Commercial Chiller Low Pressure Alarm & Flow Switch Triage
Your commercial air-cooled or water-cooled chiller has tripped on a 'Low Evaporator Pressure' or 'No Flow' safety alarm, halting chilled water circulation across the building.
Identifiable Failure Symptoms
- Chiller control panel displays 'Alarm: Low Suction Pressure' or 'Flow Switch Open'
- Chilled water supply temperature rises above 52°F (normal is 42°F-45°F)
- Air handling units (AHUs) across all building floors are blowing warm air
- Water pressure differential across the barrel evaporator drops to zero
Primary Root Mechanical Causes
- Primary chilled water pump failure or tripped VFD (Variable Frequency Drive)
- Clogged inline Y-strainer restricting GPM water flow through the evaporator barrel
- Loss of refrigerant charge due to copper tubing vibration fatigue
- Electronic expansion valve (EXV) closed or stepper motor failure
Initial Safe Verification Steps
Perform these non-invasive safety checks before requesting an on-site technician.
Check Chilled Water Pump Operation
Inspect the mechanical pump room. Is Primary Chilled Water Pump 1 or 2 running? Check pump differential pressure gauges (PSI in vs PSI out).
Inspect Inline Water Strainer Differential
Check the pressure drop across the evaporator barrel inlet and outlet.
Record Chiller Controller Logged Data
Take a photo of the chiller controller diagnostic screen showing: Leaving Chilled Water Temp, Entering Water Temp, Saturated Suction Temp, and Approach Temp.
Safety Protocol — When to Stop DIY
CRITICAL: If a chiller evaporator barrel freezes, water expands inside copper tubes, rupturing the sealed circuit and flooding hundreds of gallons of water directly into the refrigerant circuit. Do not bypass flow switches.
Ascend Professional Repair Protocol
What our licensed technician tests upon dispatch:
- Ultrasonic flow meter measurement of actual GPM flow rate
- Chiller approach temperature analysis and tube fouling calculation
- Electronic expansion valve (EXV) calibration and transducer check
- Oil sample analysis and refrigerant leak testing
North Texas Climate & Equipment Reality
In commercial facilities across Southlake, Irving, and Fort Worth, sudden summer cooling demand spikes push chillers to 100% capacity. Flow restrictions cause barrel temperatures to drop below 32°F rapidly.
Expert Mechanical Insights
Why will my chiller not reset after a low-pressure alarm?
Chiller controllers enforce a hard manual lockout after low-pressure trips to protect the multi-thousand dollar evaporator barrel from freezing solid and bursting internal water tubes.
What is chiller 'Approach Temperature'?
Approach temperature is the difference between the leaving chilled water temperature and the saturated refrigerant temperature. A high approach indicates fouled tubes or poor heat transfer.
Does Ascend service centrifugal, screw, and scroll chillers?
Yes. ASCEND Mechanical Group provides certified commercial mechanical service for Daikin, Trane, Carrier, and York chillers across North Texas.
Related Resolution Blueprints:
Commercial Rooftop Unit (RTU) Not Cooling
Commercial Refrigerant Leak Detection & EPA Compliance
Commercial Mechanical Preventive Maintenance & Failure Prevention
Resolve This Issue Today
Our licensed North Texas mechanical team is on standby with fully stocked trucks for immediate diagnosis and repair.