System Troubleshooting & Safety Flashcards

When evacuating a refrigeration system before charging, what vacuum level is considered acceptable under industry best practices in Canada?

Answer: 500 microns (500 µm Hg) or lower, verified by a micron gauge with the vacuum pump isolated

Industry best practice and many manufacturers require the system to reach 500 microns (µm Hg) or lower, confirmed with a micron gauge after the vacuum pump is isolated, to ensure adequate moisture and non-condensable removal before charging.

What symptom would a restricted liquid line filter-drier produce in a refrigeration system?

Answer: Low suction pressure, high superheat, subcooling drop across the drier, and possibly a cold or frosted drier body

A restricted filter-drier creates a pressure drop across it, starving the expansion device of liquid — the result is low suction pressure, high superheat, a measurable subcooling temperature drop across the drier, and possibly frost on the drier body where pressure drops sharply.

What is the first action a technician should take upon arriving at a site where ammonia refrigerant is suspected to be leaking?

Answer: Evacuate the area, call emergency services if the leak is significant, don appropriate PPE (SCBA for large leaks), and follow the facility's emergency response plan before re-entering

Ammonia is toxic at low concentrations and immediately dangerous to life and health (IDLH) at 300 ppm; the first priority is personnel safety — evacuate, notify emergency services for large releases, and ensure proper respiratory protection (SCBA) before entering a contaminated area.

What is the purpose of a nitrogen purge when brazing refrigerant lines?

Answer: To displace oxygen inside the pipe during brazing, preventing oxide scale formation inside the copper tube that would contaminate the refrigerant system

Flowing dry nitrogen through the tubing during brazing displaces oxygen inside the pipe, preventing the formation of copper oxide scale (cupric oxide) that would otherwise flake off and contaminate the compressor valves and expansion devices.

A system has been operating normally for a long time but now shows gradually rising discharge pressure and head pressure over several weeks. The condenser coil is clean. What is a likely cause?

Answer: Non-condensable gases (air or nitrogen) accumulating in the system from a low-side leak or improper service procedure

Non-condensable gases accumulate at the top of the condenser and raise head pressure over time; if the source is a low-side leak (suction pressure below atmospheric), air can be drawn in, gradually building up non-condensables in the system.

Under Canadian OHS regulations, what is required before a technician enters a confined space that may contain refrigerant vapour?

Answer: A confined space entry permit, atmospheric testing for oxygen level, flammable gases, and toxic contaminants, and a standby person outside the space

Provincial OHS regulations across Canada require a formal confined space entry program including written permits, atmospheric testing (O2, flammable gas, toxic substances including refrigerants), and a trained attendant outside before any worker enters a confined space.