Chillers account for up to 40% of a commercial building's total energy consumption — making them simultaneously the highest-value and highest-risk HVAC asset in any facility. An unplanned chiller shutdown during peak summer demand costs an average of $16,000 in emergency labor, parts, and lost productivity. Yet the majority of these failures trace back to skipped inspections, missed lubrication cycles, and refrigerant charge drift that a structured maintenance program would have caught weeks earlier. This guide covers centrifugal, screw, and scroll chillers across every service frequency — daily through annual — with type-specific tasks, performance thresholds, and priority classification. Sign up free to convert this checklist into automated digital work orders, or book a demo to see Oxmaint configured for your chiller plant.
40%
Of a building's total energy consumed by chiller systems
$16,000
Average cost of an unplanned chiller shutdown during peak demand
45%
Fewer unplanned outages in facilities with structured PM programs
$90,000
Max compressor repair cost that a $50 oil analysis test can prevent
Chiller Type Comparison: Maintenance Profile at a Glance
Centrifugal, screw, and scroll chillers each have distinct maintenance requirements. Understanding the differences before building your PM schedule prevents misapplied tasks and missed type-specific failure modes. Book a demo to see how Oxmaint manages type-specific checklists across a mixed chiller plant.
Centrifugal
100–3,000+ tons
CompressorDynamic — impeller / diffuser
Oil systemRequired (except magnetic bearing)
Unique riskSurge — pre-rotation vane wear
Key taskOil / refrigerant spectrographic analysis
Efficiency0.45–0.7 kW/ton at full load
Screw
20–500 tons
CompressorPositive displacement — twin rotor
Oil systemRequired — oil separator critical
Unique riskOil carry-over — slide valve wear
Key taskOil separator element replacement
Efficiency0.6–0.9 kW/ton at full load
Scroll
3–60 tons
CompressorPositive displacement — orbiting scroll
Oil systemInternal — no separate circuit
Unique riskRefrigerant floodback — tip seal wear
Key taskRefrigerant charge verification
Efficiency0.7–1.1 kW/ton at full load
Daily Chiller Maintenance Checklist
Daily 15–20 minutes per unit · Applies to all chiller types
Control panel and fault log review — check for active faults, warnings, or lockout codes; a silenced fault that is not corrected will recur and cause safety shutdown at the worst possible operating moment
Critical
Log suction and discharge pressure — compare to manufacturer design specification; flag if water-cooled condenser exceeds 200 psig; record chilled water supply and return temperatures; calculate delta-T against design value
Critical
Compressor oil level and pressure — check oil level in sight glass; verify oil pressure differential is within manufacturer specification (typically 25–45 PSI above suction pressure for centrifugal/screw units); low oil pressure trips safety shutdown
Critical
Refrigerant sight glass inspection — check for bubbles which indicate low charge or moisture in the system; record any observation; a system with visible bubbles at the sight glass is operating below design cooling capacity
High
Check compressor motor running amps vs. rated full-load amperage (FLA) — amperage consistently above FLA indicates a developing mechanical or electrical fault; record all three phases and note any phase imbalance greater than 5%
High
Listen and feel for abnormal vibration or sound — identify cavitation, rattling, or squealing; feel for excessive vibration at pump housing, compressor body, and piping connections; document any deviation from normal operating sound profile
High
Confirm safety controls armed — verify high-pressure cutout, low-pressure cutout, and motor thermal protection are not in bypass or manual override; document any active bypass conditions with reason and authorized sign-off
Medium
Weekly Chiller Maintenance Checklist
Weekly 30–45 minutes per unit · All chiller types
Electrical connections and contactors — verify starter and control panel connections are tight and free of heat discoloration; check contactors for pitting or arc marks; loose electrical connections are a leading cause of compressor failure in all chiller types
Critical
Variable frequency drive (VFD) operation — verify VFD output voltage and current balance; check for fault codes; inspect internal cooling fans; a VFD fault on a centrifugal chiller forces full-speed operation, eliminating all energy-saving load modulation
High
Condenser and chilled water pump operation — check pump motor temperature, bearing condition, and flow rate; verify strainer differential pressure is within limits; reduced flow reduces heat transfer and degrades chiller efficiency rapidly
High
Cooling tower condition — inspect basin level, bleed-off valve operation, and fan motor; verify water treatment dosing pump is operating; Legionella risk is elevated in warm recirculating systems — document water quality readings for compliance
High
Review BMS and remote monitoring data — pull trend data from chiller controller to identify setpoint deviations, capacity limitations, and approaching maintenance thresholds that may not trigger visible alarms during normal operation
