DuPont publishes R404A retrofit guide
29th October 2014
USA: DuPont has produced a must-read document for anyone considering converting an R404A or R507 system to its new alternative XP40.
With a European service ban on R404/507 systems being introduced in 2020, and with high GWP refrigerants coming under increasing pressure elsewhere, there is expected to be huge interest in lower GWP “drop-in” alternatives.
Although the conversion procedure is far from onerous, there are precautions that need to be taken and safety issues to be addressed. This is where DuPont’s Retrofit Guidelines for Stationary Refrigeration is invaluable for anyone considering converting to XP40.
Also known as R449A, DuPont’s branded Opteon XP40 was initially developed as DR33. Specifically designed as a substitute for R404A and R507, it is a blend of R32 (24.3%), R125 (24.7%), R1234yf (25.3%) and R134a (25.7%) with a GWP of 1397. Non-flammable, it has been assigned an A1 safety classification under the ASHRAE standard.
Seek advice
Although XP40 is designed specifically to replace R404A and R507 there are some differences and one of the main pieces of advice when retrofitting is to consult the component manufacturers, particularly the compressor manufacturer but also, if appropriate, the controls manufacturer.
In basic terms, XP40 will work quite happily with the existing POE lubricant but the new gas has a slightly higher discharge temperature of between 10-20K.
According to DuPont, overall system performance will be similar but compressor suction and discharge pressures will differ from R404A/R507 and it may be necessary to adjust set points and cutouts to avoid exceeding the operating limits of the compressor.
Replacement of the expansion device should not be necessary but XP40 has a lower mass flow rate of around 20-25% than R404A, so some adjustment may be needed in order to reset the superheat following conversion.
With XP40’s lower mass flow rates and density, it is also recommended that the existing refrigerant line sizing is checked to verify that the system pressure drops and line velocities are acceptable.
Due to the differences in suction pressure between XP40 and R404A, it may be necessary to reset pressure regulators and pressure cutouts. The discharge pressure of XP40 is slightly lower than R404A and may require slight adjustments to condenser fans and head pressure controls.
As well as a number of other important recommendations, the document also provides a step-by-step guide to retrofitting a system, a retrofit check-list and pressure/temperature data for XP40.
Retrofit Guidelines for Stationary Refrigeration, Converting R-404A/R-507 Systems to Opteon XP40 (R-449A) Refrigerant can be downloaded here.
