FYI 407c evaporator glide is generally said to be 8 degrees F.
The bubble and dew are 11 degrees apart at a normal evaporator pressure. Flash loss will never allow the bubble temperature to be reached in an evaporator.
Average evaporator temperature will be four degrees less than the dew.
Im not sure how many orings are in the system but as mentioned in a post above, they will need to be changed.
Also, I normally start with 90 percent r-22 nameplate charge and adjust as needed.
Since R22 is so expensive now, what does everyone think now about converting the RTAA?
This is an old thread, but is now more relevant than ever. At this point, I still haven't tried a retrofit, but I can see it in the near future. I still haven't heard of anyone else trying it either. Maybe someone will chime in with some experience.
Have wrench-Will travel
RTAA EXV is controlled by the difference of the two temperature sensors mounted on EXV expansion side and suction. There´s no pressure reading, so it will be no problem controlling it with R407C. But one thing I tell you, you´ll have to get the next size of EXV, or try to open the orifice...
i think the same as i did before. not a good idea. fix the leaks and leave it alone. in every case i found (theoretically), R407c costs you more in energy costs. R22 is a fixed, one time cost. the energy used is EVERY time the compressor runs. add in a small leak and with R407c you are most likely recovering and replacing all of the refrigerant (fractionation). with R22...top it off. that is cheaper, too.
Originally Posted by DigtalCracHead
Someday, I hope to be just as brave as Harry Stamper.
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1. Remove all the automation of Trane.
2. Install the new controller, allowing screw compressor control in the continuously variable mode. It will be easier and cheaper than to invent a bicycle with square wheels.
3. Set more powerful fans (condensers power decreases by 12% at the transition 407)
4. Oil, sensors, all for a replacement.
5. Wash all the old oil from the evaporator.
6. Forget it and buy a beer.
Trane doesn't have an official retrofit solution in the States and I've never tried it but there is a set point in the bottom of the configuration menu to select the refrigerant in the machine. The choices are R-22, R-134A, & R404A and the pressure- temperature relationship on the display corresponds with the refrigerant setting. This setting is in the UCP2 style controller factory installed on the 70-120 ton chiller. The larger RTAA's can be retrofitted with this controller also. I can't remember on the older style controller if there is a refrigerant setpoint.