ClimaCool UCR 30, 50 and 70 tons Manual - Manual (Page 26)

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this must be taken into consideration. This is necessary
since as the compressor unloads, the condenser’s capacity
increases and additional fl ooding is required. Using the same
roof mounted remote condenser as in the earlier example
(40°F evaporator and minus 20°F minimum ambient), a multiplier of .79 is shown in Table 2. And since we have hot
gas bypass (50%), this .79 is used to enter Table 3 to fi nd
a multiplier of .91. This fi nal multiplier is applied to the 119
pounds calculated earlier to arrive at the fi nal extra charge
requirement: 119 x .91 = 108 pounds. This is added to the
normal system charge to arrive at a total system charge.
3/8" 1/2" 5/8" 0.875 1.125 1.375
3/8" 1/2" 5/8" (0.016) (0.017) (0.018) (0.045) (0.05) (0.055)
-40 0.053 0.098 0.157 0.278 0.474 0.722
-20 0.052 0.095 0.152 0.270 0.460 0.701
0 0.050 0.092 0.147 0.262 0.446 0.679
20 0.2 0.25 0.3 0.048 0.089 0.142 0.253 0.431 0.656
40 0.046 0.086 0.137 0.243 0.414 0.631
60 0.044 0.081 0.129 0.229 0.391 0.595
70 0.043 0.080 0.128 0.227 0.387 0.589
R-410A
Refrigerant Tubing O.D. and Wall Thickness (Inches)
Density Factor - Pounds Per Foot Of Tubing
Equivalent Length Of Tubing for
Each Return Bend
Minimum
Ambient
o F
Table 1
Table 2 Table 3
Refrigerant Charging Procedures for Head
Pressure Control Valve
Once the amount of extra refrigerant charge is calculated,
care must be taken in charging the system to insure the
proper total amount of refrigerant getting into the system.
This is especially true if the ambient temperature is
below 70°F and the liquid drain valve (LAC) is throttling
the refrigerant fl ow from the condenser. A step by step
procedure is given below for the two possible situations
that can exist. And depending on the ambient temperature
at the time the system is charged, each should be carefully
followed to insure proper system operation in both summer
and winter. In either case, a liquid seal must be established
in the receiver before the system can start to function
correctly. NOTE: While charging any system with head pressure
control, the outdoor ambient temperature must be known.
And if the system has compressor unloaders, it is important
to know if they are functioning during the charging
procedure. To keep this procedure as simple as possible,
it is recommended that the unloaders be locked out
(compressor fully loaded) during charging.