Red Seal Appliance Service Technician flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

AEL for R-410A

The acceptable exposure limit for R-410A is 1000 ppm over an 8-hour period. Concentrations above this trigger evacuation and ventilation, and the space must be tested before re-entry.

Recovery cylinder fill limit

Never fill a recovery cylinder above 80% of its water capacity by liquid volume. Use a scale and the refrigerant liquid density to convert, and never mix refrigerant types in one cylinder.

Oxygen deficiency threshold

An atmosphere below 19.5% oxygen by volume is oxygen-deficient and requires supplied-air respiratory protection and confined-space procedures. Above 23.5% is oxygen-enriched and increases fire risk.

Ladder setup angle

Portable extension ladders are set at a 4:1 slope, about 75 degrees, and extend at least 1 m (3 ft) above the landing. Fall arrest is required where a fall of 3 m or more is possible.

Micron vacuum target

Evacuate to 500 microns or lower, then hold a standing vacuum test: a rise of no more than 200 microns in 10 minutes indicates a dry, leak-free system ready for charging.

Nitrogen purge while brazing

Flow low-pressure nitrogen (about 1-3 CFM) through the system while brazing to prevent internal oxidation. Oxide scale contaminates oil and plugs metering devices and filter-driers.

Manifold gauge colour code

Blue connects to the low side, red to the high side, and yellow to the service or charging line. Use dedicated gauges for A2L refrigerants to avoid cross-contaminating oils.

Ohm's law and power

V equals I times R, and power P equals V times I, or I squared times R, or V squared divided by R. In AC circuits, impedance Z replaces resistance and phase angle must be considered.

Series versus parallel resistance

In series, current is common and resistances add. In parallel, voltage is common and total resistance is less than the smallest branch, calculated as the reciprocal sum of branch reciprocals.

Run capacitor failure test

Measure microfarads against the rated value with the capacitor discharged. Replace when the reading is more than 10% below rated, when it reads open, or when the case is bulged or leaking.

Motor winding resistance check

Measure common-to-run plus common-to-start; the sum should equal run-to-start. Insulation resistance to ground should exceed 1 megohm, with good motors often reading above 100 megohm.

Contactor coil versus contacts

The coil is the low-voltage control circuit and the contacts carry the power circuit. Pitted or welded contacts cause continuous running or failure to start; check coil voltage and contact resistance.

High-pressure switch function

The high-pressure switch opens on overpressure caused by restricted condenser airflow, overcharge, or non-condensables. Never bypass a safety switch permanently; find and correct the cause first.

ECM blower motor signal

An ECM or brushless DC motor has an integrated control module and needs a specific low-voltage signal, often PWM or 24 V, to run. Confirm the signal before condemning the motor.

Superheat definition

Superheat is evaporator outlet temperature minus the evaporating saturation temperature read from the refrigerant's pressure-temperature chart. Fixed-orifice systems at design conditions typically run 8-12 F superheat.

Subcooling definition

Subcooling is condensing 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.

Sensible heat airflow formula

Sensible heat in Btu/h equals 1.08 times CFM times the temperature difference in F. Total heat equals 4.5 times CFM times the enthalpy difference in Btu per pound of dry air.

Airflow per ton

Typical residential cooling airflow is 350 to 450 CFM per ton, where one ton equals 12,000 Btu/h. Low airflow reduces capacity and can freeze the evaporator coil.

Total external static pressure

Total external static pressure is measured across the blower with a manometer. A typical residential target is 0.5 in. w.c. or less; higher readings reduce airflow and capacity.

Weigh-in charging method

Weigh refrigerant into factory-charge systems and any system with a known line length, adding per the manufacturer's chart for line length beyond the factory charge. Never charge by gauge pressure alone.

Commissioning baseline record

Record ambient and indoor conditions, suction and liquid pressures, superheat, subcooling, static pressure, amp draw, and refrigerant added. These readings become the baseline for later diagnostics.

Condensate drain slope

Slope the condensate drain at least 1/8 in. per foot, install a trap where required, and provide a secondary drain or float switch where code or the manufacturer requires it.

Low suction with high superheat

Low suction pressure combined with high superheat points to undercharge or a restricted metering device. High suction with low superheat suggests overcharge or a metering device stuck open.

Frozen evaporator causes

A frozen evaporator results from low airflow such as a dirty filter or failed blower, low refrigerant charge, or a restricted metering device. Thaw the coil and re-test before charging.

Voltage drop across contacts

A good closed contact or switch drops nearly zero volts. A measurable voltage drop under load indicates resistance from pitting, loose terminations, or a failing switch, which must be corrected.

Leak repair before recharge

If a system is low on refrigerant, locate and repair the leak before recharging. Use electronic detection at joints and ports, pressure-test with nitrogen, and confirm with a standing vacuum test.

Recovery before opening system

Recover refrigerant to the required level, commonly 0 psig or a specified micron level, before opening the system. Recover into a dedicated cylinder and record the amount; never vent to atmosphere.

Compressor oil matching

Match the compressor to the system refrigerant and oil: POE for R-410A and R-32, mineral oil for R-22. Replace the filter-drier and add oil only per the manufacturer's chart.

Post-repair verification

After repair, run a full cycle and confirm pressures, superheat, subcooling, amp draw, and airflow. Leak-test every joint touched and record readings before and after the repair.

Work order documentation

A complete work order records customer contact, equipment model and serial, complaint, diagnosis, work performed, parts and refrigerant used, readings, and technician signature. It is the legal and warranty record.

Refrigerant tracking requirement

Many jurisdictions require technicians to be certified and to record refrigerant purchased, recovered, and charged. Record the refrigerant type and amount on every service call.

Warranty versus labour coverage

Manufacturer warranty typically covers parts and sometimes labour; the contractor's labour warranty is separate. Document the installation date and prior repairs, and never remove or alter serial tags.