21
Charging the Master Controller 2.0 Refrigeration System
Note: If you are a first time installer of a Master Controller 2.0 system,
please call Master-Bilt for on-phone training.
Since the system is designed with free floating head control, the head pressure control valve is not installed in
this type of system. Therefore, the compressor operates at its highest EER value.
During initial pull down, after primary charge while the system is running, a large evaporator superheat is
built up. The electric expansion valve is then open all the way. If the system is charged full sight glass during
this period, the system is already overcharged.
Note: The liquid line size is determined by conventional piping practices
for air and electric defrost. For reverse cycle defrost, the liquid line must
be selected by choosing the liquid line one nominal step larger than the
conventional approach. For example: for an evaporating temperature =
-20ºF, refrigerant R-404A, and a capacity of 20,000 Btuh, the conventional
tables will suggest a liquid line size of ½” OD. When utilizing the reverse
cycle feature of the Master Controller, the liquid line size should be 5/8”
OD. When utilizing the electric or air defrost scheme, there is no need to
make the line larger.
All suction lines may be chosen by conventional practices. Please note
the “stubs” at both the evaporator and condensing unit do no
necessarily mean that this is the correct size for your application.
Calculation of estimated amount of working refrigerant:
The amount of working refrigerant can be estimated by the following formula:
Tons of cooling capacity x 4.5 LBS/Ton + Full Liquid Line Charge between Evaporator and Condenisng
Unit
For example, a system of 12,000 BTUH @ -20F suction, 50 ft 1/2” liquid line run, R404A, 100F Liquid,
the working amount of refrigerant is: 1 x 4.5 + 6.5 x 50/100 = 7.75 LBS R404A. The actual charge should be
approximately this working amount of refrigerant.
Weight of Refrigerant in LBS per 100 ft of Liquid Line:
The recommended charging procedures are:
Liquid Line
Size, Inch
Refrigerant Lbs of Refrigerant
3/8 R22
R404A
4.0
3.5
1 /2 R22
R404A
7.5
6.5
5/8 R22
R404A
12.0
10.5
7/8 R22
R404A
24.5
21.0
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