Metal parts of electric equipment associated with a spa or hot tub water circulating system must be bonded together unless they are part of what?

Metal parts of electric equipment associated with a spa or hot tub water circulating system must be bonded together to ensure they do not become energized and pose a shock hazard. However, self-contained spas or hot tubs are designed as complete units with built-in safety features, one of which is that they often incorporate insulation and grounding to prevent electrical hazards. These systems are constructed in such a way that bonding of metal parts is not necessary due to their integrated safety protocols.

In contrast, the other options refer to installations that lack the same degree of inherent safety features, making bonding essential to protect users from potential electrical faults. Regular electrical systems, outdoor installations, and industrial units do not have the same built-in design characteristics that allow them to operate safely without bonding. Therefore, the context of a self-contained spa or hot tub makes it a unique case where bonding is not required, as the overall design effectively mitigates the risks associated with electrical equipment.