R404a Oil Return

[dallan]

To expand on a section of the oil return problem thread.

Could it be argued that it would benefit the system if R290 was added as standard to all R404a systems to aid oil return.

My main querys are would this eliminate the need for oil separators and simplify the system and what 290 to 404a ratio should be used (does everyone just add a little and see how it goes?) keeping in mind the regs for HC gases.

[Gary Collins]

Please explain why you need to add R-290 to bring back oil. I have designed many R-404A system and retrofitted HCFC 502 systems to R-404A with suction temps to -40F and I have never had the requirement to add a HC solvent to bring the POE back. With the right suction gas velocities and line slope it should'nt be problem