Refrigerent substitution

IIRC, R134A is both somewhat less dense than R-12, and it boils at a higher temperature per a certain pressure.

In a CCOT system, that would normally only require reducing the size of the oriface tube, and _maybe_ reducing the charge so as not to cause a hydrostatic block on the liquid side. In a thermostatic expansion valve system, you might not have to do anything.

In a capillary tube system, it would require reducing the charge both to avoid hydro-lock, and to establish a lower pressure on the evaporator side.

LLoyd