HVAC

BuildingWrench repair guide

HVAC

One Room Is Too Humid: Commercial HVAC Troubleshooting

High humidity in one room can come from excess outdoor air, low cooling runtime, exhaust imbalance, moisture sources, sensor error, or airflow problems. Measure temperature and relative humidity before changing setpoints.

Last reviewed 2026-09-12 · General facility-maintenance information, not a substitute for site procedures, manufacturer instructions, codes, or qualified professional judgment.

Routine facility fixSkill: Beginner-friendlyFormat: Diagnose → Fix → Test
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Safety boundary

Do not bypass safeties, open refrigerant circuits, or perform energized electrical diagnosis unless trained and authorized.

Full troubleshooting steps are in Pro

The safety boundary, quick answer and stop-work conditions above stay free. Pro opens the likely causes, symptom table, step-by-step procedure and preventive maintenance for this guide.

Stop and call a licensed professional when

  • Visible mold or persistent wet materials
  • Building-wide humidity is high
  • Controls or air-balance work is needed

Mistakes, FAQ, parts and tools

Pro opens the rest of this guide: common mistakes, field FAQ, the parts list, and the tools for the job.

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Thermostat Says Cooling but Nothing Happens? Commercial HVAC Checks

If the thermostat shows a cooling call but the equipment does nothing, separate the problem into controls, airflow, and equipment response. Verify the schedule and setpoint first, then look for obvious safeties, alarms, airflow restrictions, or a unit that is not responding.

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Water-Source Heat Pump Not Cooling: Facilities Troubleshooting Checklist

For a water-source heat pump that runs but does not cool, verify thermostat demand, airflow, filter condition, loop-water availability, condensate safeties, and whether neighboring units are affected. Refrigerant and internal electrical diagnosis should be escalated.

HVAC

Commercial Thermostat Screen Is Blank: What to Check First

A blank thermostat can mean dead batteries, lost 24-volt control power, a tripped condensate float switch, equipment power loss, or a loose thermostat face.