Which metric is most closely associated with assessing equipment reliability?

The metric most closely associated with assessing equipment reliability is chiller downtime. This metric directly measures the amount of time that a piece of equipment, such as a chiller, is out of operation due to failures or maintenance issues. High downtime indicates that the equipment is unreliable, as it signifies that the system is frequently needing repairs or is unable to function as intended, therefore impacting overall operational efficiency.

In contrast, other metrics, such as human resource turnover rate, building maintenance cost, and utilization of office space, do not specifically measure the performance or reliability of equipment. While these metrics can provide insights into operational efficiency and resource management, they do not capture equipment performance or the frequency and duration of failures in the same direct way that chiller downtime does. As such, assessing equipment reliability is best accomplished through monitoring downtime, making it the most relevant choice in this context.