Medium
Preventive Maintenance
Chiller Asset Tracking
Auto Work Orders
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Monthly Chiller Maintenance Checklist
Monthly Requires certified HVAC technician for refrigerant tasks
Refrigerant leak check — inspect all joints, valve stems, and brazed connections with electronic leak detector; EPA Section 608 requires leak repair within 30 days when a system with 50+ lbs charge exceeds the annual leak rate threshold
Critical
Evaporator and condenser approach temperature — calculate approach delta-T; a 0.001-inch scale layer on condenser tubes cuts heat transfer efficiency by 10% and adds 6–8% to energy cost every month it is untreated; tube fouling is detected earliest through approach temperature trending
Critical
Safety controls functional test — simulate fault conditions where safe to do so; test high-pressure cutout, low-pressure cutout, freeze protection, and motor thermal overload; document test results against set-point specifications; file in asset compliance record
High
Purge unit run time (centrifugal only) — excessive purge runtime indicates an active refrigerant leak or air infiltration; log purge cycles and cumulative runtime; trending purge data is one of the most reliable leading indicators of refrigerant system integrity
High
Slide valve modulation — screw chillers only; verify slide valve modulates smoothly across full capacity range (10–100%); check discharge temperature — screw units should stay continuously below 220°F; discharge temperature above limit accelerates oil degradation
High
Refrigerant moisture content — measure moisture with a sight glass test kit or log moisture indicator color; moisture in the refrigerant circuit forms acid that attacks copper surfaces and contaminates compressor oil; replace filter-drier if indicator shows wet
Medium
Annual Chiller Maintenance Checklist
Annual Planned shutdown required · Certified technician mandatory
Oil and refrigerant spectrographic analysis (centrifugal and screw) — submit samples for lab analysis every 6 months minimum; analysis detects iron, copper, and aluminum wear particles from internal compressor components weeks before catastrophic bearing failure; a $50 lab test prevents a $60,000–$90,000 compressor replacement
Critical
Motor winding megohm test — perform insulation resistance test on compressor motor windings; document and trend results annually; readings below 10 megohms require immediate motor inspection before next startup attempt; baseline measurement at installation is essential for trending
Critical
Condenser and evaporator tube inspection — eddy-current testing of heat exchanger tubes every 3–5 years; mechanical brush or chemical tube cleaning annually; tube fouling and pitting are progressive — early detection through annual inspection avoids emergency retube during peak season
Critical
Pre-rotation vane (IGV) inspection — centrifugal chillers only; inspect vanes for wear, sticking, or actuator slop; verify surge protection controls are calibrated and operating limits are current; IGV failure causes chiller surge — an uncontrolled compressor aerodynamic stall
High
Oil separator element replacement — screw chillers only; replace oil separator element per OEM interval (typically 12 months or 8,000 operating hours); a degraded separator allows oil carry-over into the refrigerant circuit, fouling heat exchanger tubes and reducing efficiency
High
Full refrigerant charge verification — recover, weigh, and recharge to OEM specification; verify superheat and subcooling at rated operating conditions; check and replace filter-drier; perform standing pressure test before recharge to confirm system integrity
High
Gearbox inspection (centrifugal) — check gearbox oil level and condition; collect oil sample for spectrographic analysis; inspect gear mesh pattern if accessible; a failed gearbox on a centrifugal chiller is a total loss event — early detection through oil trending is the only economical defense
Medium
Key Performance Parameters to Log Every Day
Chilled Water Supply Temp
Design setpoint ±1°F
Deviation over 2°F — investigate load or refrigerant
Chilled Water Delta-T
8–12°F typical design
Low delta-T indicates low flow or coil fouling
Condenser Approach Temp
Less than 5°F approach
Rising approach = tube fouling; clean immediately
kW/ton Efficiency
Below 0.8 kW/ton (centrifugal)
Above 0.8 kW/ton — fouling or charge issue
Oil Pressure Differential
25–45 PSI above suction
Low ΔP — immediate safety shutdown risk
Motor Suction Superheat
8–12°F at suction inlet
High superheat = low charge or restriction
Preventive Maintenance · Chiller Asset Tracking · Automated Work Orders
Your Chillers. Every Interval. Always On Schedule.
Oxmaint turns this checklist into type-specific digital PM templates — daily, weekly, monthly, and annual — with automatic work order escalation for out-of-range readings and full audit-ready compliance records.
3 types
Centrifugal, screw, and scroll — all pre-configured
Auto
Work orders on out-of-range readings
5 weeks
From signup to first digital round completed
0 paper
No clipboards. No manual report writing.
