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Hi Everyone,
First of all I'm new hear so HELLO
I have to convert an r22 cold room fridge cold room, i perfume to 134a
what is the best way i have been told to calculate the volume of the box and then select a suitable condensing unit and keep the existing evaporator is this correct ?
thanks
You will need a larger condensing unit if you want to keep the evaporator.
A new TXV and all liquid line components.
A wash of the old piping and evaporator from mineral oil residue.
Condensing unit will be about 30% bigger.
On the other hand you can replace r22 to 422d and keep the unit running, replacing only drier.
Another option would be R407F in the existing condensing unit, a change to poe oil would be needed, also o rings or component replacement, i believe danfoss are making tev's for R407F now too. The main benefit is the low 1850 GWP of R407F compared to many drop ins in light of the 2500 GWP threshold the nutters in charge seem to see as a cut off for future viable refrigerants, though as you know R134a has an even lower GWP at 1430.
And similar to most of R400-blend - R407F have glide a 5 degree C from bubble do dew - or if 25% of mass expand to vapour after TXV to cool down liquid itself - you have 4 degree C glide left in evaporator (0/45 degree C working space and 7 degree C super cool on liquid)
Most fit i pressure and capacity for single component refrigerant (and higher theoretical COP than all of R400-blends) to replace R22 is using R1270 (propylene) and not need change oil, but I think charge-load is to big here, and also flammable and system should designed for R1270 from beginning or rebuild for this refrigerant to remove all sparking open relay etc.
It is not viable to upgrade to one of the Flammable refrigerants due to the safety requirements , so the best option is either R407F or R407A . As MS states Danfoss now supply thermostatic expansion valves for R407F and R407A. These valves have a power element charge that is suitable for use on both R407F and R407A, or you could also upgrade the plant by fitting a more energy efficient Electronic Expansion valve where the controller can be programmed for up to 37 different refrigerant types including the 2 mentioned. The supermarkets are now using these 2 gases as replacements for R22 and R404A