Refrigerant RS-51 R470B cylinder

RS-51 (R470B)

Refrigerant RS-51 R470B cylinder

ComStar International's RS-51 Is the LOWEST GWP, NON-FLAMMABLE Retrofit Replacement for R404A and R507

ComStar International Inc.’s RS-51, with the ASHRAE designation of R470B, is new to the U.S. market. RS-51 (R470B) is the lowest GWP at 717 retrofit refrigerant to replace R404a and R507 in EXISTING in-place R404a and R507 systems.

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RS-51 (R470B)

RS-51 (R470B) is EPA SNAP-approved and A-1 ASHRAE certified as non-flammable and non-toxic. This unique refrigerant provides exceptional cooling properties and can operate with existing polyol ester (POE) oils present in R404A and R507 systems.

RS-51 (R470B) is an HFO (HydroFluoroOlefins) blend, which is the environmentally friendly alternative to the commonly used HFC blends in other refrigerants. RS-51 can be used with the same tools, test instruments, and recovery machines as R404A and R507.

RS-51 (R470B) was initially invented for the European market due to their stricter GWP (Global Warming Potential) reduction regulations and financial incentives for using low-GWP refrigerants. Now, ComStar is introducing RS-51 (470B) to the U.S. market in response to state and federal legislation that is designed to phase down high-GWP refrigerants, such as R404A and R507. These refrigerants have a GWP of 3943 and 3985 respectively (AR5).

RS-51 (R470B) was formulated to be safely compatible with R404A and R507 compressors, system components, and oils. RS-51 also offers similar performance to R404A and R507, but with a lower discharge pressure than R448A and R449A. These facts make RS-51 (R470B) the perfect replacement choice.

Retrofit Guidelines

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Ensure the right equipment is available, such as: recovery unit and cylinders, container for recovered lubricant, vacuum pump, weighing scales, replacement drier, etc.


Before removing the R404A or R507A, operate the unit under standard operating conditions and record the pressures, temperatures and any other relevant measurable data to establish unit performance.


Recover and weigh the R404A or R507A from the unit. The weight should be within the range specified by equipment manufacturer.


Replace the filter/drier and evacuate the system.


As in the case of R404A and R507, RS-51 should be used with a polyol ester lubricant.


Before operating the unit, charge the unit with liquid RS-51. The weight added at this stage should be approximately 10% lower than the R404A or R507 charge specified by the equipment manufacturer.

Operate the unit under conditions similar to those used in Step 2, closely watching the liquid line sight glass, the compressor oil level sight glass and the suction superheat.


If the system has an electronic expansive device, select the parameters applicable to R134a. Existing TXVs should be replaced with an R134a valve of similar capacity to the existing valve or modified by replacing the element with an R134a power element of similar temperature range.


Clearly label the system to show it contains R470B (RS-51).


Check system thoroughly for leaks.


Remove all R404A or R507A labels and clearly label system RS-51 (R470B).



Given the growing momentum to phase down high GWP HFC refrigerants at the State and Federal level, you may soon be looking for the lowest-GWP alternatives that will satisfy your refrigeration needs. ComStar is the smart choice.