A chiller that runs 20% below its design efficiency costs more to operate every single day than the annual service contract that would have prevented the degradation. Yet most chiller failures — compressor trips, refrigerant leaks, condenser tube fouling, oil system contamination — develop over weeks before they become emergencies, and every one of them produces measurable warning signs that structured PM inspection captures before failure. This checklist covers every chiller type — centrifugal, screw, and scroll — across every PM frequency from daily parameter logging to annual oil analysis and pressure testing, with the acceptance criteria and measurement standards that turn a service visit into a defensible maintenance record. Book a demo to see OxMaint's chiller PM module with automated scheduling, operating log trending, and condition-based alert configured for your chiller plant.
20%
average efficiency loss in chillers running without structured PM — costing thousands monthly before any visible failure
$85K
average cost of a centrifugal compressor rebuild that structured oil analysis and operating log trending typically prevents
6
PM phases covered — daily monitoring, monthly, quarterly, annual, centrifugal-specific, and screw/scroll-specific
85+
individual inspection items with acceptance criteria, measurement fields, and sign-off requirements across all chiller types
How to Use This Checklist
1Complete Phases 1 through 4 for all chiller types on the stated frequency. Add Phase 5 for centrifugal chillers or Phase 6 for screw and scroll chillers as applicable to your equipment.
2Record actual measured values at every item that includes a measurement field — operating log data is only useful if trended across multiple PM cycles, not collected once and filed.
3Photograph all findings rated Action or Critical before any corrective work begins — pre-correction photos are essential for warranty claims, insurance documentation, and contractor accountability.
4Record chiller model, serial number, refrigerant type, nominal tonnage, and runtime hours as header data before starting any phase.
Priority Classification
Critical Immediate action — do not defer; continued operation risks compressor damage or refrigerant release
Action Schedule corrective work within current service window before next PM cycle
Monitor Log condition, increase measurement frequency, escalate if trend worsens
Pass Within acceptable parameters — continue current PM programme
Phase 1
Daily and Weekly Operating Log
Daily & Weekly
All Chiller Types
Operating Parameters
1.1 Daily Operating Parameter Log
Record chilled water supply and return temperatures — design delta-T is typically 10°F; a narrowing delta-T (below 8°F) indicates low flow, fouled evaporator, or a load below minimum — a widening delta-T (above 12°F) indicates high load or low refrigerant charge. CHWS: ______°F CHWR: ______°FAction
Record condenser water supply and return temperatures (water-cooled) or entering and leaving air dry-bulb temperature (air-cooled) — condenser approach temperature above design indicates fouling or low water flow. CWS: ______°F CWR: ______°FMonitor
Record refrigerant suction and discharge pressures and convert to saturated temperatures — compare evaporating temperature to chilled water leaving temperature; approach above 3°F indicates evaporator fouling. Suction: ______psig Discharge: ______psigAction
Record compressor motor running amps on all phases and compare to nameplate FLA — amps more than 10% above FLA at current load conditions require immediate investigation; unbalanced phase current above 2% indicates electrical issue. L1: ______A L2: ______A L3: ______ACritical
Record chiller kW input and calculate kW/ton at current load — kW/ton trending above nameplate design by more than 10% at equivalent load conditions indicates degradation requiring investigation. kW: ______ Tons: ______ kW/ton: ______Monitor
1.2 Weekly Visual and Safety Check
Inspect chiller exterior for oil staining at refrigerant connections, service valves, and brazed joints — oil migration is the primary visible indicator of refrigerant leak; any oil staining requires electronic leak testing at that locationCritical
Check oil level in sight glass (reciprocating and screw chillers) — oil level below the minimum sight glass mark during operation indicates oil loss to refrigerant circuit requiring immediate investigation. Oil level: ______Critical
Review chiller control panel fault log — record all fault codes that occurred since last log review, investigate any repeat faults that have occurred more than twice in 30 days, and escalate to service contractor if fault pattern is not identifiedAction
Verify chilled water and condenser water pump operation — check differential pressure across each pump and compare to design curve; pump differential below design by more than 15% indicates impeller wear or flow restriction. CHW pump dP: ______psid CW pump dP: ______psidMonitor
Phase 2
Monthly Inspection
Monthly
All Chiller Types
Refrigerant · Electrical · Controls
2.1 Refrigerant System Checks
