reduced

421.1.201 and 527.1 .2 are quite specific in that they refer to consumer units/switchgear/wiring however 131.3.2 refers to "fixed materials adjacent to" as I've highlighted in bold so would it be fair to interpret that as meaning the material we mount a cu onto ?

buzzlightyear · Mar 13, 2025

old_guy said:
421.1.201

Is says if you are putting a metel consumer unit in. So I affect it's metel
Fire rated.

Pretty Mouth · Mar 13, 2025

old_guy said:
'm wondering if it is still acceptable to install consumer units onto non-combustible material or was it ever acceptable?

Do you mean combustible, not non-combustible?

old_guy said:
131.3.2 Persons, livestock, fixed equipment and fixed materials adjacent to electrical equipment shall be protected against harmful effects of heat or thermal radiation emitted by electrical equipment, and in particular the following: (i) (ii) (iii) Combustion, ignition, or degradation of materials Risk of bums Impairment of the safe function of installed equipment. Electrical equipment shall not present a fire hazard to adjacent materials

I think this means under non-fault conditions. A CU wouldn't get so hot in normal use to set fire to a timber board that it was mounted on, for example. Interested to hear other members opinions.

old_guy said:
421.1.201 Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 and shall: (i) have their enclosure manufactured from non-combustible material, or be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12. NOTE: Ferrous metal, e.g. steel, is deemed to be an example of a non-combustible material.

old_guy said:
527.1 .2 A wiring system shall be installed so that the general building structural performance and fire safety are not reduced

This means, for example, not compromising the integrity of a fire compartment by fitting non-fire-rated downlights. That sort of thing.

old_guy · Mar 14, 2025

Pretty Mouth said:
Do you mean combustible, not non-combustible?

I think this means under non-fault conditions. A CU wouldn't get so hot in normal use to set fire to a timber board that it was mounted on, for example. Interested to hear other members opinions.

This means, for example, not compromising the integrity of a fire compartment by fitting non-fire-rated downlights. That sort of thing.

Thanks. Yes, I meant combustible.

old_guy · Mar 14, 2025

buzzlightyear said:
Is says if you are putting a metel consumer unit in. So I affect it's metel
Fire rated.

Thanks but I

buzzlightyear said:
Is says if you are putting a metel consumer unit in. So I affect it's metel
Fire rated.

Understood and I get that its common practise to use ply. Being inexperienced as I most definitely am, just wondering why we dont use cement backerboard considering that 131.3.2 does appear to leave things open for debate.