January 2, 2024 – Electrical contractors have been installing various models of meter bases for residential services, based on what is available at their distributor. But these meter bases may have different neutral assembly configurations from one another; failing to recognize this difference may result in a non-compliant installation and a potential safety hazard.

Neutral assemblies may be installed at the factory, or may be provided as a field-installable kit. There are three kinds:

1. Neutral permanently bonded to the enclosure.
2. Neutral permanently isolated from the enclosure.
3. Neutral supplied with means to bond or isolate from the enclosure, complete with marking on a temporary tag, instruction sheet (or equivalent) indicating how the bond is to be removed or installed.

CE Code-Part I, Rule 10-210, requires the grounding connection of the supply authority system’s grounded conductor (neutral) to be made at one point only at the consumer’s service, and have no other connection to metal parts of the electrical equipment on the supply or load side from where the grounding connection is made.

Where the consumer’s service has a single meter base and service box, the code permits the grounding connection at the meter base or service box, as per Diagrams A and B. The type of meter base used needs to be aligned with the location of the grounding connection. Therefore, it is important to verify the appropriate wiring configuration based on the neutral assembly configuration.

As per Diagram A, when a grounding conductor is connected at a service box, the service neutral conductor has to be isolated from any metal enclosure, including the meter base. A bonding conductor, connected between the meter base and service box, is required per Rule 10-604, and sized per 10-616 (Table 16). Using a meter base with a bonded neutral for this installation would breach CE Code requirements.

Example of marking to indicate the neutral is permanently isolated.

Where the consumer’s service is subdivided in a multi-gang meter base, the grounding connection must be made only at the meter base to achieve “single-point grounding”. It is not permitted at each service box, since each is located on the supply side of the others.

The CSA standard for meter bases (C22.2 No. 115 “Meter-mounting devices”) requires a combination meter base (i.e. meter base with a load-side circuit breaker) to be marked so as to indicate when the meter base is permanently bonded, or has an isolated neutral assembly. All other types are not required to be marked.

In all cases, we want to end up with an installation that is correctly grounded and bonded, compliant and safe.

Nansy Hanna, P.Eng., is senior director, Engineering & Regulations, at Ontario’s Electrical Safety Authority (ESA). She is also chair of the Canadian Advisory Council on Electrical Safety (CACES) and a member of the ULC Advisory Council and CSA Technical Committee on CE Code-Part I. She can be reached at nansy.hanna@electricalsafety.on.ca.

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