jar546
CBO
The NEC says this under 440.9:
440.9 Grounding and Bonding.
Where equipment is installed outdoors on a roof, an equipment grounding conductor of the wire type shall be installed in outdoor portions of metallic raceway systems that use compression-type fittings.
What it means is this:
Metal raceway systems with compression fittings listed for use in wet locations that are installed on rooftops to supply air-conditioning and refrigeration equipment could be subject to movement and physical damage. This is a result of rooftop activities such as snow removal or roof repair/replacement. These activities can lead to inadvertent separation of the raceway system, compromising the ground-fault return path. The installation of a wire-type equipment grounding conductor provides redundancy of the ground-fault return path to facilitate the operation of the circuit overcurrent protective device (OCPD) in the event of a line-to-ground fault at the air-conditioning or refrigeration equipment.
440.9 Grounding and Bonding.
Where equipment is installed outdoors on a roof, an equipment grounding conductor of the wire type shall be installed in outdoor portions of metallic raceway systems that use compression-type fittings.
What it means is this:
Metal raceway systems with compression fittings listed for use in wet locations that are installed on rooftops to supply air-conditioning and refrigeration equipment could be subject to movement and physical damage. This is a result of rooftop activities such as snow removal or roof repair/replacement. These activities can lead to inadvertent separation of the raceway system, compromising the ground-fault return path. The installation of a wire-type equipment grounding conductor provides redundancy of the ground-fault return path to facilitate the operation of the circuit overcurrent protective device (OCPD) in the event of a line-to-ground fault at the air-conditioning or refrigeration equipment.