Commercial RTU Not Cooling

Likely causes

These categories help organize the diagnostic process; they are not a remote diagnosis.

• Lost power, failed controls, safeties, compressor, fan, motor, or refrigeration component
• Dirty filters or coils, low airflow, duct restriction, economizer fault, or incorrect outside-air condition
• Refrigerant leak, metering problem, excessive load, poor staging, or failing sensors

Safe facility observations

Facility staff may record alarm text, thermostat or BAS display status, affected areas, time of onset, visible water or ice from a safe location, and unusual sound or odor. Do not open energized panels, reset a repeatedly tripping breaker, bypass safeties, force controls, handle refrigerant, work on combustion equipment, or enter pressure systems.

• Record thermostat or BAS command, space temperature, alarm text, and affected zones
• From a safe location, note whether supply airflow, outdoor fans, or unusual sounds are present
• Check only accessible filters and grilles without removing equipment panels

Professional diagnostic process

A qualified diagnosis confirms the call for cooling, power and safeties, control sequence, airflow and static conditions, fans, coils, refrigeration performance, economizer, sensors, load, and connected duct system.

Equipment commonly involved

The fault can originate in the primary equipment or a connected system.

• Packaged rooftop unit
• Thermostat or BAS
• Economizer and dampers
• Supply and return ductwork

Risks of delay

Continued operation can increase tenant impact, humidity, product or process risk, compressor damage, water problems, and energy use.

Repair considerations

Repairs should correct the verified cause and confirm capacity, airflow, drainage, safeties, ventilation, and controls after work.

Replacement considerations

Consider replacement when total condition, repeated failures, refrigerant, parts, controls, curb, ventilation, roof, energy, and downtime outweigh a durable repair.

Related maintenance

Review filters, belts where present, fans, coils, drains, electrical condition, refrigeration indicators, heat, economizer, sensors, safeties, and operating measurements.

Safety notice

This guide is educational and is not a substitute for on-site diagnosis. Follow facility safety procedures and applicable code. If there is smoke, fire, suspected gas, exposed electrical damage, a significant refrigerant release, pressure hazard, or an immediate life-safety concern, evacuate or isolate the area as appropriate and contact emergency or qualified response personnel.