Preventive Maintenance, Service, and Documentation
Introduction
Preventive maintenance (PM) forms the backbone of refrigeration and air conditioning system reliability. For the Red Seal exam, you must master not only the technical procedures, but also documentation traceability, inspection intervals, and Canadian regulatory requirements. This chapter covers all the assessed competencies: planning, execution, preventive diagnostics, and record keeping.
A Red Seal technician doesn't just repair; they prevent, document, and communicate according to precise standards. Exam questions often focus on situations where neglected maintenance caused a breakdown — you must identify the root cause and the correct protocol.
1. Fundamental Principles of Preventive Maintenance
1.1 Definitions and Objectives
Preventive maintenance is a systematic program of inspections, cleanings, adjustments, and scheduled replacements, aimed at:
Maintaining equipment in its optimal operating condition
Extending the service life of components
Reducing unexpected breakdowns and production downtime
Ensuring the safety of people and property
Maintaining energy efficiency (COP, EER) near nameplate values
Predictive maintenance (vibration analysis, oil analysis, thermography) complements PM but is not the main focus of this chapter — be able to distinguish between them on the exam.
1.2 Types of Maintenance
| Type | Trigger | Example |
|---|
| Systematic preventive | Fixed schedule | Oil change every 2,000 hours |
| Condition-based preventive | Measured state | Condenser cleaning if ΔT > 8 °C |
| Corrective | Breakdown | Compressor replacement |
| Predictive | Trend analysis | Quarterly vibration analysis |
Golden rule: preventive maintenance is performed with the equipment shut down and locked out, except for measurements that require operation (pressures, amperages).
1.3 Risk Analysis and Prioritization
The CSA Z463 standard (Maintenance of Equipment) recommends a criticality analysis. On the exam, you'll often be asked to prioritize tasks. Criteria:
Safety impact (NH₃, R-290 leak)
Process impact (cold room at -25 °C)
Cost of failure vs. cost of maintenance
Regulatory requirements (mandatory annual inspection)
2. Critical Components and Their Inspections
2.1 Compressors
Reciprocating Compressors (Open and Semi-Hermetic)
Oil check: level on the sight glass (mid-height), color (dark brown = overheating), odor (burnt = wear)
Oil analysis: acidity (TAN < 0.5 mg KOH/g), moisture (dew point), metallic particles (iron, copper, aluminum)
Belts: tension (10 to 15 mm deflection with 40 N of pressure at mid-span), alignment (straight edge)
Relief valves: presence of seal wire, certification date (5 years for NH₃, 10 years for HFC per CSA B52)
Leaks: electronic detector, soap solution, UV lamp (with approved dye)
Belt tension calculation:
Deflection (mm) = (Distance between centers in mm) / 64
Example: center distance of 640 mm → deflection of 10 mm.
Screw Compressors
Oil filter: replacement based on operating hours (often 1,000 initial hours, then every 4,000 hours)
Shaft seal: visual inspection for oil traces
Capacity control valves: manual vs. automatic operation
Vibration: alarm threshold 4.5 mm/s (RMS) per ISO 10816
Centrifugal Compressors
Bearing clearance: measured with a dial indicator (axial clearance 0.05 to 0.15 mm per manufacturer)
Oil pump: differential pressure (typically 100 to 150 kPa above crankcase pressure)
Surge protection system: verify controller settings
2.2 Heat Exchangers
Air-Cooled Condensers
Fin cleaning: soft brush + compressed air (from inside to outside), or soapy water wash (max pressure 2,000 kPa, 30° angle)
Damaged fins: straighten with a fin comb (2 to 4 mm pitch depending on model)
Fans: balancing, belt tension, bearings (axial play < 0.4 mm)
Performance measurement: air ΔT = entering air - leaving air (normal: 8 to 12 °C for an air-cooled condenser)
Evaporative Condensers
Water treatment: hardness analysis (CaCO₃), pH (7.5 to 8.5), total dissolved solids (TDS < 1,500 ppm)
Water basin: cleaning, automatic bleed-off (concentration cycles 3 to 5)
Spray nozzles: inspection and clearing
Drift eliminators: condition of the vanes
Legionella warning: CSA Z800 (Water Quality in Cooling Towers) requires a water treatment log. On the exam, you'll be asked the analysis frequency: at least once per week for pH and chlorine.
