Protecting HVAC equipment is a critical element of electrical distribution system design. Proper selection and coordination of overcurrent protection devices should occur early in the design process, and should address both normal operation and fault conditions.

Occasionally, the calculated fault current exceeds the short-circuit withstand ratings of available starters. Such cases require adding an appropriate current-limiting device or redesigning the electrical system to reduce fault current.

The fault-current analysis in the chiller-motor scenario consisted of a simplified, worst-case calculation. While this is often sufficient to select system components, a number of factors demand more detailed analysis. To learn more, refer to The IEEE Buff Book: Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems published by The Institute of Electrical and Electronics Engineers, Inc.

By Dave Guckelberger, applications engineer, and Brenda Bradley, information designer, Trane.

If you'd like to comment on this article, send a note to Trane, Engineers Newsletter Editor, 3600 Pammel Creek Road, La Crosse, WI 54601. Or, you can e-mail content-related feedback to Dave and general commentary to Brenda.

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