Guidance on your responsibility when erecting or installing equipment.
Anyone who installs or erects equipment as part of a work activity must do so properly, following the manufacturer's instructions, so that nothing about the way it has been done makes it unsafe or gives rise to a health risk. You have this responsibility when installing or erecting equipment for use at work (eg installing machinery in an office or factory), and also when providing a service to non-employed persons as part of a work activity (eg installing a powered gate on domestic premises).
In some cases, installers may have additional responsibilities when they effectively become the manufacturer of a new product. For example, if you install a power mechanism on an existing manually-operated gate, you - as installer - will now also effectively be the manufacturer of a 'new' machine and so have to meet all of the manufacturer's obligations under supply law.
If, when following the manufacturer's instructions for installing or erecting equipment, you consider that the product will be unsafe when finally brought into use, you should report your concerns to both the manufacturer and the new user. If necessary, do so in writing so they are fully aware of the health and / or safety issues. In some cases you may be obliged not to connect (or to disconnect) the equipment so that users are not placed at risk (eg installers of gas appliances). You can also report your concerns about design and construction defects to the relevant market surveillance authority as they may have statutory powers to take action over the matter.
All employers and the relevant self-employed are obliged to conduct their work in such a way, as far as reasonably practicable, that does not expose other people - whether other workers or members of the public - to risks to their health or safety (see section 3 of the Health and Safety at Work etc Act 1974). This obligation is further defined, under section 6(3) of the Act, to include any work erecting or installing equipment. If you are self-employed and your work poses no risk to the health and safety of others, then health and safety law may not apply to you. HSE has guidance to help you understand if the law applies
Whether installers also become in effect manufacturers - and so dutyholders, for example under the Supply of Machinery (Safety) Regulations 2008 when installing powering equipment to existing manual gates - will depend on the circumstances of each individual contract. Normally the person putting a new product into service takes on the duty for compliance, including undertaking conformity assessment to meet the essential requirements and CE marking. However, this may be dictated by who exercises primary control for the installation activity. The responsibilities of sub-contractors working under the direct control of others may be limited to their own actions, with conformity assessment and CE marking being the responsibility of the main contractor.