Often a scenario will arise in existing installations where a new main or additional metering points are to be installed. In multi-dwelling residences and commercial buildings, new construction and new tenants may need to be added to the existing building load. While the service entrance transformer may have sufficient kVA capacity to accommodate the additional loads, it may not have sufficient provision for additional secondary conductor terminations.
In these cases, a secondary connection cabinet, (or SCC), which houses power bus bars with lug tapping points to fit the system’s power distribution configuration, is used to provide an interface between the utility transformer and the facility’s power main or power meters. SCCs are NEMA rated enclosures, engineered with ample cable bending space and constructed with fully rated busbars and busbar spacing to eliminate safety concerns of field tapping.
Even new service entrance installations can benefit from a secondary connection cabinet, as it will allow for the easy addition of future service points (metered or un-metered). Three situations can create a need to augment a service entrance by cross connection in an SCC to maintain code requirements or to satisfy transformer restrictions:
- When the number of secondary service conductors from the transformer to the metering equipment exceeds the acceptable limit of the transformer. (for example, 12 individual cables)
- When the size of the conductors exceeds the limit for termination in a specified pad-mounted transformer. (for example, 500kcmil copper or 750 kcmil aluminum)
- When the number of service runs per phase required to carry higher voltages exceeds transformer termination limits. (for example, 8 runs per phase)
Using an SCC will effectively satisfy the termination requirements of the power transformer and create additional services or metering points to accommodate the electrical needs of the structure.
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