Hot offices, cold classrooms, and temperature complaints that show up in the work order queue every day are dealt with by facilities teams daily. On the surface, hot/cold calls look like comfort issues and may sound like whining. But in reality, they’re early-warning indicators that something deeper is happening inside your HVAC ecosystem — especially in your air handlers.
Air handlers set the entire foundation for how a building breathes, cools, heats, filters and balances occupant comfort. When something slips, filters clog, sensors fail, or coils get dirty, the first people to notice are the people in the buildings, then it’s the facilities team’s responsibility to diagnose the problem.
Hot/cold calls are simply the symptoms. The HVAC system is often the cause.
“About 30%-40% of the hot/cold calls on medical/surgical floors are a result of equipment failures,” pointed out Andrew Williams, Director of Facility Management, USA Health.
When a hot/cold call comes in, it’s the start of a diagnostic chain
Some basic HVAC concepts:
- Remember to check that outside air dampers are 100%
- Check belts and filters for proper static pressure
- Check the pump’s potential
Temperature complaints usually point to one of a few root issues inside the air handler or its connected system:
- Airflow restrictions: Clogged filters, dirty coils, stuck dampers, or weak belts reduce airflow. Spaces close to the unit may feel too cold. Rooms farthest away warm up and trigger hot calls.
- Faulty temperature control: Sensors that provide inaccurate readings, valves that fail, or reheat coils stuck open or closed destabilize the system. The result: inconsistent zones and unpredictable comfort complaints.
- Zoning and VAV problems: One malfunctioning VAV box can make an entire wing uncomfortable — while the air handler appears to be operating normally.
- Preventive maintenance gaps: Postponed filter changes or skipped inspections slowly erode AHU performance until the system itself becomes at risk of failure. It can be a snowball effect.
- System imbalance: Renovated rooms, new equipment loads, and tenant changes alter airflow needs. Without periodic rebalancing, hot/cold calls become chronic.
Map assets, document knowledge
Miles Corson, HVAC Preventive Maintenance Specialist, HSA Mechanical, noted from his experience:
Undocumented building knowledge can be a huge challenge. I’ve walked into plenty of facilities where one maintenance person knew exactly how everything worked, but very little of that information was actually documented. When that person retires or leaves, a lot of valuable knowledge leaves with them. It can make troubleshooting hot/cold calls much more difficult and turn what should be a quick diagnosis into a much longer process.
Accurate drawings, asset mapping, and system documentation are extremely valuable when trying to diagnose airflow, zoning, or comfort issues. Having that information available helps technicians understand how the building was designed to operate and speeds up troubleshooting significantly. From my side as a Facility Resource, it also helps me perform a more accurate survey and put together better proposals because I have a clearer understanding of the equipment, system layout, and overall facility needs.
The key to diagnosing these symptoms?
Knowing what connects to what.
Documented system relationships — AHU → duct branch → VAV → space — allow technicians to diagnose smarter and faster. ARC Facilities captures that knowledge permanently on mobile devices, so even when experienced staff retire, no one is stuck relying on ceiling tiles and Carl’s memory.
When these are not documented, organizations lose the opportunity to convert hot/cold calls from “annoyances” into operational intelligence.
Connecting it all back to air handler fundamentals
Hot/cold calls are the real-world feedback loop that tells you how well building systems are functioning.
Temperature complaints can be mitigated when:
- Assets are mapped
- Documentation is current
- PMs are up to date
- AHU components are accessible
When those foundations are in place, comfort calls turn into trend data, trend data becomes insight, and insight leads to better decision-making.
The bottom line
Hot/cold calls aren’t interruptions. They’re information.
And when paired with well-maintained HVAC Systems, accurate location mapping, and strong preventive maintenance practices, they become one of the most reliable diagnostic tools a facility leader has.
They tell you where small problems are forming, how your HVAC ecosystem is running, and where your next investment should be.
“To avoid any hot and cold calls, learn each building’s HVAC equipment potential. Every building is not the same,” said Joseph Carpino, Lead Plant Operator, University of Pennsylvania School of Medicine.
Facilities that treat hot/cold calls as intelligence — not noise — operate with fewer unexpected failures, better comfort, and far more predictable budgets.
