Wine Guardian SP25 Installation, Operation And Maintenance Manual page 31

the system has been sufficiently charged. HOWEVER, a full sight glass or a glass with
bubbles does not necessarily indicate the system is properly charged or
undercharged. There may be other factors affecting sight glass, so do not charge by
sight glass method only. A full sight glass matched with proper system pressures, sub-
cooling, and superheat values is the proper method for confirming that the system
charge is correct for your application.
If you are not sure how to measure superheat or sub-cooling:
Superheat
• Get an accurate suction line temperature on the suction line as close to the
compressor inlet as possible. At the same time, attach a compound pressure
gauge set to the system to read the low-side suction pressure at the suction
service valve port (back seated valve stem to allow unrestricted refrigerant flow
from evaporator back to the compressor). Convert suction pressure to a
saturated temperature as derived from a pressure/temperature chart. Since the
suction line temperature is the higher value, subtract the saturated temperature
from it to derive your superheat. If your wine cellar is already at specified
conditions e.g., 57°F (13°C), 55% RH) and if your superheat is very low, or zero,
you may have overcharged your system.
Sub-Cooling
• With your compound pressure gauge set installed with the high-side connect to
the valve port on the liquid receiver (back seated valve stem to allow un-
restricted refrigerant flow from condenser to evaporator). Convert this liquid
pressure to a saturated temperature from pressure/temperature chart. Next,
obtain your liquid-line temperature by getting an accurate reading on the liquid
line BEFORE the TXV expansion on the indoor side. Obtain this temperature
entering the evaporator unit. Subtract the liquid line temperature from the
saturated liquid temperature to derive the system sub-cooling.
System Charging Amount:
Each DS & WGS Model condensing unit is shipped with 16oz/.453kg of refrigerant
charge already, to be considered for below total amounts based on 25'/7.62 meters
interconnect length.
For system charge adjustments compared to 25'/7.62 meters factory baseline:
DS025, WGS40 if 1/4"/.635cm OD (outside diameter) liquid line, adjustments will be ~
.50oz/foot & .0465kg/meter.
For reference: The suggested total system charge based on factory testing using 25ft
(7.62 meters) of interconnected piping is in table below.
SP25 59-Ounce Total Charge
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