5 Common Chiller Problems and How to Diagnose Them

Commercial chillers are complex machines, and when they fail during Oklahoma’s brutal summer heat, the consequences can be severe. This guide helps facility managers and building engineers quickly diagnose common issues and determine the appropriate response.

Quick Problem Reference

Problem	Primary Symptom	Most Common Cause	Urgency
High Condensing Pressure	High head alarm	Dirty coils (air-cooled) or fouled tubes (water-cooled)	Same-day to immediate
Low Evaporator Pressure	Low suction alarm	Restricted water flow or low refrigerant	Immediate if freeze risk
Compressor Short Cycling	Frequent starts/stops	Low charge or oversized unit	Immediate
High Oil Temperature	Oil temp over 180°F	Failed oil cooler or bearing wear	Immediate if over 200°F
Abnormal Noises	Grinding, banging, hissing	Mechanical failure or refrigerant leak	Immediate

Problem 1: High Condensing Pressure

Symptoms

Symptom	What It Indicates
Condenser pressure exceeds design specs	Heat rejection problem
High head pressure alarm	Safety limit approaching
Reduced cooling capacity	Chiller derating itself
Increased compressor amperage	Compressor working harder

Common Causes

Air-Cooled Chillers

Cause	Visual Signs	Fix
Dirty condenser coils	Dust, cottonwood, debris visible	Professional coil cleaning with low-pressure wash
Failed condenser fan	Motor not running or running slowly	Motor replacement or fan repair
Blocked airflow	Obstructions near unit	Clear obstructions, verify clearances

1. Dirty condenser coils (most common)

   • Visual inspection shows dust, cottonwood, or debris
   • Reduced airflow across coils
   • Fix: Professional coil cleaning with coil cleaner and low-pressure wash

2. Failed condenser fan

   • Fan motor not running or running slowly
   • Broken fan blades
   • Fix: Motor replacement or fan repair

Water-Cooled Chillers

Cause	Diagnostic Indicator	Fix
Fouled condenser tubes	High approach temp (over 5°F above design)	Tube cleaning and water treatment program
Cooling tower issues	Low water flow, high CW temp	Inspect tower, check pump, verify treatment
Scaled tubes	Gradual efficiency decline	Chemical cleaning, improve water chemistry

1. Fouled condenser tubes

   • Poor heat transfer due to scale or biological growth
   • High approach temperature (over 5°F above design)
   • Fix: Tube cleaning (brush or chemical) and water treatment program

2. Cooling tower issues

   • Low water flow
   • High condenser water temperature
   • Fix: Inspect tower, check pump, verify water treatment

When to Call for Service

Condition	Response Time
Pressure reaches safety cutout	Immediate—risk of compressor damage
Pressure is 15+ PSI above normal	Within 24 hours
Gradually increasing over weeks	Schedule maintenance (indicates fouling)

Problem 2: Low Evaporator Pressure

Symptoms

Symptom	What It Indicates
Evaporator pressure below design	Heat absorption problem
Low suction pressure alarm	Safety limit approaching
Inadequate cooling output	Chiller capacity reduced
Possible freeze conditions	Tube damage risk

Common Causes

Cause	Diagnosis Method	Fix
Restricted chilled water flow	Check flow meter, verify pump	Clear restriction, repair/replace pump
Low refrigerant charge	Leak detection, check subcooling	Repair leak, recharge (EPA certified)
Fouled evaporator tubes	High approach temperature	Tube cleaning and water treatment

1. Restricted chilled water flow

   • Partially closed valves
   • Clogged strainer
   • Failed pump
   • Diagnosis: Check flow meter, verify pump operation
   • Fix: Clear restriction, repair/replace pump

2. Low refrigerant charge

   • Leak in system
   • Subcooling below specification
   • Diagnosis: Leak detection with refrigerant detector
   • Fix: Repair leak, recharge system (EPA certified technician required)

3. Fouled evaporator tubes

   • Poor heat transfer
   • High approach temperature
   • Fix: Tube cleaning and water treatment

When to Call for Service

Condition	Response Time
Approaching freeze condition (32°F or below)	Immediate
Affecting critical cooling loads	Same day
Preventative tube cleaning needed	Scheduled

Problem 3: Compressor Short Cycling

Symptoms

Symptom	Impact
Compressor starts and stops every 2-5 minutes	High mechanical stress
Never reaches stable operation	Reduced efficiency
High inrush current on each start	Electrical system stress
Mechanical stress on components	Accelerated wear

Common Causes

Cause	How to Identify	Fix
Low refrigerant charge	Running on low-pressure cutout	Locate leak, repair, recharge
Oversized chiller for load	Common in shoulder seasons	Install capacity control or staging
Failed control sensor	Erratic temp/pressure readings	Sensor calibration or replacement
Electrical issues	Loose connections, failed contactor	Electrical diagnostics and repair

Impact on Equipment Life

Short cycling dramatically reduces equipment life. A compressor designed for 3-5 starts per hour being subjected to 20+ starts can fail within months instead of years.