Evaporators
Defrost: check heaters (continuity, amperage), defrost termination thermostats (opens at 10-15 °C), timers
Condensate drain pan: cleaning, drainage slope (1/4 inch per foot = 20 mm/m), trap (height = static pressure + 25 mm)
Fans: blade clearance (2 to 5 mm from the shroud), balancing
Frost accumulation: maximum thickness of 5 mm before defrost
2.3 Expansion Valves and Valves
Thermostatic Expansion Valve (TXV)
Bulb placement: at the evaporator outlet, on a horizontal line, at 3 o'clock or 9 o'clock (never at the bottom of the tube)
Measured superheat: suction line temperature - evaporating temperature (normal: 4 to 8 °C for R-134a, 5 to 10 °C for R-404A)
Adjustment: turning the adjustment stem clockwise increases superheat (more spring compression)
Superheat formula:
SH = Suction temperature - Evaporating temperature (saturation)
Example: Suction temperature = 2 °C, Evaporating temperature = -8 °C → SH = 10 °C (too high, open the TXV).
Solenoid Valves
Coil: continuity (resistance measurement), holding amperage (typically 80% of nameplate value)
Plunger: audible movement on energization, no humming
Differential pressure: minimum 35 kPa for reliable opening
Regulating Valves (EVR, CPR, ORI)
Operation: verify setpoint pressure with a calibrated gauge
Stem play: no leakage at the packing gland
2.4 Electrical Equipment
Contactors and Relays
Contacts: pitting, welding, discoloration (blue/violet = excessive arcing)
Coil: supply voltage (must be within ±10% of nameplate value)
Coil resistance: compare to manufacturer's value (at 20 °C)
Motor Protection
Overload relay: set according to nameplate full-load current (FLA × 1.25 for continuous-duty motors)
Electronic protection (ECM): verify parameters (starting current, ramp time)
Overload calculation:
Setting = FLA × 1.25 (service factor 1.15)
Example: 10 A motor, service factor 1.15 → setting = 10 × 1.25 = 12.5 A.
Wiring
Visual inspection: cracked insulation, loose connections (torque per bolt size)
Infrared thermography: detection of hot spots (ΔT > 10 °C compared to a healthy connection)
Grounding: continuity (resistance < 1 Ω), equipotential bonding
3. Specific Maintenance Procedures
3.1 Oil Drain and Replacement
Standard procedure (semi-hermetic compressor):
96.Pump down the compressor (close the discharge valve, open the suction valve)
97.Cut electrical power and lock out (lock + tag)
98.Isolate the compressor (service valves)
99.Recover refrigerant if necessary (depending on quantity and type)
100.Drain the oil through the drain plug (warm oil = better evacuation)
101.Fill through the fill port with new oil (same type and viscosity)
102.Purge the air (evacuate to 500 microns, then break vacuum with refrigerant)
103.Return to service and check the oil level after 30 minutes of operation
Oil types:
| Refrigerant | Oil | ISO Viscosity |
|---|
| R-134a | POE | 32 or 68 |
| R-404A / R-507 | POE | 32 |
| R-22 | Mineral / alkylbenzene | 32 |
| R-717 (NH₃) | Mineral | 68 |
| R-290 (propane) | Mineral / POE | 32 |
Trap to avoid: never mix mineral and POE oils — they are not miscible and will cause a wax plug in the expansion valve.
