FloAire Modular Packaged Unit - Manual (Page 12)

12
98°F – 83.5°F = 14.5°F of subcooling
This should be compared to the condenser nameplate
subcooling, which in this case is 14°F as shown to the
right.
As a reminder, to increase subcooling, add refrigerant charge and to decrease subcooling, remove
refrigerant charge.
R410A can be added to a system the same as previous R22 systems, such that it can be added as a
liquid into the suction side if done slowly to allow the refrigerant to evaporate before entering the
compressor.
Superheat and Adjusting TXVs
Ideally, the best way to check the operation of the TXV is to measure the superheat at the evaporator
outlet. In many cases this is not convenient for the technician, since there may be no gauge ports
available. A superheat check at the condensing unit can be used instead. Since suction line lengths can
vary, so too can the superheat measured at the condensing unit. With short line lengths (less than 30 ft.),
the superheat should be between 10F and 15F. With longer suction line lengths (between 30 and 50 ft.)
superheats of 15F to 20F are normal.
In the example below, a standard gauge set is connected (blue to suction and red to liquid) to a system
operating on R410A refrigerant.
The suction line saturation temperature is reading approximately 44°F from the gauge. The surface
temperature of the suction line is reading 54.1°F. The surface temperature reflects the actual
temperature of the refrigerant. To calculate superheat, subtract the gauge temperature from the surface
temperature:
54.1°F – 44°F = 10.1°F of superheat
This should be compared to the unit recommendation, which in this case is 10°F.