Perform electronic refrigerant leak test at all high-risk locations: compressor shaft seal, service valve packing, brazed or flared connections, and evaporator and condenser tube sheets — federal regulations require leak testing at defined intervals for systems above 50 lbs refrigerant charge. Leaks found: Y / NCritical
Check refrigerant charge using superheat and subcooling method at current operating conditions — superheat below 5°F risks liquid slugging to compressor; subcooling below 10°F indicates undercharge. Superheat: ______°F Subcooling: ______°FCritical
Inspect refrigerant moisture indicator sight glass — moisture indicator colour should be in the dry zone (green or clear on most indicators); yellow or wet indication requires immediate refrigerant drying before acid formation damages compressorCritical
Verify expansion valve or electronic expansion valve operation — stable superheat at varying load conditions confirms EEV is controlling correctly; hunting superheat (oscillating more than 5°F) indicates EEV or sensor issue. EEV stability: ______Action
2.2 Electrical and Control System Checks
Inspect starter or VFD enclosure — confirm cooling fan is operational, filter is clean, and no discolouration or burn marks are visible on terminals or bus bars; discolouration indicates overheating from loose connections or overloadAction
Test low-pressure and high-pressure safety cutout operation — verify cutout pressures match manufacturer settings in the control panel; safety devices that have drifted from set point provide inadequate protection and are a liability risk. LP setpoint: ______psig HP setpoint: ______psigCritical
Verify chilled water setpoint and reset schedule in chiller controller — confirm occupied and unoccupied setpoints are correct; an incorrect setpoint that over-cools during unoccupied hours increases chiller energy consumption by 8 to 15%Monitor
Calibrate chilled water leaving temperature sensor against a calibrated reference thermometer — a CHWS sensor reading 2°F out of calibration causes the chiller to over-cool or under-cool continuously without fault codes. Sensor reading: ______°F Reference: ______°FAction
Phase 3
Quarterly Service Inspection
Quarterly
All Chiller Types
Tubes · Condenser · Water Circuit
3.1 Heat Exchanger and Tube Inspection
Calculate evaporator approach temperature at full load — saturated evaporating temperature (from suction pressure) minus chilled water leaving temperature; above 3°F approach indicates tube fouling that reduces chiller capacity and efficiency. Approach: ______°FAction
Calculate condenser approach temperature at full load (water-cooled) — condenser water leaving temperature minus saturated condensing temperature (from discharge pressure); approach above 3°F indicates condenser tube fouling or low water flow. Approach: ______°FAction
Mechanically brush condenser tubes when approach temperature exceeds 3°F above clean baseline — do not defer tube brushing when approach data indicates fouling; each 1°F of additional condenser approach adds approximately 1.5% to chiller energy consumptionAction
Inspect air-cooled condenser coil fins for fouling, bent fins, and debris — clean with low-pressure water flush from inside out; measure entering and leaving air temperatures to calculate condenser approach and compare to design. Coil condition: ______Action
3.2 Chilled and Condenser Water Circuit Checks
Test chilled water chemistry — pH (target 8.0 to 9.5 for closed loop), inhibitor concentration, hardness, and biological activity; closed loop chemistry outside specification causes corrosion and deposit formation that shortens evaporator tube life. pH: ______ Inhibitor: ______Action
Inspect and clean strainer screens on chilled water and condenser water circuits — partially blocked strainers reduce pump differential and chiller flow; verify differential pressure across each strainer is within acceptable range. CHW strainer dP: ______psid CW strainer dP: ______psidMonitor
Verify chilled water and condenser water flow rates using pump differential pressure and pump curve — chilled water flow below design by more than 15% causes evaporator freezing risk and reduced chiller capacity. CHW flow: ______ GPM Design: ______ GPMCritical
Inspect flexible connections, pipe insulation, and visible valve positions in the chiller plant — confirm all isolating valves are in correct operating position; a partially closed chilled water isolation valve is one of the most common causes of unexplained chiller performance lossMonitor
Phase 4
Annual Comprehensive Service Most Thorough
Annual
All Chiller Types
Oil Analysis · Leak Test · Full Inspection
4.1 Oil Analysis and Lubrication System
Collect oil sample for laboratory analysis — oil analysis should test for viscosity, acid number, moisture content, particulate contamination, and wear metals (iron, copper, aluminium); elevated copper above 50 ppm indicates bearing or valve wear; moisture above 100 ppm requires oil change. Sample date: _______ Lab results: attached Y / NCritical
Change oil filter(s) regardless of current condition — annual oil filter replacement is mandatory; inspect removed filter element for metallic particles indicating internal wear that oil analysis may have flagged; photograph heavily contaminated filters. Filter condition: ______Action
