Certification and Sealing
All domestic meters used for billing purposes by a licensed electricity supplier must be certified to show that, when tested following manufacture/refurbishment, they conformed to the original pattern approval and operated within the prescribed levels of accuracy. They may then be used for a specified period of time after which they must be removed from circuit.
This process is described in detail in The Meters (Certification) Regulations 1998, SI 1566 (as amended). This prescribes that all meters, following approval, be allocated a certification life (i.e. the time a meter is allowed to remain on circuit from initial certification). Meters for industrial and commercial customers are either certified or the supplier reaches agreement with the customer for a meter with a similar level of accuracy to be fitted. Certification life is allocated by NMO/Ofgem and is restricted to 10 years for newly approved induction meters and for periods of between 10 and 20 years for static meters. Certification periods greater than 10 years (for electronic meters) are subject to the submission and validation of a component reliability model based on the Siemens Norm SN29500. Subsequent in-service surveillance monitoring can result in either increase or decrease of this period.
Prior to submission for certification meters will have a uniquely marked seal attached. In the UK meters can only be certified by a meter examiner appointed under the regulations.
Meters need not be certified where the supplier does not hold a supply license. This provides for situations where the supplier might be a landlord selling on electricity to tenants, or a caravan park owner billing individual berth occupiers. However an agreement must be in place between the two parties and the meter owner is obliged to use an approved meter and keep the meter in good working order.
All certified meters are sealed. A seal is used to provide security for the measuring elements of a meter from tamper, identify the manufacturer/repairer of the meter, the year of certification and the fact that the meter is certified. The seal can take the form of a crimped security seal on traditional meters or an indelible inscription on the meter case for sealed for life static meters.