Red Seal Appliance Service Technician cheat sheet

WHMIS 2016 (GHS-aligned) uses three signal elements: hazard pictograms, signal words (Danger or Warning), and hazard statements; Safety Data Sheets have 16 fixed sections, with Section 8 covering exposure controls and PPE.

Refrigerant exposure limits: R-410A and R-32 have an AEL (acceptable exposure limit) of 1000 ppm over 8 hours; R-134a AEL is 1000 ppm; R-22 AEL is 1000 ppm. Treat any measured concentration above 1000 ppm as an evacuation trigger.

An oxygen-deficient atmosphere is below 19.5% O2 by volume; oxygen-enriched is above 23.5%. Confined-space entry requires gas testing for O2, flammability (%LEL), and specific toxics before and during entry.

Recovery cylinder fill rule: never exceed 80% of cylinder water capacity by liquid volume; use a scale and the refrigerant's liquid density (e.g., R-410A approx. 1.06 kg/L at 21 C) to convert.

Refrigerant cylinders must be hydrostatically retested per the cylinder's stamped date (commonly every 5 years for DOT/TC cylinders, 10 years for some low-pressure service cylinders); do not fill an out-of-date cylinder.

Ozone depletion potential (ODP) and global warming potential (GWP) are the two environmental metrics: R-22 ODP 0.055, GWP 1810; R-410A ODP 0, GWP 2088; R-134a ODP 0, GWP 1430; R-32 ODP 0, GWP 675; R-290 (propane) ODP 0, GWP 3.

A2L mildly flammable refrigerants (R-32, R-454B, R-452B) require ignition-source control, room-area/charge limits per the installation standard, and leak-detection or mitigation where the standard requires it; charging and brazing must follow the manufacturer's A2L procedure.

Electrical safe work: lockout/tagout with verified isolation, test-before-touch with a proven meter, and arc-flash PPE category selected from the incident-energy label; capacitors must be discharged and proven dead before touching terminals.

Ladder and fall protection: portable ladders are set at a 4:1 slope (75 degrees) and extend 1 m (3 ft) above the landing; fall arrest is required where a worker can fall 3 m (10 ft) or more in most Canadian jurisdictions.

Manifold gauge sets: blue = low side, red = high side, yellow = service/charging line. Use dedicated gauges for A2L refrigerants; do not cross-contaminate oils between refrigerant classes.

Vacuum measurement: a micron gauge at the pump port reads system pressure; target 500 microns or lower and a standing rise of no more than 200 microns in 10 minutes indicates a dry, tight system.

Torque values matter for flare and seal fittings: over-torquing distorts flares and causes leaks; under-torquing leaks. Use the manufacturer's flare torque table (e.g., 1/4 in approx. 10-12 ft-lb, 3/8 in approx. 25-30 ft-lb).

Brazing requires nitrogen purge at low flow (approx. 1-3 CFM) to prevent internal oxidation (scale); use silfos (15% silver) for copper-to-copper and stay-brite or flux for dissimilar metals.

Leak detection hierarchy: electronic refrigerant detector (heated-diode or infrared) for trace leaks, UV dye for hard-to-reach joints, soap bubbles for confirmation, and pressure/standing vacuum test for gross leaks.

Multimeter basics: measure voltage in parallel, current in series (clamp for AC amps), resistance with power off and component isolated. A clamp meter reads AC amps; a microamp meter reads flame-sensor current.

Recovery equipment: a recovery machine rated for the refrigerant class; recovery cylinders are liquid-vapour (two-valve) and must be labelled with refrigerant type and gross weight; never mix refrigerants in one cylinder.

PPE for service: safety glasses with side shields, nitrile gloves for oil/refrigerant contact, and insulated tools rated 1000 V for electrical work; refrigerant contact causes frostbite, so use gloves and eye protection when opening a charged system.

Ohm's law: V = I x R; power P = V x I = I squared x R = V squared / R. In AC circuits use impedance Z in place of R and account for phase angle.

Series circuits: current is common, voltage divides, total resistance is the sum. Parallel circuits: voltage is common, current divides, total resistance is less than the smallest branch (1/Rt = 1/R1 + 1/R2 + ...).

Single-phase 240 V residential: two 120 V legs 180 degrees apart; L1 to L2 = 240 V, L1 or L2 to neutral = 120 V. Three-phase 208/120 V wye: line-to-line 208 V, line-to-neutral 120 V, phase angle 120 degrees.

Capacitors: run capacitors are measured in microfarads (uF); a failed run capacitor usually reads open or far below rated uF. Start capacitors are higher uF and short-duty; replace with equal or slightly higher uF, never lower voltage rating.

Motor winding checks: measure resistance across start, run, and common terminals; common-to-run plus common-to-start should equal run-to-start. Insulation resistance to ground should be above 1 megohm (often 100+ megohm on good motors).

