In January 2015  BS7671 Amendment 3 was published which part covered consumer units and "like devices".

A pool control panel is extremely like a consumer unit as it has RCD's, MCB's, as well as time switches and contactors

and carries the major part of the house load especially if the pool has electric heating, a sauna or steam unit.  

These new regulations stated that all consumer units and like devices installed must be of metal construction 

or fire proofed with an outer cover or put inside a metal enclosure.  High temperature plastic enclosures were stated as unsuitable. 

There was an extension granted until 30th December 2015 to allow manufacturers of consumer units to produce suitable units.    

Representations were made by the trade about pool plant rooms in outbuildings as far as TT installation and the problems that metal enclosures 

cause and better waterproofing with plastic units.  

A technical publication was produced by the IET in wiring matters.  Copied and points highlighted from Wiring Matters:    

IT IS IMPORTANT TO READ AND UNDERSTAND THIS PUBLICATION

The phrase ‘similar switchgear assemblies’ in Regulation 421.1.201 means those assemblies used for the same fundamental application as a consumer unit.. A consumer unit is defined in Part 2 of BS 7671.

‘Consumer unit may also be known as a consumer control unit or electricity control unit. A particular type of distribution board comprising a type-tested co-ordinated assembly for the control and distribution of electrical energy, principally in domestic premises, incorporating manual means of double-pole isolation on the incoming circuit(s) and an assembly of one or more fuses, circuit-breakers, residual current operated devices or signalling and other devices proven during the type-test of the assembly as suitable for such use.'

An example of a similar switchgear assembly is a three phase distribution board that is intended to be operated by ordinary persons. This would have to have isolation that interrupts the three incoming line conductors and the neutral, rather than just double-pole isolation as mentioned in the above definition.

Regulation 421.1.201 uses the term ‘premises’. The question could therefore arise: 'do the requirements of the regulation apply to a consumer unit or similar switchgear assembly within an outbuilding such as a garages or shed, or mounted on the outside or a building?'

Some dictionary definitions of ‘premises’ are ‘a house or building, together with its land and outbuildings’ and ‘the land and buildings owned by someone’.   However, regulation 421.1.201 was principally introduced to cover the interior of a household building and any garage or other outbuildings integral, attached, or in close proximity to that building.

Doubt could exist about whether or not a particular outbuilding could reasonably be considered to be in ‘close proximity’ to the household building. A way of resolving this might be to make a judgement of the likelihood that fire originating inside the enclosure of a consumer unit or similar switchgear in the outbuilding might lead to the outbreak of fire in the household building or in any outbuilding integral or attached to it. Relevant factors to consider about such an outbuilding might include whether or not that building or its expected contents are highly combustible.

Regulation 421.1.201 is not intended to apply to a consumer unit or similar switchgear assembly that is not within a building, such as a consumer unit mounted outdoors on the outside of a building.   It will have to be metal control systems if installed inside homes.  

We also must not forget that some pool chemicals are oxidising agents and this is covered below underlined.  

It is most Important that you read this with what is covered in the pod cast link as it has been re-published at the same time as this: 

This is quite long - the part that refers to outbuildings is a long way in. 

This requires the designer issues a zero fire spread risk assessment and submit it with the installation test certificate. 

This could cause an insurance problem as the installation designer may not be qualified legally to issue this certificate and this should be considered. 

This is quite long - the part that refers to outbuildings is a long way in. 

This requires the designer issues a zero fire spread risk assessment and submit it with the installation test certificate. 

This could cause an insurance problem as the installation designer may not be qualified legally to issue this certificate and this should be considered.