Refrigerants, Oils, and Environmental Regulations

Chapter Introduction

This chapter covers one of the pillars of the refrigeration and air conditioning mechanic trade: mastery of refrigerants, lubricating oils, and the Canadian regulatory framework that governs them. For the Red Seal exam, you must not only know the thermodynamic properties of refrigerants, but also handling procedures, charge calculations, oil compatibility, and current legal requirements. This chapter is designed to prepare you directly for typical exam questions.

Refrigerant Classification and Properties

ASHRAE Numbering and Nomenclature

The ASHRAE 34 standard (refrigerant designation and safety classification) is the international reference. The numbering system is based on the chemical structure of the molecule. The R-XXX code breaks down as follows:

First digit (rightmost): number of fluorine (F) atoms

Second digit: number of hydrogen (H) atoms + 1

Third digit: number of carbon (C) atoms − 1 (omitted if the result is 0)

Fourth digit: number of chlorine (Cl) atoms — only for CFCs and HCFCs

Example: R-134a (CH₂FCF₃)

Carbons: 2 → third digit = 2 − 1 = 1

Hydrogens: 2 → second digit = 2 + 1 = 3

Fluorines: 4 → first digit = 4

Result: R-134. The letter "a" indicates an isomer (in this case, tetrafluoroethane).

Example: R-22 (CHClF₂)

Carbons: 1 → third digit omitted

Hydrogens: 1 → second digit = 1 + 1 = 2

Fluorines: 2 → first digit = 2

Chlorine: 1 → fourth digit = 1

Result: R-22.

Lowercase letters (a, b, c) designate positional isomers. Uppercase letters (A, B) in the safety classification indicate toxicity: A = non-toxic, B = toxic.

ASHRAE 34 Safety Classification

Class	Toxicity	Flammability	Examples
A1	Non-toxic	Non-flammable	R-134a, R-410A, R-22
A2	Non-toxic	Flammable (low)	R-152a, R-1234yf
A3	Non-toxic	Highly flammable	R-290 (propane), R-600a
B1	Toxic	Non-flammable	R-123
B2	Toxic	Flammable	R-142b

Exam point: R-410A is a zeotropic blend of R-32 (HFC) and R-125 (HFC), classified as A1. R-1234yf (HFO) is classified as A2L (low flammability) — this "L" subclass is often tested.

Pure Refrigerants vs. Blends

Pure: a single chemical compound (R-134a, R-22; R-410A is a blend, but R-32 is pure).

Zeotropic blends: temperature glide is non-zero. Evaporation and condensation temperatures vary at constant pressure. Examples: R-404A, R-407C, R-410A.

Azeotropic blends: behave like a pure fluid — glide is zero or nearly zero. Examples: R-500, R-502 (obsolete).

Temperature glide (ΔT glide): the difference between the dew point temperature and the bubble point temperature at constant pressure. For a zeotropic blend, use the mean temperature for heat exchanger sizing.

Fractionation: during a leak, the composition of a zeotropic blend changes — the more volatile component escapes first. Golden rule: for a zeotropic blend, always recharge in the liquid phase to preserve the composition.

Refrigerant	Type	Glide (°C)	Typical Application
R-134a	Pure HFC	0	Commercial refrigeration, automotive
R-410A	Zeotropic HFC	~0.1	Residential air conditioning
R-404A	Zeotropic HFC	~0.5	Low-temperature commercial refrigeration
R-407C	Zeotropic HFC	~6.0	R-22 replacement in air conditioning
R-290	Pure HC (propane)	0	Commercial refrigeration (small)
R-1234yf	Pure HFO	0	Automotive air conditioning

Refrigeration Lubricating Oils

Role of Oil

Oil provides compressor lubrication, sealing of pistons and bearings, and heat removal. It must be compatible with the refrigerant, the circuit materials, and the operating temperatures.

