R404A TX valve used on an R22 system... What could go wrong?

[The Red Krawler]

G'day,

I recently found that a medium temp system that is on R22 has had an R404A TX valve fitted to it. I noticed because the part code used was TES2 (Danfoss R404A TE2 valve) instead of a TEX2 (Danfoss R22 TE2 valve).

Does anyone know what the impact of this would be?

My quick calculation is that if the system gets to -5C SST the bulb will be reading 65psig (R404A) and the valve outlet will be seeing 46psig (R22) which will have the effect of the valve closing significantly more than it should and thus starving the evaporator.

Does that sound about right? The higher bulb pressure will "beat" the spring pressure much more readily and result in less refrigerant and thus higher superheat.

The recommendation will be to change to the correct valve, but I believe the unit is operating just fine so I suspect it may not go ahead. The bigger concern will be if I've got this arse about and the valve will actually OPEN more, risking liquid flood back....


EDIT: Actually, I think I do have it arse about... 5K superheat should see a -5C SST give +0C on the outlet (57.5psig R22) but instead it will be reading 74psig (0C R404A) and thus try to open the valve further.