Change Summary

• A sign is now required to be placed at the service-entrance equipment for commercial and industrial installations that indicates the type and location of each on-site optional standby power source. For one- and two-family dwelling units, a sign is required to be placed at the emergency disconnecting means required by 230.85 that indicates the location of each permanently installed on-site optional standby power source disconnect or means to shut down the prime mover as required in 445.18(D).

Expert Analysis

An optional standby system is a system intended to supply power to public or private facilities or property where life safety does not depend on the performance of the system.

For the 2020 NEC, the service disconnecting means for optional standby systems can still be installed at a readily accessible location outside the building or inside nearest the point of entrance. However, an emergency disconnecting means (which could include the service disconnecting means) for a one- or two-family dwelling is now required to be installed and located on the outside of the structure. This required outdoor emergency disconnect can consist of (1) the service disconnect(s), (2) a properly marked meter disconnect(s), or (3) other listed disconnect switches or circuit breakers on the supply side of each service disconnect that are suitable for use as service equipment.

At 702.7(A), new provisions have been instituted to require the on-site optional standby system signage at one- and two-family dwelling units to be placed at the disconnecting means required at 230.85 that indicate the location of each permanently installed on-site optional standby power source disconnect.