Oil Types and Compatibility

Oil Type	Abbreviation	Compatibility	Typical Viscosity (ISO)
Mineral	MO	CFC, HCFC (R-12, R-22)	32, 68
Alkylbenzene	AB	HCFC, HFC (transition)	32, 46
Polyol ester	POE	HFC (R-134a, R-410A, R-404A)	32, 46, 68
Polyalkylene glycol	PAG	HFC (automotive)	46, 100, 150

Critical points for the exam:

Mineral oils are not miscible with HFCs. Using mineral oil with R-134a causes poor oil circulation, oil accumulation in the evaporator, and compressor failure.

POE oils are hygroscopic: they absorb moisture from the air very quickly. An open container of POE oil left exposed to air can absorb enough moisture in a few minutes to exceed the acceptable limit (50 ppm). Always reseal containers immediately.

PAG oils are used almost exclusively in piston compressors for automotive air conditioning. They are also hygroscopic and electrically conductive — never use them in a hermetic compressor with an electric motor.

Viscosity and Viscosity Index

Viscosity is the resistance to flow. It decreases with temperature. The viscosity index (VI) indicates the stability of viscosity with temperature — the higher the VI, the less the viscosity changes.

Rule of thumb: for a low evaporation temperature (−40 °C), choose a lower viscosity oil (ISO 32) to ensure oil return. For high temperatures (air-cooled condenser at 50 °C), choose a higher viscosity (ISO 68).

Oil Return

Oil return is a major issue in refrigeration. Factors influencing oil return:

Miscibility: the more miscible the oil is in the refrigerant, the better the return.

Gas velocity in suction lines: a minimum velocity of 4 to 6 m/s in vertical risers is required to carry the oil.

Oil traps (P-traps): required every 3 to 4 metres on vertical risers in the suction line.

Low evaporation temperature: viscosity increases, making oil return more difficult.

Gas velocity calculation in a line:

Velocity (m/s) = Volumetric flow rate (m³/s) ÷ Line cross-sectional area (m²)

Area = π × (D/2)² where D is the inside diameter in metres.

Example: Volumetric flow rate of 0.02 m³/s in a line with a 50 mm (0.05 m) inside diameter.

Area = 3.1416 × (0.025)² = 0.001963 m²

Velocity = 0.02 ÷ 0.001963 = 10.2 m/s — acceptable for oil return.

Canadian Environmental Regulations

Canadian Environmental Protection Act (CEPA)

The CEPA (1999) is the primary legislative framework. It regulates ozone-depleting substances (ODS) and their substitutes. The Ozone-depleting Substances and Halocarbon Alternatives Regulations (ODSHAR) is the implementing regulation.

Key ODSHAR Requirements

Mandatory certification: any person who handles, installs, repairs, or disposes of systems containing halocarbons must hold a certificate of competency (issued by a training organization accredited by Environment and Climate Change Canada — ECCC).

Mandatory recovery: before any repair or dismantling of a system, the refrigerant must be recovered into an approved cylinder.

Leak limits: systems containing more than 50 kg of refrigerant must be checked for leaks according to a specific schedule:

Hermetic systems: every 12 months

Systems with open compressors: every 6 months

Systems with automatic leak detection: every 24 months

Record keeping: quantities of refrigerant purchased, used, recovered, and disposed of must be recorded.

CFC and HCFC bans: production and import of CFCs have been banned since 1996. For HCFCs (R-22), the import ban has been in effect since 2020, with a complete phase-out.

Halocarbon Regulations (2022)

This new regulation (in force since 2023) aims to reduce HFC emissions by 85% by 2036 compared to 2011-2013 levels. Key points:

GWP (global warming potential): high-GWP HFCs (R-404A: 3922) are being phased out progressively.

Installation bans: certain systems with high-GWP refrigerants are prohibited for new installations according to specific timelines.

Labelling: systems must be labelled with the refrigerant type and charge.

Canadian Electrical Code, Part I

The Canadian Electrical Code, Part I (CSA C22.1 standard) contains requirements for electrical installations in areas where flammable refrigerants are present. Key rules:

Rule 8-200: classification of hazardous locations — areas around systems containing flammable refrigerants (A2L, A3) must be classified as Zone 1 or Zone 2.

Rule 18-000: requirements for wiring in hazardous locations — use of sealed conduits, approved junction boxes, and explosion-proof equipment if required.

