R-410A flashcards

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

R-410A composition

A near-azeotropic blend of 50% R-32 (difluoromethane) and 50% R-125 (pentafluoroethane) by mass, with a temperature glide of only about 0.1 to 0.2 K.

R-410A atmospheric boiling point

At one atmosphere R-410A boils at about -51.4 °C (-60.6 °F), so at any given temperature its pressure is far higher than that of R-22.

R-410A pressure at 38 °C

Saturation pressure at 38 °C (100 °F) is roughly 317 psig (2185 kPa gauge), about 60% higher than R-22 under the same conditions, which drives component pressure ratings.

R-410A ASHRAE A1 rating

R-410A is class A1: low toxicity and no flame propagation in standard tests. It is still an asphyxiant, and liquid contact can cause frostbite or eye injury.

POE oil moisture absorption

Polyolester lubricant used with R-410A is highly hygroscopic; it absorbs moisture in minutes, forming acids and sludge that damage compressor windings and block small passages.

Section 608 certification

US EPA certification under Section 608 of the Clean Air Act is required before a technician may service, maintain, repair, or dispose of equipment containing ozone-depleting refrigerants or their HFC substitutes.

Venting prohibition

Knowingly venting CFC, HCFC, or HFC refrigerant to the atmosphere is illegal; the refrigerant must be recovered and then recycled, reclaimed, or destroyed.

Leak rate thresholds

EPA thresholds that trigger mandatory repair are 10% per year for comfort cooling, 20% for commercial refrigeration, and 30% for industrial process refrigeration appliances.

Recordkeeping requirement

Refrigerant purchase records, service logs, and leak repair verification documents must be kept for at least three years and made available to EPA on request.

Four main cycle components

The compressor raises pressure and temperature, the condenser rejects heat and condenses the vapor, the metering device drops pressure, and the evaporator absorbs heat and boils the refrigerant.

Superheat definition

Superheat equals the actual suction line temperature minus the saturated suction temperature at the measured pressure; it confirms that only vapor leaves the evaporator.

Subcooling definition

Subcooling equals the saturated condensing temperature at the measured head pressure minus the liquid line temperature; it confirms solid liquid reaches the metering device.

Compression ratio formula

Compression ratio is absolute discharge pressure divided by absolute suction pressure, expressed in psia or kPa absolute; gauge readings must be converted before dividing.

Nitrogen purge while brazing

Dry nitrogen must flow through the tubing at about 1 to 2 SCFH during brazing so internal copper oxide scale does not form and later clog driers and valves.

Micron evacuation target

A tight system is evacuated to 500 microns (0.5 mm Hg) or lower; one atmosphere equals 760 mm Hg, or 760,000 microns.

Standing vacuum decay test

After reaching 500 microns, isolate the pump and hold 10 to 15 minutes; a rise above roughly 1000 microns indicates a leak, moisture, or outgassing.

Triple evacuation procedure

Evacuate, break the vacuum with dry nitrogen, and repeat three times; the nitrogen sweeps moisture out when the vacuum will not hold or the system was opened.

Pressure testing safety

Dry nitrogen is the only acceptable test gas; oxygen or air mixed with refrigerant oil can detonate, and acetylene must never be used for pressure testing.

Weigh-in charging

The most accurate method is charging liquid refrigerant by weight on a scale, using the nameplate charge plus any adjustment for line length or added components.

Charging by subcooling

Systems with a TXV are charged to the manufacturer's target subcooling, typically 8 to 12 °F (4 to 7 K) at the liquid line, at design indoor and outdoor conditions.

Charging by superheat

Fixed-orifice systems are charged to a target superheat taken from the manufacturer's chart, using indoor wet-bulb and outdoor dry-bulb temperatures.

Liquid-only R-410A charging

R-410A must always be charged as a liquid; drawing vapor from the cylinder fractionates the blend and changes the R-32 to R-125 ratio and the system's performance.

High head pressure causes

Dirty or blocked condenser coils, overcharge, non-condensable air, high ambient temperature, and a failed condenser fan all raise discharge pressure above normal.

Recovery cylinder 80% limit

A recovery cylinder may never be filled above 80% of its capacity by weight; liquid expansion at higher temperatures can rupture a full cylinder, so a scale must be used.

Recovery recycling reclamation

Recovery is removal of refrigerant into a cylinder; recycling is on-site cleaning with oil separation and filter-driers; reclamation is off-site reprocessing to AHRI 700 purity.

AHRI 700 purity standard

AHRI Standard 700 sets the purity and composition limits for reclaimed refrigerant, and only an EPA-certified reclaimer with laboratory analysis can certify it.

Never mix refrigerants

Mixing different refrigerants in one cylinder creates an unidentifiable blend that cannot be reclaimed and may not be reused; keep each refrigerant in its own cylinder.

Recovery cylinder identification

DOT recovery cylinders are usually gray with a yellow top and must carry current hydrostatic test dates; virgin R-410A cylinders are rose colored and are never used for recovery.

AIM Act phasedown schedule

The US AIM Act caps HFC production and consumption, stepping down 10% in 2022, 40% in 2023, 70% in 2029, 80% in 2034, and 85% by 2036.

A2L classification

A2L refrigerants have low toxicity and mild flammability with burning velocity at or below 10 cm/s, requiring charge limits, leak detection, and ignition-source control.

R-454B composition and GWP

R-454B is a near-azeotropic blend of about 68.9% R-32 and 31.1% R-1234yf with a 100-year GWP near 466, roughly one-fifth that of R-410A.

R-410A GWP value

R-410A has a 100-year GWP of 2088 (IPCC AR4) and zero ozone depletion potential; its high GWP is the reason for the transition to lower-GWP alternatives.