Semiconductors: a diode drops approx. 0.6-0.7 V forward (silicon); a bridge rectifier converts AC to pulsating DC; a triac or SCR controls AC power by phase angle; a thermistor changes resistance with temperature (PTC rises, NTC falls).

Control transformers step 240/208 V down to 24 V for thermostats and contactors; a shorted 24 V circuit will blow the low-voltage fuse or trip the transformer's internal thermal protector.

Electronic control boards use low-voltage DC logic; test with a meter on the DC scale and confirm 5 V and 12 V rails before condemning a board; check for swollen capacitors and burned traces first.

Contactors and relays: the coil is the control circuit, the contacts are the power circuit. A contactor with pitted or welded contacts causes a compressor to run continuously or not start; check coil voltage and contact resistance.

Overload protection: thermal overloads (heaters or bimetal) protect the compressor against sustained overcurrent; a tripped overload resets automatically or manually depending on type. Check amp draw against nameplate RLA/LRA before resetting repeatedly.

Defrost controls: electromechanical timers use a motor and cam; electronic adaptive defrost boards count compressor run time and door openings. A failed termination thermostat or heater causes no-defrost (iced coil) or continuous defrost (warm box).

Start components: a PTC or current relay assists starting; a hard-start kit (start capacitor plus potential relay) is added when supply voltage sags or the compressor is hard to start. Verify capacitor uF and relay coil before adding a kit.

Thermostats and sensors: a mechanical thermostat uses a bimetal element and anticipator; electronic thermostats use thermistors. Sensor resistance changes with temperature; check the sensor curve against the manufacturer's table, not just continuity.

Pressure switches: high-pressure switch opens on overpressure (condenser airflow, overcharge, non-condensables); low-pressure switch opens on undercharge or low load. Never bypass a safety switch permanently; test the switch and the cause.

Fan and blower motors: PSC motors use a run capacitor; ECM/brushless DC motors have an integrated control module and require a specific signal (PWM or 24 V) to run. Confirm the module's low-voltage signal before replacing the motor.

Grounding and bonding: the equipment grounding conductor provides a fault path; a missing or high-resistance ground causes nuisance trips and shock hazard. Verify ground continuity from the panel to the appliance frame.

The refrigeration cycle: compressor raises pressure and temperature; condenser rejects heat and subcools the liquid; metering device (cap tube, TXV, EEV) drops pressure; evaporator absorbs heat and superheats the vapour; the cycle repeats.

Superheat = evaporator outlet temperature minus evaporating (suction) saturation temperature. Target superheat depends on indoor wet-bulb and outdoor dry-bulb; a fixed-orifice system at design conditions typically runs 8-12 F superheat.

Subcooling = condensing (liquid line) saturation temperature minus liquid line temperature. TXV systems are charged to a target subcooling (commonly 8-12 F); low subcooling with high superheat suggests undercharge.

Saturation temperature is read from a pressure-temperature (PT) chart for the specific refrigerant; never use another refrigerant's chart. R-410A at 118 psig saturates near 40 F; R-134a at 37 psig saturates near 40 F.

Airflow: sensible heat = 1.08 x CFM x temperature difference (F); total heat = 4.5 x CFM x enthalpy difference (Btu/lb). Typical residential airflow is 350-450 CFM per ton of cooling (12,000 Btu/h per ton).

Static pressure: total external static pressure is measured across the blower; a typical residential target is 0.5 in. w.c. or less. High static pressure reduces airflow and capacity and can freeze the evaporator coil.

Compressor types: reciprocating, scroll, and rotary; scroll compressors are common in residential split systems and are direction-sensitive. A compressor that hums and trips on overload may have a locked rotor or a failed start component.

Metering devices: capillary tubes are matched to the system and not adjustable; TXVs maintain constant superheat over a load range; EEVs are stepper-driven and controlled by the board. A restricted metering device causes low suction pressure and high superheat.

Line-set sizing and routing: follow the manufacturer's maximum equivalent length and vertical separation; add refrigerant per the chart for line length beyond the factory charge. Insulate the suction line fully and support it per code.

Evacuation and dehydration: triple-evacuate or use a large pump to reach 500 microns or below; hold a standing vacuum test (rise under 200 microns in 10 minutes) before charging. Moisture in the system forms acids and sludge.

Charging methods: weigh-in for factory-charge systems and for any system with a known line length; use superheat or subcooling targets for field charging when the charge is unknown. Never charge by gauge pressure alone.

Electrical connection: verify supply voltage and phase, tighten terminations to torque, confirm breaker and wire size per nameplate MCA/MOP, and check ground continuity. Record voltage and amp draw at commissioning.

Commissioning records: record ambient and indoor conditions, suction and liquid pressures, superheat, subcooling, static pressure, amp draw, and refrigerant added. These become the baseline for future diagnostics.