Rule 26-700: requirements for electric motors in hazardous locations.

Exam point: for an R-290 (propane, A3) system, electrical equipment within a 1 m zone around the system must be certified for Class I, Division 2 (or Zone 2). Standard switches, receptacles, and motors are prohibited in this zone.

CSA B149.1 — Natural Gas and Propane Code

The CSA B149.1 standard applies to systems using hydrocarbons as refrigerants (R-290, R-600a). Key requirements:

Charge limit: the maximum propane charge in an occupied space is limited to 150 g for self-contained appliances, or calculated according to the room area (formula based on the lower flammability limit — LFL).

Ventilation: rooms containing propane systems must have adequate ventilation to prevent gas accumulation in the event of a leak.

Leak detection: required for charges exceeding 150 g in occupied spaces.

Charge Calculations and Superheat/Subcooling

Superheat

Superheat is the difference between the actual vapour temperature at the evaporator outlet and the saturation temperature corresponding to the evaporation pressure.

Formula: Superheat = T_vapour − T_saturation

Example: R-134a, evaporation pressure of 200 kPa (saturation temperature = −10 °C). Measured temperature at the evaporator outlet = −2 °C.

Superheat = −2 − (−10) = 8 °C — typical value for a thermostatic expansion valve.

Subcooling

Subcooling is the difference between the saturation temperature (condensation) and the actual liquid temperature at the condenser outlet.

Formula: Subcooling = T_saturation − T_liquid

Example: R-410A, condensing pressure of 2500 kPa (saturation temperature = 40 °C). Measured liquid temperature = 33 °C.

Subcooling = 40 − 33 = 7 °C — typical value (5 to 10 °C).

Saturation Temperature Table (excerpts)

Refrigerant	Pressure (kPa)	Saturation Temperature (°C)
R-134a	100	−26.4
R-134a	200	−10.1
R-134a	400	8.9
R-410A	800	6.4
R-410A	2000	34.2
R-22	300	−6.7
R-22	1500	39.1

Exam tip: you will never be asked to memorize these tables. You will be provided with a pressure-temperature table or a P-h diagram. You must know how to read these tables and apply the formulas.

Refrigerant Handling Procedures

Recovery

Recovery involves removing refrigerant from a system into an approved storage cylinder, without treatment. Procedure:

107.Verify that the recovery cylinder is empty and approved for the type of refrigerant.

108.Connect the manifold with quick-coupler hoses — check for leaks.

109.Use a certified recovery machine (conforming to AHRI 740 standard).

110.Recover until the system pressure reaches 0 kPa (or the required negative pressure depending on the system type).

111.Weigh the cylinder before and after to determine the recovered quantity.

Safety rule: never fill a cylinder beyond 80% of its volume capacity (or 90% for cylinders with a dip tube). Liquid expands with temperature — an overfilled cylinder can explode.

Recycling

Recycling is the treatment of recovered refrigerant by filtration and drying for reuse in the same system or another system belonging to the same owner. AHRI 700 standards define acceptable purity levels.

Reclaiming

Reclaiming is a more extensive treatment (distillation) that returns the refrigerant to new-product purity (AHRI 700 standard). This process is carried out by specialized facilities.

Charging a System

Liquid-phase charging: mandatory for zeotropic blends (R-410A, R-404A). The cylinder must be inverted (valve at the bottom) or use a dip tube.

Vapour-phase charging: acceptable for pure refrigerants (R-134a) on small charges, but slow and risky (moisture).

Common error: charging R-410A in the vapour phase changes the blend composition in the cylinder and in the system — the R-32 (more volatile) escapes first, leaving a blend depleted of R-32 in the cylinder.

Leak Detection

Detection Methods

Method	Sensitivity	Application
Electronic detector	0.1 to 5 g/year	All refrigerants
Soap solution	10 to 50 g/year	Accessible points, joints
Halide torch (old)	10 g/year	CFC only (obsolete)
Nitrogen under pressure	—	Leak testing after repair
Ultrasonic	—	Detection of major leaks

Nitrogen testing procedure: pressurize the system with dry nitrogen (N₂) to the service pressure (generally 1.5 × the maximum operating pressure). Never use oxygen — risk of explosion with oil.

