Maintaining Your Service Entrance, Part 1

Your service equipment preventive maintenance practices probably include voltage measurements, visual inspections, infrared inspections, and cable testing. But do they include cable limiters?

Cable limiters are passive devices that provide short-circuit fault protection. They are among the few devices you can install on the supply side of the service disconnect [230.82(1)]. Their location here provides a clue as to why you would use them, rather than relying on load-side devices only. It's faster and cheaper to replace a few fuses than to replace several cabinets of switchgear damaged by a short circuit fault.

A perceived downside of using cable limiters is you are adding a device and thus another point of failure. But the intention is for failure to be at that point. Depending on the configuration, the connections to a cable limiter may replace the normal cable terminations and thus not change the total points of failure.

For increased reliability with cable limiters:

• Where practical, use a style that crimps to cables instead of bolting to a cable termination (fewer connections).
• Follow the manufacturer’s installation instructions, using the recommended crimping tool and not something "close."
• Include cable limiters in your thermography program (check connections).
• Conduct resistance tests through cable limiters (again, check connections) during windows of downtime.