ANSI C12.7-2022: Watthour Meter Sockets

Watthour electric meter measurement tool located outside the home adhering to ANSI C12.7-2022.

A meter socket is a critical component in any home’s electrical system. It connects your property to the utility grid, ensuring accurate energy consumption tracking. This junction point is essential for power management and safety. ANSI C12.7-2022: Requirements For Watthour Meter Sockets applies to watthour meter sockets and its components.

What Is ANSI C12.7?

ANSI C12.7-2022 covers the general requirements and pertinent dimensions applicable to watthour meter sockets. It defines a meter socket (socket) as “an enclosure that has matching jaws to accommodate the bayonet-type (blade) terminals of a detachable watthour meter and has a means of connection for the termination of the circuit conductors. It may be a single-position socket for one meter or a multi-position socket for two or more meters.”

The sockets in the scope of this American National Standard are rated up to and including 600 V and up to and including 320 A continuous duty per socket opening. This standard specifies the electrical ratings, performance and construction requirements, and test blocks for meter sockets.

What Is a Watthour Meter?

Power purchased from a utility company enters the house through a watthour meter, also referred to as a socket meter. Watt-hour meters used in most residential applications are designed for use with single-phase power. Residential applications often use a watt-hour meter designated as self-contained (SC). SC meters are directly connected to the power source and the load.

Meters used in many commercial applications are designed for use with three-phase power. Watt-hour meters designated as transformer rated (TR) use current transformers (CTs) and voltage transformers (also called potential transformers or PTs) to reduce the energy applied to the meter. TR meters are common in commercial applications due to the higher load current required for these applications.

Each watt-hour meter requires a meter socket to safely and securely connect it to the electrical service.

What Is a Meter Socket?

A meter socket is a type of outdoors electrical socket that connects a watt-hour meter, or electrical meter, to a property. A basic meter socket has five components: enclosure, lugs, neutral connections, jaws, and insulating blocks. This meter is seen outside houses, commercial buildings, and construction sites. It is durable and weatherproof, allowing it to stand up to rain, wind, snow, and other elements of nature.

The main difference between various meter sockets is the amount of amps they can safely read. They generally range from 100 amps to 320 amps. Light meter sockets are able to handle about 100 amps, which is usually enough power for small houses; whereas, bigger properties or construction sites are able to handle around 320 amps or more. If a meter socket has a lower amp rating than the amount of amps being used, the socket will typically short out or run into problems when attempting to measure the amount of energy being used.

Moreover, the role of a meter socket is to accurately measure the amount of power used, so a utility company knows what to charge for billing purposes. It provides a safe and standardized interface for utility companies to connect and disconnect the power supply to a property, allowing efficient meter reading and maintenance.

What Is the Difference Between a Meter Socket and a Meter Main?

From the watt-hour meter, the incoming power then goes to a load center which provides circuit control and overcurrent protection. The power is distributed from the load center to various branch circuits for lighting, appliances, and electrical outlets. Typically, the load center enclosure is separate from the meter socket. In some cases, however, circuit breakers are housed in the same enclosure as the meter socket. This type of product is referred to as a meter combo. When only a main circuit breaker is included, the device is called a meter main.

ANSI C12.7-2022: Requirements For Watthour Meter Sockets is available on the ANSI Webstore.

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