To avoid changing the composition of the blend, it is important that the refrigerant be charged into the system in the liquid state. An exception to this is when the entire contents of the refrigerant container is charged into the system, Refrigerant cylinders for use with refrigerant blends are equipped with dip tubes so that liquid can be discharged from the cylinder in an upright position. The refrigerant system will require a smaller charge with R-401a or R-401b than with R-12. For most systems, the required charge will be 75% to 90% by weight of the system be initially charged with 70% to 75% by weight of the original R-12 charge. Then, if the system is undercharged, add additional refrigerant in increments of 3% to 5% of the original R-12 charge.
Since the new refrigerant blends are not compatible with the mineral oil lubricants ordinarily used