R-170 (ethane) PT Chart and Refrigerant Profile

Where you will find R-170

R-170 is ethane, a pure hydrocarbon used where temperatures go far below anything a single-stage system reaches. BITZER lists it for cooling products below about -58°F (-50°C), with an application range of -58°F to -139°F (-50 to -95°C). That means the low stage of cascade systems and ultra-low-temperature freezers.

BITZER names it as an alternative to the HFC low-stage refrigerants R-23, R-508A and R-508B, and to the older R-13 and R-503. BITZER also says to use it only where safety regulations allow an A3 refrigerant. In the US, EPA’s SNAP program listed ethane as acceptable with use conditions in very low temperature refrigeration on Apr 10 2015.

Identify it from the nameplate and the flammable-refrigerant markings EPA requires (below). There is no legacy cylinder color for R-170 in AHRI Guideline N-2017. Its containers follow the current scheme: light green-gray with a red band on the shoulder or top for flammables.

Charging R-170

R-170 is a single-component refrigerant: no glide, one PT column, vapor or liquid charging. No manufacturer charging procedure was found. Charge by weight to the nameplate. EPA’s use conditions limit the charge in listed equipment (see below), so a scale reading in grams or ounces matters more than a gauge reading.

Pressures depend on where you are on the curve. On this site’s table ethane reads 3.6 psig at -120°F and 16.6 psig at -100°F. Toward room temperature the curve climbs steeply: 370.2 psig at 40°F. The critical point is 89.9°F, so the chart stops at 87°F. A stopped circuit sitting in a warm room can be above the critical temperature, where its pressure is not a chart value. Never assume an idle low stage is at low pressure, and check the rating of gauges, hoses and recovery cylinders before connecting.

For superheat on the low stage, convert suction pressure to saturation temperature with the PT calculator or the superheat calculator. The pressure converter handles psia and kPa.

Oil and compatibility

BITZER lists PAO, mineral oil and POE for R-170, with alkylbenzene only “with limitations”. It adds that “R170 is also well soluble with conventional oils, but an adaptation to the temperature will be necessary”, meaning the oil must suit very low evaporating temperatures. Linde lists mineral oil, AB and POE. The compressor maker’s approval decides; see the refrigerant oil types guide.

Safety, handling and recovery

R-170 is A3 under ASHRAE 34: lower toxicity, highly flammable. The flammability safety classes page explains the difference from A2L. Work with ventilation, keep ignition sources away, and never braze on a circuit that still holds refrigerant.

EPA’s 2015 listing for very low temperature refrigeration sets these use conditions:

• New equipment only, designed for the refrigerant. Ethane may not be used to retrofit existing equipment.
• Charge size no more than 150 g (5.29 oz).
• Equipment must meet Supplement SB to the 10th edition of UL 471.
• Red PMS #185 markings on pipes, hoses and other devices carrying refrigerant, plus permanent “DANGER - Risk of Fire or Explosion” warning labels.

EPA’s SNAP page refers back to the rule for the full conditions, so check it before working on such equipment.

For Section 608, ethane is a very-high-pressure refrigerant: its critical temperature is below 104°F (40 CFR 82.152). Type II or Universal certification covers it.

The venting rules are unusual. 40 CFR 82.154(a)(1)(vii) exempts “Ethane (R-170) in very low temperature refrigeration equipment and equipment for non-mechanical heat transfer” from the venting prohibition. Hydrocarbons are also exempt in industrial process refrigeration that processes hydrocarbons. Outside those end uses ethane is a non-exempt substitute: no venting, recovery to 0 in Hg for very-high-pressure appliances, and sales restricted to certified technicians since Jan 1 2018. Where you recover a flammable refrigerant, the recovery machine must be certified for flammables (40 CFR 82.158 Appendix B4); see recovery machine compatibility.

Status and replacements

Ethane is not an ozone-depleting substance and not an AIM Act regulated HFC. The phasedown and Technology Transitions GWP limits do not apply to it; EPA’s 40 CFR 84.64 value is 5.5. Its US use is set by SNAP: acceptable with use conditions in very low temperature refrigeration and non-mechanical heat transfer.

That makes it a low-GWP path for small ultra-low equipment that would otherwise use R-23 or R-508B, both high-GWP refrigerants. Compare it with propane, R-290, which shares the A3 handling rules but serves much warmer applications.

Common questions

Is R-170 the same as ethane?

Yes. R-170 is the ASHRAE number for ethane (CH3CH3). Linde lists it simply as Ethane, with no brand name.

R-170 vs R-290?

Both are A3 hydrocarbons. Ethane boils far lower (see the at-a-glance table) and is used in very-low-temperature stages; propane is used in commercial and household refrigeration and room AC.