3.2 Cleaning Water-Cooled Condensers (Shell-and-Tube)
Chemical cleaning (descaling): phosphoric acid (5-10%) or citric acid, circulated for 30 to 60 minutes at 50 °C
Mechanical cleaning: rotating brushes (nylon or steel depending on tube material)
Post-cleaning verification: water ΔT (inlet-outlet) must return to under 5 °C; water pressure drop within manufacturer's values
Condenser efficiency calculation:
Efficiency (%) = (Water outlet temp - Water inlet temp) / (Condensing temp - Water inlet temp) × 100
A clean condenser has an efficiency of 60 to 80%.
3.3 Leak Checking
Methods:
| Method | Sensitivity | Application |
|---|
| Soap solution | 10⁻⁴ mL/s | Joints, fittings |
| Electronic detector (halogen) | 10⁻⁶ mL/s | HFC, HCFC |
| UV lamp + dye | 10⁻⁵ mL/s | Visual location |
| Nitrogen + pressure | 10⁻³ mL/s | Strength test |
| Helium (mass spectrometer) | 10⁻⁹ mL/s | Fine leak testing |
Regulatory requirements: the Ozone-Depleting Substances Regulations (ODSR) requires repair of leaks greater than 10% per year (systems > 50 kg charge). Leak records must be kept for 5 years.
3.4 Checking Pressure Switches and Thermostats
High-pressure switch (HP): trips at the setpoint (e.g., 2,400 kPa for R-404A), manual or automatic reset
Low-pressure switch (LP): trips at the minimum value (e.g., 50 kPa for R-134a), differential of 20 to 30 kPa
Room thermostat: accuracy ±0.5 °C, hysteresis 1 to 2 °C
Oil safety thermostat: trips at 30-40 kPa oil differential
Verification procedure: use a calibrated gauge (accuracy ±0.5%), compare values, adjust if necessary, seal the settings.
4. Documentation and Traceability
4.1 Maintenance Records
Every intervention must be documented with:
Date and time of the intervention
Technician's name (signature)
Equipment involved (serial number, location)
Description of the intervention (tasks performed)
Measurements taken (pressures, temperatures, amperages)
Parts replaced (part numbers, quantities)
Refrigerant added or removed (type, quantity)
Duration of the intervention
Observations and recommendations
Red Seal requirement: records must be legible, complete, and signed. An incomplete file is considered non-compliant during a verification.
4.2 Safety Data Sheets (SDS)
Every chemical product used (descaler, degreaser, refrigerant) must have its SDS accessible in the workplace
The SDS must be dated within the last 3 years (WHMIS 2015)
The technician must know: hazards, first aid measures, personal protective equipment (PPE)
4.3 Lockout/Tagout and Labeling
Lockout tag: name, date, reason, signature — affixed to the disconnecting means
Lock: one per worker (multiple-lock system with a hasp)
Verification of absence of voltage: approved tester, tested on a known live source before and after
Lockout/tagout procedure:
147.Notify affected personnel
148.Shut down the equipment (off position)
149.Isolate all energy sources (electrical, mechanical, thermal, chemical)
150.Apply locks and tags
151.Dissipate residual energy (capacitors, springs, pressure)
152.Verify the absence of energy (test for start)
153.Perform the intervention
154.Remove locks, return to service, notify personnel
4.4 Service Reports and Communication
The service report must include:
Reported symptom from the customer (in their own words)
Diagnosis (identified root cause)
Correction (actions taken)
Verification (results after intervention)
Recommendations (future maintenance, improvements)
Trap to avoid: never write "adjusted" without specifying the measured values. A professional report contains numbers.
5. Canadian Regulatory Requirements
5.1 Canadian Electrical Code, Part I (CE Code)
Rule 8-200: conductors and equipment must be protected against overcurrent (fuses or circuit breakers)
Rule 26-200: motors must have overload protection (thermal or electronic relays)
Rule 26-248: hermetic compressors are treated as motors (rated current = nameplate current)
Rule 2-100: work must be performed by qualified persons
Practical application: during maintenance, verify that fuses are of the correct rating (never replace a fuse with a higher rating). Rule 8-200 requires that protection be coordinated with conductor capacity.