Verify oil heater operation during off-cycle — confirm oil heater maintains oil sump temperature above dew point to prevent refrigerant migration into oil during standby; oil heater failure leads to liquid slugging on start-up that causes compressor valve damage. Oil heater: Operational Y / NCritical
Check oil pressure differential across oil filter at operating temperature — differential above 10 psid indicates filter restriction requiring immediate filter change; below 3 psid at operating speed indicates oil pump or pressure regulating valve issue. Oil filter dP: ______psidAction
4.2 Full Refrigerant System and Pressure Test
Perform comprehensive refrigerant leak test of entire system with calibrated electronic detector at all joints, connections, valve stems, and shaft seals — document all test points inspected; EPA Section 608 requires annual inspection for systems with more than 50 lbs refrigerant charge. Leak rate: ______% annuallyCritical
Verify refrigerant charge by measuring subcooling and superheat at full load against manufacturer specification — record refrigerant charge log entry in the equipment history; document any refrigerant added with quantity and certification number of the technician performing the workAction
Test and certify high-pressure relief valve and rupture disc (large centrifugal chillers) — confirm relief valve is not corroded or weeping; check rupture disc for deformation; verify relief line terminates correctly per ASHRAE 15 requirements. Relief valve condition: ______Critical
4.3 Electrical and Mechanical Annual Checks
Perform infrared thermography on motor starter or VFD panel, main disconnect, and chiller control panel — any connection point showing more than 20°C rise above ambient indicates resistance heating from loose or corroded connection requiring immediate repair. IR scan date: _______Action
Test motor insulation resistance with megohmmeter — record insulation resistance and polarisation index; insulation resistance below 1 megohm or PI below 1.5 indicates motor insulation degradation requiring manufacturer assessment before continued operation. Insulation resistance: ______MΩCritical
Inspect vibration isolators, spring isolators, and flexible connections for deterioration — measure and record vibration levels at compressor, motor, and pump bearings; vibration above 0.3 in/sec RMS at bearing housings requires investigation. Compressor vibration: ______ in/secMonitor
Generate annual chiller performance report comparing measured kW/ton against design efficiency at comparable load conditions — store report in equipment asset record and use to define scope for next annual service; file in CMMS against chiller equipment recordMonitor
Phase 5
Centrifugal Chiller Specific Checks
Quarterly & Annual
Centrifugal Only
Impeller · Gearbox · Vanes · Purge
5.1 Compressor and Drive Train
Monitor pre-rotation vane or inlet guide vane position and modulation — verify vane actuator stroke is full range and vanes respond correctly to load changes; stuck or limited-range vanes prevent capacity modulation and cause surge at low load. Vane range: ______ to ______ %Action
Monitor for compressor surge during low load operation — surge presents as a rhythmic banging or whooshing sound and causes vibration spikes; chronic surge causes impeller and diffuser erosion and vane fatigue; check anti-surge settings in controller. Surge events in log: ______Critical
Inspect gearbox oil level and verify oil pressure at operating speed (open-drive and geared centrifugal) — gearbox oil pressure below the minimum setting is a trip condition; verify the low-oil-pressure safety trip test has been completed at the current annual serviceCritical
Inspect shaft seal for leakage on open-drive centrifugal chillers — any refrigerant or oil weeping from the shaft seal area indicates seal degradation; shaft seal replacement is scheduled maintenance on most open-drive centrifugal chillers at 25,000 to 40,000 runtime hoursAction
5.2 Purge Unit (Low-Pressure Centrifugal Chillers)
Review purge unit log for purge rate — purge rate above 2 lbs of refrigerant per 24 hours indicates excessive air and moisture infiltration through a leak in the low-pressure system that requires immediate leak detection and repair. Purge rate: ______ lbs/24hrCritical
Inspect purge unit carbon filter and replace if saturated — a saturated carbon filter releases captured refrigerant to atmosphere rather than returning it to the chiller, increasing refrigerant losses and operating cost; replace carbon filter annually regardless of saturation levelAction
Verify purge unit compressor operation and refrigerant charge — a purge unit that is not operating correctly allows air and moisture to accumulate in the main chiller which reduces heat transfer efficiency and accelerates internal corrosionAction
Phase 6
Screw and Scroll Chiller Specific Checks
Quarterly & Annual
Screw & Scroll
Slide Valve · Rotor · Capacity Steps
6.1 Screw Compressor Specific Checks
Verify slide valve modulation response across the full capacity range — slow slide valve response or limited travel indicates hydraulic or mechanical slide valve issue that limits chiller capacity modulation and causes cycling at part load. Slide valve range: ______ to ______ %Action
