Always charge less than the original R-22 charge. Charge 90% of the original R-22 charge, let the system run for twenty minutes, then add refrigerant, if needed. The flow rate of Forane® 427A is within 8% of R-22. Rarely will an adjustment of the expansion device be needed, in most systems. Large systems running EEVs will need to be programmed for the P/T characteristics of R-427A.
Pressure Temperature (P/T) Chart: All refrigerants have a respective P/T chart. Technicians can download the Forane® PT App (found in iTunes and GooglePlay), containing all Forane refrigerants (see QR codes below). Blended gases have two columns: Vapor and liquid. Use the vapor column for calculating superheat and the liquid column for subcooling. Use subcooling for systems utilizing a TXV.
Charging to sight glass: Unlike R-22, which is a single component refrigerant, R-427A is blended from four component refrigerants: R-32, R-125, R-143a, and R-134a. Each component has a different boiling point, which equates to a 9o glide, when combined in ratios specific to R-427A. Seeing bubbles in a sight glass might not be indicative of a low charge, rather it could be a consequence of the glide. Therefore, charging by superheat and subcooling is the only way to attain the optimal charge.
“Topping off”: Forane® 427A refrigerant is a near-azeotrope blend and could fractionate. The rate of fractionation is dependent of several factors: Running vs. dormant and/or liquid vs. gas. Leaks will fractionate at different rates. If the system leaked out more than half of its charge, Arkema suggests you recover the remaining gas and charge the system with new liquid Forane® 427A. The consequences of fractionation could be less than optimal performance, and the actual P/T readings will not match the P/T Chart.
Mixing refrigerants with R-22: A technician is not supposed to mix refrigerants for three reasons.
- EPA 608 prohibits mixing refrigerants in the field.
- The original R-22 will be contaminated with the added refrigerant.
- The P/T readings may not match either P/T chart.
There are no use restrictions on R-22 in the USA. The phase down of R-22 production ends in 2020, however usage can continue until the R-22 supply is completely exhausted. Some systems might benefit by continuing to operate on R-22. Flooded evaporators and recirculation systems will be difficult to retrofit to a blended refrigerant. Arkema recommends continuing to use R-22 in these applications.