When to Call for Service

Condition	Response Time
Any short cycling condition	Immediate—causes rapid component wear
Affecting hospital, data center, or process cooling	Critical

Problem 4: High Oil Temperature (Centrifugal Chillers)

Symptoms

Symptom	Risk Level
Oil temperature exceeds 180°F	Warning
High oil temperature alarm	High
Bearing wear concerns	Critical
Potential lubrication failure	Critical

Common Causes

Cause	Diagnostic Method	Fix
Failed oil cooler	Check approach temperature	Clean or replace oil cooler
Low oil level	Check sight glass	Add oil, repair leak
Bearing wear	Oil analysis, vibration testing	Bearing replacement (major service)

1. Failed oil cooler

   • Fouled tubes
   • Low coolant flow
   • Diagnosis: Check approach temperature
   • Fix: Clean or replace oil cooler

2. Low oil level

   • Oil leak
   • Failed oil pump
   • Diagnosis: Check sight glass
   • Fix: Add oil, repair leak

3. Bearing wear

   • Increased friction generates heat
   • Vibration may be present
   • Diagnosis: Oil analysis, vibration testing
   • Fix: Bearing replacement (major service)

When to Call for Service

Condition	Response Time
Oil temp exceeds 200°F	Immediate shutdown—bearing damage risk
Approaching alarm setpoint	Same day
Routine oil analysis on critical units	Quarterly

Problem 5: Abnormal Noises

Diagnosis by Sound

Sound Type	Likely Cause	Action
Grinding or screeching	Bearing failure, dry bearing, shaft misalignment	Immediate shutdown to prevent catastrophic damage
Banging or hammering	Liquid refrigerant in compressor (liquid slugging)	Check superheat, verify expansion valve
Hissing	Refrigerant leak, safety valve lifting	Evacuate area, call for emergency service
Clicking or chattering	Loose mounting bolts, relay issues, loose panels	Inspect and tighten, verify electrical components

Grinding or Screeching

• Cause: Bearing failure, dry bearing, shaft misalignment
• Action: Immediate shutdown to prevent catastrophic damage

Banging or Hammering

• Cause: Liquid refrigerant in compressor (liquid slugging)
• Action: Check superheat, verify expansion valve operation

Hissing

• Cause: Refrigerant leak, safety valve lifting
• Action: Evacuate area, call for emergency service

Clicking or Chattering

• Cause: Loose mounting bolts, relay issues, loose panels
• Action: Inspect and tighten, verify electrical components

Emergency Decision Matrix

Condition	Response Time	Risk Level
Safety alarm (high pressure, high temp)	Immediate shutdown	Critical
Lost cooling in hospital OR	Emergency dispatch (under 2 hrs)	Critical
Refrigerant leak	Same day	High
Reduced capacity in summer	Within 24-48 hours	Moderate
Gradual efficiency loss	Schedule maintenance	Low

Preventative Measures

Most chiller failures are preventable with proper maintenance:

Preventative Action	Frequency	What It Catches
Quarterly inspections	Every 3 months	Developing issues before failure
Annual tube cleaning	Yearly	Fouling and scale buildup
Water treatment programs	Continuous	Scale and corrosion prevention
Oil analysis (centrifugal)	Quarterly	Bearing wear early detection
Vibration monitoring	Monthly or continuous	Mechanical problems before failure

Need Expert Help?

Total Mechanical Services provides 24/7 emergency chiller service across Oklahoma. Our factory-trained technicians service all major brands:

Brand	Equipment Types
Trane	Centrifugal, screw, air-cooled
York	Centrifugal, screw, air-cooled
Carrier	Centrifugal, screw, air-cooled
Daikin	Centrifugal, screw, air-cooled
McQuay	Centrifugal, screw, air-cooled

Emergency Hotline: (405) 223-9900

Request a Service Quote

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This troubleshooting guide is for informational purposes. Refrigerant handling requires EPA 608 certification. High-voltage electrical work should only be performed by qualified technicians.