Application of BS7671 wiring regulations containerised generating sets


I’m hoping you can settle an argument for me please? We have purchased multiple, fully containerised generators (in 40′ ISO containers) and installed them on sites in the UK. The supplier is denying that it is his responsibility to test the container electrical installation to BS7671:2008 A3 prior to delivery, they are stating that generators are exempt from this. Our argument is that whilst we agree that generators themselves (engine/generator arrangement) are exempt, the container installation with lighting, power, pumps, heaters and fans etc. is not exempt and should be tested to current standards. Can you clarify please?


This question can only be answered by first looking at the applicable laws and regulations and then working down to the case in question. The difference between national laws and contract law may also be important.

1. Laws, Regulations and Standards

First let us review what the law of England requires (Scotland, Wales and Northern Ireland laws etc. are similar): The “top level” document is the Electricity at Work Regulations 1989; working to BS7671 is one way of complying with this, and to the Health and Safety at Work etc. Act, together with all the relevant EU directives etc. as enacted in English law. There may also be duties under the Construction Design and Management Regulations, or other laws etc.

The ultimate onus is on the employer to ensure that his employees are safe under the relevant law.

It is useful at this point to review what the Health and Safety Executive (HSE) says about the status of standards in general

You will see that:

“However, in certain circumstances, and where justified, even fundamental standards [such as this] need not be followed, provided the designer /manufacturer can show compliance with the essential requirements in his technical file by another equally effective method so the level of risk reduction is at least as good as if the standard had been used.”

So, in general, standards do not have to be followed, as long as the objectives are achieved.

Some standards can have legal status:

“Normally the use of standards is voluntary and they do not impose legal responsibilities. However, in some cases legislation may “call-up” a specific standard effectively giving it legal force, or their use by a manufacturer may be declared, effectively binding that person and their product, to the requirements of the standard.”

So, this is where some parts of the wiring regulations become mandatory for domestic premises. Also, if your contract with your customers and / or supplier refers to the wiring regulations, then they have to be adhered to. Let us now look at what the HSE Says about the Electricity at Work Regulations:

Health and Safety Executive – Guidance on Regulations HSR25 – Electricity at Work Regulations 1989:

8. BS 7671 Requirements for Electrical Installations is also known as the IET Wiring Regulations. They are non-statutory regulations which ‘relate principally to the design, selection, erection, inspection and testing of electrical installations, whether permanent or temporary, in and about buildings generally and to agricultural and horticultural premises, construction sites and caravans and their sites’.

9. BS 7671 is a code of practice which is widely recognised and accepted in the UK and compliance with it is likely to achieve compliance with relevant aspects of the Electricity at Work Regulations 1989.

10. There are, however, many types of system, equipment and hazard to which BS 7671 is not applicable; for example, certain installations at mines and quarries, equipment on vehicles, systems for public electricity supply and explosion protection. Furthermore, BS 7671 applies only to installations operating at up to 1000 V ac or 1500 V dc.

From this we read that the supplier has no statutory obligation to ensure that these products comply with BS7671 irrespective of whether they fall under its remit or not.

However, the supplier does, we believe, have to ensure that their equipment is compliant with the Electricity at Work Regulations and one way that suppliers chose to do this is through the BS7671 testing as suggested by the questioner.

By Placing on the Market, we would also expect the equipment to be CE marked which means that it will be compliant with the Machinery Directive (MD) and the Low Voltage Directive (LVD) as well as the Electromagnetic Compatibility (EMC) Directive requirements.