Superheat and Subcooling

[wambat]

You use sub cooling for TXV and superheat for restrictors/cap tubes and these have a critical charge because they are not very flexable with quick changing loads and therefor are prone toslugging if over charged

[GXMPLX]

You use sub cooling for TXV and superheat for restrictors/cap tubes and these have a critical charge because they are not very flexable with quick changing loads and therefor are prone toslugging if over charged

No, you have to use both to make sure the cap is fed right and simultaneously measure superheat.

You cannot use superheat only.

Anyway I have never seen a successful field charge of these systems.

They need extensive study of charge/load behaviour and for this reason all manufactures indicate amount to charge.

Usually system manufacturers use compressor manufacturer's data on the amount of refrigerant in the crankcase that does not produce flooded start problems because the refrigerant will usually be in the compressor on startup.