Metering Devices and System Charging

Metering devices and refrigerant charging, followed through a second-year apprentice at an HVAC-R contractor in Kitchener: what every metering device does; capillary tubes and fixed orifices; thermostatic expansion valves, their bulbs, equalizers, setup and troubleshooting; electronic expansion valves and their sensors; automatic expansion valves and float metering; superheat and subcooling diagnostics; evacuation and decay testing; charging by weight, superheat, subcooling and manufacturer charts; blends with glide, low ambient and inverter systems; and safe charging of A2L refrigerants under CSA B52.

RAC-220 12 lessons · 3 h 25 min ▶ Video lessons coming soon

Offered by HSM University · Refrigeration and Air Conditioning

This is the Canadian version of this course. See the American version.

What you'll learn

Explain the two jobs of every metering device, calculate how subcooling reduces flash gas, and recognize starved, flooded and correctly fed evaporators
Describe how capillary tubes and fixed orifices meter, match pistons and capillary tubes to the system, and diagnose restrictions in critical-charge systems
Explain the force balance, bulb charges, equalizers and port designs of thermostatic expansion valves and distinguish static, opening and operating superheat
Install TXVs and mount their bulbs correctly, measure operating superheat at the bulb, and diagnose hunting, overfeeding and starving before adjusting a valve
Describe stepper and pulse-width-modulated electronic expansion valves and their controllers, and check coils, sensors and live data to separate valve, board and charge faults
Explain how automatic expansion valves and float valves meter refrigerant and judge flooded evaporators by level and approach temperature
Take a complete set of readings at stable conditions and use superheat, subcooling, pressures and temperature splits to identify common charge and component faults
Evacuate systems with correct tools and procedures, interpret decay tests to distinguish leaks from moisture, and maintain vacuum pumps
Charge systems by weight with line set adjustment and verify them by target superheat, target subcooling or the manufacturer's charts
Charge zeotropic blends correctly using dew and bubble points, apply low ambient charging limits and head pressure control charge, and follow manufacturers' methods for inverter systems
Apply A2L safety classes, codes and charge limits, use A2L-rated tools and cylinders, and charge, label and commission A2L systems with refrigerant detection
Apply a systematic method to charge-related complaints, repair causes before charging, and keep complete records of readings, repairs and refrigerant amounts

Course content

12 lessons · 3 h 25 min total · final exam

1 The metering device's job 18 min · quiz
2 Capillary tubes and fixed orifices 17 min · quiz
3 Thermostatic expansion valves 18 min · quiz
4 TXV setup, bulb placement and troubleshooting 17 min · quiz
5 Electronic expansion valves 17 min · quiz
6 Automatic expansion valves and float metering 17 min · quiz
7 Superheat and subcooling diagnostics 17 min · quiz
8 Evacuation and dehydration 17 min · quiz
9 Charging methods: weight, superheat and subcooling 17 min · quiz
10 Charging refrigerant blends, low ambient and inverter systems 16 min · quiz
11 A2L refrigerants: safe charging and service 17 min · quiz
12 Charge troubleshooting, documentation and the capstone 17 min · quiz
E Final exam 20 questions

Requirements

RAC-210 Compressors, Condensers and Evaporators

Recommended background. You can start any course at any time.