Monitor discharge gas temperature — discharge temperature above 220°F on a screw compressor indicates inadequate oil injection cooling, high compression ratio from low suction pressure, or low refrigerant charge; sustained high discharge temperature accelerates bearing wear. Discharge temp: ______°FCritical
Verify oil separator efficiency — measure oil carryover in refrigerant circuit by checking sight glass clarity; excessive oil in the refrigerant circuit coats evaporator and condenser tubes with an insulating film that significantly reduces heat transfer. Oil carryover visible: Y / NAction
Record rotor running clearances (if accessible during major service) and compare to OEM specification — worn rotor tip clearances reduce volumetric efficiency and increase slip, manifesting as rising kW/ton at equivalent load conditions before any other symptom appearsMonitor
6.2 Scroll Compressor Specific Checks
Verify correct rotation direction for all scroll compressors — reverse rotation destroys scroll compressor internal components within minutes; check rotation on any compressor that has had electrical work on its circuit since last service. Rotation correct: Y / NCritical
Inspect capacitor condition on PSC-motor scroll compressors — swollen, leaking, or deformed capacitors indicate imminent failure; capacitor failure causes scroll compressor to draw excessive current and trip on overload protection before mechanical failure occurs. Capacitor condition: ______Action
Verify crankcase heater operation on all scroll compressors — crankcase heater failure leads to refrigerant migration into the oil sump during standby and liquid slugging on start-up; check heater current draw to confirm heater is energised and functional. Heater current: ______ACritical
On multi-compressor scroll chillers, verify load staging sequence — confirm compressors cycle on and off in the correct rotation order to equalise runtime hours; unequal staging causes premature wear on lead compressors and emergency availability risk. Runtime hours per compressor: logged Y / NMonitor
Inspection Sign-Off and Header Record
Technician Name
Inspection Date
Chiller Model / Serial
Refrigerant Type
Nominal Tonnage
Supervisor Sign-Off
Critical Findings Summary
PM Status Determination
OxMaint's chiller PM module digitises this entire checklist — operating log trend analysis, oil analysis scheduling, refrigerant leak log compliance tracking, and automatic corrective work order generation for every flagged finding. All records linked to the chiller asset history for trending and warranty documentation. Book a demo to see the chiller PM module configured for your plant.
How OxMaint Digitalises This Chiller PM Checklist
A paper chiller PM log produces a point-in-time snapshot that cannot be trended, compared across campaigns, or used to predict failures. OxMaint transforms every operating log reading, oil analysis result, and inspection finding into a structured digital record linked to the specific chiller asset — enabling kW/ton trend analysis, approach temperature deterioration tracking, and oil wear metal monitoring over time.
Operating Log Trending
Daily operating log readings entered on mobile are automatically plotted on trend charts per chiller asset — kW/ton, approach temperatures, refrigerant pressures, and motor amps trended over time to surface deteriorating equipment weeks before failure.
Oil Analysis Scheduling
Annual oil sample collection tasks auto-generated per chiller with laboratory submission tracking, result upload to the asset record, and automatic alert when oil analysis results indicate wear metals, moisture, or acid above action thresholds.
Refrigerant Leak Log Compliance
EPA Section 608 compliance documentation maintained automatically — refrigerant additions logged with technician certification numbers, annual leak inspection records archived, and leak rate calculations generated from the refrigerant charge history per chiller.
Automated PM Scheduling
All phases of this checklist auto-generated on correct frequencies per chiller asset. Daily log tasks, monthly inspections, quarterly service, and annual comprehensive service created and assigned automatically — with escalation if tasks are not completed on schedule.
Automatic Work Order Generation
Any PM finding rated Action or Critical generates a linked corrective maintenance work order pre-populated with the finding, equipment details, and photos — assigned to the responsible technician with a target date before the next PM cycle.
Annual Performance Reports
Chiller seasonal performance reports comparing measured kW/ton to design efficiency generated automatically from operating log data — formatted for energy audits, warranty submissions, and capital planning discussions with building ownership.
Turn Paper Chiller Logs Into a Live Performance Intelligence System
OxMaint replaces chiller log books with digital operating log trending, automated PM scheduling, oil analysis tracking, and EPA refrigerant log compliance — all linked to your chiller asset history. Book a demo to see the full chiller PM module.
