CAUTION 
A proper vacuum must be drawn on the refrigerant system prior to charging. If this is not done the refrigerant will combine with the moisture in the pipes to form an acid that will eventually cause compressor failure.
FINE TUNING THE SYSTEM CHARGE
2.7.3.2-20ºF Variable Speed Control
The following instructions are for charging systems with condenser fan cycling or variable speed control using R-22 refrigerant.
1.Bleed air from hoses and "break" the system vacuum by supplying R-22 vapor. Supply R-22 vapor until the pressure is raised to about 50 psig. This small holding charge allows the low pressure switch to “make” throughout the pro- cess of fine tuning the system charge
WARNING 
Do not add liquid R-22 refrigerant to the suction side of the system.
2.Start the system and use the microprocessor controller to lower the supply water temperature set-point 3-5°F below actual water temperature. This will ensure the cooling mode stays on during the charging procedure.
CAUTION 
An adequate heat load must be supplied to the unit to ensure a proper charge.
3.Supply R-22 vapor to the suction port until the liquid line sight glass is cleared of all bubbles.
4.After the unit has stabilized, the liquid line sight glass should be clear and the discharge pressure should be a minimum of 200 psig. A superheat reading should be taken 6 inches from the com- pressor, with the temperature-measuring device being well insulated. The superheat should be approximately 10-12 ºF.
5.A sub cooling reading should be taken on the output side of the condenser, with the tempera- ture-measuring device being well insulated. The
sub-cooling temperature should be approximately 10-20 ºF.
NOTE
Under cold climate conditions it is recommended to do the following:
6.Block off the intake air to the condenser with cardboard (or reduce the water glycol flow) until a constant discharge pressure (225-280 psig) can be obtained. This will lower the possibility of overcharging and avoid the occasional bubbles that may appear in the sight glass during fan cycling.
7.Ensure the crankcase heater is operational by checking the amperage.
CAUTION 
Remove the blockage to the air intake of the condenser (or restore the water/glycol flow).
9.Fill out applicable blocks of Warranty Registration and Start-Up Checklist.
2.7.4R407C Refrigerant Charging Procedures
R-407C is a blended refrigerant recognized for being safer for the environment. Refrigerants that are multi- component blends have component parts with different volatilities that result in a change in composition and saturation temperature as evaporation and condensation occur. Typically the composition of R-407C vapor is different than that of R407C liquid within a contained system. The composition of liquid R-407C refrigerant remains relatively constant, however, the refrigerant vapor tends to separate into its component parts even when circulating. When charging a system using blended refrigerants, it is essential that the composition of the refrigerant is maintained. To ensure correct composition, introduce R-407C into the system in liquid form rather than vapor form. Cylinders which are not provided with dip tubes should be inverted to allow only liquid refrigerant to charge the system. Keeping the temperature of the cylinder below 85°F will help to maintain the correct refrigerant composition while the cylinder is emptied.
