Oklahoma Refrigeration Contractor

ACR tubing is designated by its actual outside diameter, while copper water tubing nominal size equals the OD minus 1/8″.

Galvanized pipe is treated with a zinc anticorrosion material and used primarily in water systems to prevent rust, while black pipe is usually less expensive and used for gas lines and applications that do not carry water.

Both route compressor discharge gas, but the defrost valve delivers large quantities of hot gas to the evaporator to rapidly melt frost while the bypass valve meters small amounts to prevent compressor damage under low-load conditions.

A motor starter is like a contactor but adds built-in overload protection to prevent motor burnout or overheating; both can be rebuilt by replacing burned contacts or a shorted coil.

A current relay's coil is wired in series with the run winding and has normally open contacts, while a potential relay's coil is wired in parallel with the start winding and has normally closed contacts (so the start components are in the circuit immediately, avoiding the contact arcing common with current relays).

EPA regulations prohibit a change of ownership of recycled refrigerant; before refrigerant can change owners it must be reclaimed to AHRI Standard 700 purity, verified by chemical analysis.

AHRI 740 is the certification label standard for recovery/recycling machines (recovery rate and vacuum capability), while AHRI 700 is the purity specification for reclaimed refrigerant.

Type II covers high-pressure and very high-pressure appliances (commercial refrigeration such as an R-404A walk-in, residential/commercial A/C, non-low-pressure chillers, transport refrigeration), Type III covers low-pressure appliances such as an R-123 centrifugal chiller, and small appliances of 5 lb or less require Type I or Universal.

A single screw compressor uses one main rotor meshing with two star-shaped rotors driven by the main rotor, though the basic operating principles are the same as other screw compressors.

Screw compressor helical rotors produce continuous, steady pressure with very little vibration, unlike the pulsating pumping pressure of a reciprocating compressor.

Eccentric-type rods have a solid ring (usually cast-iron bearing surface) that must be mounted before the crankshaft and eccentric are assembled, whereas crank throw-type crankshafts use a split lower end/end cap.

A range adjustment moves both cut-in and cut-out equally in the same direction (differential unchanged), while a differential adjustment changes the spread — on a low-pressure motor control the differential screw turned clockwise raises only the cut-out pressure, and a combination differential adjustment moves cut-in and cut-out equally in opposite directions to keep the same average temperature with longer run times.

A liquid line restriction gives low suction pressure, low head pressure, high superheat and normal subcooling (with bubbles in the sight glass and a temperature drop at the restriction), while an inefficient compressor gives high suction pressure with low head pressure.

Halide torches and electronic detectors react to the refrigerant chemicals used as an expander in urethane foam and give false positives, so the bubble test is most reliable around urethane insulation; ultrasonic detectors sense escaping vapor sound and work with all refrigerant types.