Frequently Asked Questions: Commercial Chiller Maintenance
QHow often should a commercial chiller receive a full PM service?
Daily operating log monitoring should be maintained throughout the cooling season to catch approach temperature trends and efficiency drift early. A qualified technician should perform a monthly inspection covering refrigerant and electrical checks. Quarterly service should include tube brushing (when approach data indicates fouling) and water chemistry testing. Annual comprehensive service covers oil analysis, full refrigerant leak testing, motor insulation resistance testing, infrared thermography, and a performance report. Following this structure produces the operating log data needed to trend efficiency degradation and plan interventions before failures occur. Book a demo to see OxMaint's chiller PM scheduling configured for all four frequencies.
QWhat does chiller approach temperature tell you about maintenance needs?
Approach temperature is the difference between the chilled water leaving temperature and the refrigerant saturated evaporating temperature (on the evaporator side) or between the condenser water leaving temperature and the refrigerant saturated condensing temperature (on the condenser side). A clean, well-maintained chiller should have approach temperatures within 1 to 2°F of design at full load. Every 1°F of additional condenser approach adds approximately 1.5% to chiller energy consumption. An evaporator approach above 3°F indicates tube fouling; a condenser approach above 3°F on a water-cooled unit indicates condenser tube fouling or low water flow. Tracking approach temperature quarterly is the most reliable early-warning indicator of heat exchanger performance degradation.
QWhat should chiller oil analysis results look like, and when should the oil be changed?
Acceptable oil analysis results for a well-maintained chiller typically show viscosity within 10% of new oil specification, acid number below 0.1 mg KOH/g, moisture below 50 ppm, and wear metals including iron and copper each below 25 ppm. Elevated copper above 50 ppm suggests bearing or valve plate wear. Elevated iron above 50 ppm suggests rotor or housing wear in screw compressors. Moisture above 100 ppm indicates refrigerant contamination or system air infiltration. Oil should be changed when analysis results trigger any of these thresholds or when the oil has exceeded the manufacturer's recommended change interval — typically 5 years or 25,000 runtime hours, whichever comes first, for most centrifugal and screw chillers.
QWhat are the EPA refrigerant leak log requirements for commercial chillers?
Under EPA Section 608 regulations, owners of refrigeration equipment with more than 50 lbs of refrigerant charge are required to maintain a log of refrigerant additions. If the chiller leaks more than the applicable leak rate threshold (typically 10% of charge annually for commercial refrigeration), the owner is required to repair the leak within 30 days or develop a retrofit or retirement plan. Annual inspections are required, and all refrigerant additions must be performed by a Section 608-certified technician and documented. OxMaint's refrigerant leak log module tracks all refrigerant additions against the charge capacity, calculates annual leak rates, and flags when the system is approaching the action threshold.
QCan OxMaint trend chiller efficiency (kW/ton) over multiple PM cycles?
Yes. OxMaint stores kW input and cooling load readings entered during each operating log PM task against the chiller asset record and automatically calculates kW/ton at the recorded load point. Trend charts show kW/ton over time, normalised for load when sufficient data is available, enabling comparison of current season efficiency against previous seasons at equivalent load conditions. This trending capability is the most reliable way to schedule annual tube cleaning and compressor maintenance proactively — the kW/ton trend surface degradation 4 to 8 weeks before it becomes a visible fault or guest complaint. Book a demo to see the chiller efficiency trending dashboard.
Continue Reading: Chiller and HVAC Maintenance Resources
Ultimate HVAC Preventive Maintenance Checklist (2026)
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AHU and Fan Coil Unit Maintenance Checklist
Complete AHU and FCU inspection guide covering filters, coils, drain pans, belts, bearings, dampers, and controls with performance benchmarks and monthly to annual PM tasks.
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Hotel Indoor Air Quality Guide: HVAC Maintenance for Clean Air
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Hotel Emergency Preparedness Checklist: Generator and Life Safety Maintenance
Generator testing, emergency lighting verification, fire system inspection, and crisis readiness documentation — the complete maintenance checklist for hotel emergency systems.
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Run This Chiller Checklist Digitally on Your Next PM Visit
OxMaint deploys automated chiller PM checklists with operating log trending, oil analysis scheduling, EPA refrigerant log compliance, and automatic work order generation — configured for centrifugal, screw, and scroll chiller plants of any size. Book a 30-minute demo to see the full chiller PM workflow.
Operating Log Trending
Oil Analysis Scheduling
EPA Refrigerant Log
kW/ton Efficiency Tracking
Auto Work Order Generation