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Failures of major HVAC systems can be costly and disruptive to address. Much better to find problems early and address them when they’re still small. There are a variety of ways to do that.
First, keep up with maintenance. Although it's easy to put off when budgets are tight, regular maintenance is an excellent way to prevent problems. If scheduled maintenance has to be put off, don't let it go for too long. And be sure to use qualified technicians to perform the work. When they're performing maintenance, skilled technicians may see signs of trouble even in parts of the system they're not working on.
Skilled facility staff can play another important role just by touring the facility on a regular basis. Of course, doing that will let them find major problems, especially in unoccupied spaces. But experienced staff may very well detect signs of trouble that no one else would notice - a funny smell, for example, or an odd noise.
Another good idea is to recommission the system. Also known as retrocommissioning, recommissioning applies commissioning principles to existing systems. The idea is to verify that the system is operating as it was designed to operate.
All these measures have a bonus: Not only will they help prevent problems in the long run, they may very well reduce energy costs by ensuring that HVAC systems are functioning as they were designed to function.