5.2 CSA B52 (Mechanical Refrigeration Systems)
Article 4.2: relief valves must be certified and dated
Article 5.1: machinery rooms must have emergency ventilation
Article 6.3: piping must be identified (color, label)
Article 7.1: pressure tests must be documented
5.3 CSA B149.1 (Natural Gas and Propane)
Applies to systems using flammable refrigerants (R-290, R-600a):
Article 6.2: ventilation must comply (4 air changes/hour minimum)
Article 6.4: leak detectors must be installed 300 mm from the floor (propane is heavier than air)
Article 7.3: equipment must be certified for the gas being used
5.4 Ozone-Depleting Substances Regulations (ODSR)
Article 5: prohibition on using CFCs (R-11, R-12) — mandatory replacement
Article 6: HCFCs (R-22) are in phase-down — import prohibited since 2020
Article 7: HFCs (R-134a, R-404A) are regulated — progressive reduction (Kigali Amendment)
Article 8: recovery obligation (minimum 80% of refrigerant)
Article 9: register of recovered, recycled, and destroyed quantities
Certification requirement: any technician handling refrigerants must hold a certificate of competence (Ozone Depletion Prevention Program). On the exam, you'll be asked the validity period: 5 years.
5.5 CSA Z317.1 (Health Care Facilities)
For work in hospitals: specific requirements for filtration (HEPA), room differential pressure, and documentation of interventions on HVAC systems.
6. Efficiency Calculations and Measurements
6.1 Energy Efficiency
Coefficient of performance (COP):
COP = Cooling capacity (kW) / Power input (kW)
EER (Energy Efficiency Ratio):
EER = Cooling capacity (BTU/h) / Power input (W)
Conversion: 1 kW = 3,412 BTU/h
Example: a system produces 10 kW of cooling and consumes 3 kW → COP = 10/3 = 3.33; EER = (10 × 3,412)/3,000 = 11.37.
6.2 Condensing Temperature and Superheat
Condensing temperature: measured on the high-pressure gauge, converted to saturation temperature (refrigerant chart)
Subcooling: condensing temperature - liquid temperature at condenser outlet (normal: 5 to 10 °C)
Superheat: suction temperature - evaporating temperature (normal: 4 to 10 °C)
Quick diagnostic:
| Symptom | Superheat | Subcooling | Probable cause |
|---|
| TXV underfeeding | High (> 10 °C) | Normal | Expansion valve too closed, plugged filter |
| TXV overfeeding | Low (< 4 °C) | Normal | Expansion valve too open, poorly mounted bulb |
| Dirty condenser | Normal | Low (< 3 °C) | Lack of heat exchange |
| Insufficient charge | High | Low | Refrigerant leak |
6.3 Air Volume and Flow Rate
Airflow (CFM):
CFM = (Sensible heat in BTU/h) / (1.08 × air ΔT)
Example: 36,000 BTU/h, ΔT = 20 °F → CFM = 36,000 / (1.08 × 20) = 1,667 CFM.
In SI units:
Flow rate (m³/s) = Sensible heat (kW) / (1.2 × ΔT in °C)
Example: 10 kW, ΔT = 10 °C → Flow rate = 10 / (1.2 × 10) = 0.83 m³/s.
6.4 Air Change Rate
Machinery rooms (CSA B52):
Ventilation = 0.5 m³/s per 100 kg of refrigerant, minimum 0.3 m³/s.
Calculation: room containing 200 kg of R-404A → ventilation = 200/100 × 0.5 = 1.0 m³/s.
7. Traps to Avoid
218.Confusing preventive and corrective maintenance: PM is planned, corrective is reactive. On the exam, you'll be given a scenario — identify the type.
