Unvented Hot Water Storage Vessel Commissioning Record

Approved Document G says an unvented hot water storage system over 15 litres should be installed by a competent person. It gives two examples of showing competence: registration with a competent person scheme, or a current registered operative card for unvented hot water systems (paragraph 3.40). A G3 qualification is the training behind that card.

Yes. Installing an unvented hot water system is notifiable building work (Approved Document G, paragraph 3.41). If you are registered with a competent person scheme for hot water systems, such as APHC, NICEIC or NAPIT, you self-certify and the scheme notifies building control. If not, you notify a building control body, either the local authority or a registered building control approver. A service or inspection is not notifiable.

Approved Document G expects two independent safety devices on top of the thermostat: a non-self-resetting energy cut-out on every heat source and a temperature and pressure relief valve (paragraphs 3.17, 3.18 and 3.33). The system also needs a tundish, discharge pipework to a safe and visible place, an expansion relief valve on the cold supply, and room for expansion, either an expansion vessel or an air space inside the cylinder. CertBox asks about each of these.