Safety rule: never exceed the system design pressure. Use a pressure regulator on the nitrogen cylinder.

Pitfalls to Avoid

129.Confusing superheat and subcooling: superheat is measured at the evaporator (vapour), subcooling at the condenser (liquid). Always reread the question to identify the measurement location.

130.Charging a zeotropic blend in the vapour phase: this is the most serious error. The composition changes and system performance degrades.

131.Using mineral oil with an HFC: total incompatibility. The oil does not return to the compressor and the system becomes contaminated.

132.Forgetting that POE oils are hygroscopic: a container left open for a few minutes can compromise the entire system. Moisture causes acid formation and compressor failure.

133.Filling a recovery cylinder beyond 80%: risk of hydraulic explosion. Always weigh the cylinder.

134.Ignoring temperature glide: for a zeotropic blend, the saturation temperature is not unique. Use the mean temperature for calculations.

135.Confusing safety classifications: A1 = non-toxic/non-flammable; A2L = low flammability; A3 = highly flammable. R-290 (propane) is A3, not A2.

136.Forgetting record-keeping requirements: CEPA requires detailed record keeping. An exam question may ask about leak check frequency (12 months for hermetic, 6 months for open compressor).

137.Using oxygen for leak testing: risk of explosion. Always use dry nitrogen.

138.Neglecting oil return in vertical risers: minimum velocity of 4 to 6 m/s is required. An oil trap is needed every 3 to 4 metres.

Summary

ASHRAE 34 nomenclature: the R-XXX code encodes the chemical structure (F, H, C, Cl). Lowercase letters = isomers, uppercase letters = toxicity (A/B) and flammability (1/2/3).

Zeotropic blends: non-zero temperature glide, possible fractionation, liquid-phase charging mandatory.

Oils: mineral (CFC/HCFC), POE (HFC), PAG (automotive). POE and PAG are hygroscopic — moisture protection is essential.

Regulations: CEPA (1999) and ODSHAR require certification, recovery, leak checks (12/6/24 months depending on system type), and record keeping.

Canadian Electrical Code, Part I: rules 8-200, 18-000, and 26-700 for hazardous locations with flammable refrigerants.

CSA B149.1: charge limits for hydrocarbons (150 g in occupied spaces, or calculated according to LFL).

Calculations: superheat = T_vapour − T_saturation; subcooling = T_saturation − T_liquid. Know how to read a pressure-temperature table.

Safety: recovery cylinder max 80%; never use oxygen for testing; dry nitrogen only.

Practice Questions (Red Seal style)

151.What is the approximate temperature glide of R-410A?

a) 0 °C b) 0.1 °C c) 6 °C d) 10 °C

Answer: b) — R-410A is a near-azeotropic blend.

154.An R-134a system operates with an evaporation pressure of 200 kPa (saturation at −10 °C). The measured temperature at the evaporator outlet is −4 °C. What is the superheat?

a) 4 °C b) 6 °C c) 10 °C d) 14 °C

Answer: b) — Superheat = −4 − (−10) = 6 °C.

157.Which oil is compatible with R-410A?

a) Mineral b) Alkylbenzene c) POE d) PAG

Answer: c) — HFCs require POE oils.

160.According to ODSHAR, how often must a hermetic system containing more than 50 kg of refrigerant be checked for leaks?

a) Every 3 months b) Every 6 months c) Every 12 months d) Every 24 months

Answer: c) — 12 months for hermetic, 6 months for open compressor, 24 months with automatic detection.

163.What is the maximum propane (R-290) charge in an occupied space according to CSA B149.1?

a) 50 g b) 150 g c) 500 g d) 1 kg

Answer: b) — 150 g for self-contained appliances.

This chapter covers the essentials for passing questions on refrigerants, oils, and regulations. Review the tables, memorize the classifications and check frequencies, and practice superheat and subcooling calculations. Good luck with your preparation!

Refrigerants, Oils, and Environmental Regulations