219.Neglecting lockout/tagout: every intervention on energized or pressurized equipment requires complete lockout. A trick question will describe a technician who "works fast" without locks — that's always wrong.
220.Forgetting to verify the absence of voltage: after lockout, you must test for the absence of voltage with an approved tester, on a known live source before and after.
221.Mixing oils: mineral + POE = incompatibility. Always check the existing oil type before topping up.
222.Confusing superheat and subcooling: superheat is measured on the suction line, subcooling on the liquid line. Reversing the diagnosis is fatal.
223.Ignoring documentation requirements: maintenance without a signed report is considered not performed. Records must be kept for 5 years (ODSR).
224.Using a higher-rated fuse: violation of CE Code Rule 8-200. The rating must match the original protection.
225.Forgetting valve certification dates: relief valves must be certified (CSA B52) — an expired valve is a major non-conformity.
226.Not checking ΔT after cleaning: condenser cleaning must be validated by a measurement (water ΔT < 5 °C, air ΔT 8-12 °C).
227.Working on a system containing NH₃ without appropriate PPE: NH₃ cartridge respirator, nitrile gloves, sealed goggles.
8. Summary
Preventive maintenance is systematic, planned, and documented — it aims to prevent failures, not repair them.
Critical components (compressors, heat exchangers, expansion valves, electrical equipment) have specific inspection procedures with reference values (superheat 4-10 °C, subcooling 5-10 °C, condenser ΔT 8-12 °C).
Documentation is mandatory: maintenance records, service reports, SDS, lockout labeling. Undocumented work is unfinished work.
Canadian standards (CE Code Part I, CSA B52, CSA B149.1, ODSR) impose precise requirements: electrical protection, valve certification, refrigerant recovery, leak records.
Efficiency calculations (COP, EER), airflow (CFM), and ventilation (m³/s per kg of refrigerant) are common on the exam — master the formulas and conversions.
Safety is non-negotiable: lockout/tagout, PPE, verification of absence of voltage, refrigerant handling per regulations.
9. Traps to Avoid (Exam Recap)
| Trap | Consequence | Best Practice |
|---|
| Confusing PM and corrective | Wrong answer | Identify the trigger (schedule vs. breakdown) |
| Forgetting lockout/tagout | Major non-conformity | Always lock + tag + verify |
| Mixing oils | Compressor damage | Check existing oil type |
| Reversing superheat/subcooling | Wrong diagnosis | SH = suction, SC = liquid |
| Oversized fuse | Fire hazard | Respect original rating (Rule 8-200) |
| Uncertified valve | CSA B52 non-conformity | Check certification date |
| Incomplete report | Work considered not done | Document all measurements |
| Ignoring ΔT after cleaning | Ineffective cleaning | Measure before/after |
| Working without PPE on NH₃ | Serious risk | Mask, gloves, goggles |
| Not keeping records for 5 years | ODSR violation | Archive systematically |
10. Final Exam Tips
Read each question twice: Red Seal questions often contain distractors (useless information) — identify the relevant data.
Watch your units: the Red Seal uses SI (kPa, °C, kW) but some questions give imperial values (PSI, °F, BTU/h) — know how to convert quickly.
Memorize key values: superheat 4-10 °C, subcooling 5-10 °C, condenser ΔT 8-12 °C, evaporator ΔT 8-12 °C, machinery room ventilation 0.5 m³/s per 100 kg.
Know your standards: CE Code Part I (Rules 8-200, 26-200), CSA B52 (valves, machinery rooms), CSA B149.1 (flammable refrigerants), ODSR (recovery, records).
Practice the calculations: COP, EER, CFM, airflow, ventilation — these questions are almost guaranteed.
Review the procedures: oil change, condenser cleaning, leak checking, lockout/tagout — you'll be asked for the exact order of steps.
Good luck! A Red Seal technician is a professional who prevents, documents, and secures — that's exactly what this chapter prepares you to demonstrate.