Customer handover: explain thermostat operation, filter maintenance interval, and what the warranty covers; provide the model and serial numbers, the refrigerant type and charge, and the service contact. Document the walkthrough.

Permits and code: installation must comply with the local electrical and refrigeration codes and the manufacturer's installation manual; the manual governs clearances, venting, and drain requirements. Keep the manual with the equipment.

Condensate management: slope the drain at least 1/8 in. per foot, install a trap where required, and provide a secondary drain or float switch where the code or manufacturer requires it to prevent water damage.

Start with the complaint and the sequence: verify the symptom, check the power supply and thermostat call, then work from the control circuit to the power circuit. Confirm the call for cool or heat at the board before condemning components.

No-cool diagnosis: confirm compressor and fan operation, then read suction and liquid pressures and superheat/subcooling. Low suction with high superheat suggests undercharge or restriction; high suction with low superheat suggests overcharge or a stuck-open metering device.

Frozen evaporator causes: low airflow (dirty filter, blocked coil, failed blower), low charge, or a restricted metering device. A frozen coil masks the real fault; thaw and re-test before charging.

Electrical diagnosis: measure voltage drop across switches and contacts (a good contact drops near zero); a significant drop indicates resistance. Check amp draw against nameplate RLA; high amps with normal pressures suggests a mechanical or electrical motor fault.

Capacitor and motor tests: measure capacitor uF against the rated value (replace if more than 10% low); test motor windings to ground for insulation breakdown. A motor that hums without starting may have a failed capacitor or open winding.

Refrigerant leak diagnosis: if the system is low, find and repair the leak before recharging. Use electronic detection at joints, Schrader ports, and coil bends; pressure-test with nitrogen and confirm with a standing vacuum.

Control board diagnosis: check for the call input, the output signal, and the board's status LED or fault code. Confirm sensor readings against the manufacturer's table; a board is condemned only after inputs and power are verified.

Documented baseline: compare current readings to the commissioning record. A drift in superheat, subcooling, or amp draw points to a developing fault (charge loss, dirty coil, failing motor) before a hard failure occurs.

Refrigerant recovery: recover to the required vacuum level (commonly 0 psig or a specified micron level per the recovery standard) before opening the system; recover into a dedicated cylinder and record the amount. Never vent refrigerant to atmosphere.

Component replacement: isolate and lock out power, recover refrigerant, purge with nitrogen, and use the manufacturer's replacement part or an approved equivalent. Torque flare and seal fittings to spec and leak-test after reassembly.

Compressor replacement: match the compressor to the system's refrigerant and oil (POE for R-410A and R-32, mineral oil for R-22), replace the filter-drier, and verify the crankcase heater and start components. Add oil only per the manufacturer's chart.

Brazing and soldering: flow nitrogen during brazing, use the correct filler alloy, and pressure-test the joint. After brazing, replace the filter-drier if it was exposed to heat or moisture.

Evacuation after repair: always evacuate to 500 microns or below after opening the system; a system that will not hold vacuum has a leak or moisture. Do not charge until the vacuum test passes.

Electrical repair: replace failed components with the same ratings (voltage, uF, amp); verify wire gauge and terminations. After repair, measure amp draw and voltage at the component and confirm normal operation under load.

Service documentation: record the diagnosis, the parts replaced, the refrigerant recovered and charged, the readings before and after, and the warranty status. This record protects both the technician and the customer.

Post-repair verification: run the system through a full cycle (cool and heat where applicable), confirm pressures, superheat/subcooling, amp draw, and airflow, and check for leaks at every joint touched.

Work order content: customer name and contact, equipment model and serial, complaint, diagnosis, work performed, parts and refrigerant used, readings, and technician signature. This is the legal and warranty record.

Refrigerant records: many jurisdictions require tracking of refrigerant purchased, recovered, and charged, and technician certification. Record the refrigerant type and amount on every service call.

Warranty practice: distinguish manufacturer warranty (parts, sometimes labour) from the contractor's labour warranty; document the installation date and any prior repairs. Do not alter or remove serial tags.

Customer communication: explain the fault in plain language, present repair options with costs, and obtain approval before work beyond the authorized scope. Confirm the customer understands maintenance and safety items.

Professional conduct: arrive on time, protect the customer's property with drop cloths and shoe covers, and leave the work area clean. Follow the employer's safety program and the local code of ethics.

Estimates and invoicing: itemize parts and labour, state taxes and any diagnostic fee, and note the warranty on the invoice. Keep a copy of the signed authorization for the file.

Continuing competence: refrigerant handling certification, electrical licensing where required, and manufacturer training are prerequisites for certain work; keep certificates current and know the scope of your authorization.

Privacy and records: customer information and equipment records are confidential; retain service records for the period required by the employer and the warranty terms, and dispose of them securely.