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MPS
031413
Evacuation
Connect evacuation type four valve gauge manifold to high and low pressure service valve ports on the condensing
unit with the valve stems mid seated as when leak testing. Install service caps on valves and tighten them. Energize
the liquid line solenoid valve (make sure there is fresh oil in the vacuum pump). Connect a micron gauge directly to
of reading that vacuum. Connect the micron gauge to the access valve installed in the suction line at the evaporator.
Remove the Schrader valve depressors from the gauge hoses to reduce restriction and connect gauges to the suction
and liquid line service valve service ports on the condensing unit. Connect the pump to the 3/8” hose on the manifold
set, start the pump and run until the micron gauge reads 200 microns.
When a 200 micron level evacuation is achieved, break the vacuum with R-134a and add enough refrigerant to
pressurize the system with a few psi of positive pressure.
Charging
Remove the vacuum pump and the micron gauge. Install a spare low pressure gauge to the access valve at the
refrigerant to the system through the high pressure side,
Fill a wine bottle ¾ full with water between 60-75 degrees. Insert the bottle probe into the neck of the bottle as far as
possible. (It is important the bottle probe stopper is compressed by the neck of the bottle to ensure water will not leak
out.). Verify that the bottle probe is properly installed and the set point on the controller is low enough to allow the
system to run continuously for 30 minutes or more. Turn on power to the condensing unit and the compressor should
delay relay time to the lowest setting to avoid having to wait. Add refrigerant as a vapor through the low pressure side
of the system (suction service valve port).
Observe the sight glass when the compressor starts. If bubbles are present, slowly add more refrigerant in vapor
form to the low side. The suction pressure and head pressure should increase as the sight glass clears. Check the
superheat during the charging process. If the superheat drops to 4 or 5 degrees Fahrenheit and sight glass still has
bubbles, let the unit run until the wine cellar temperature drops and approaches 55 degrees Fahrenheit. Observe the
sight glass, if bubbles are present add additional refrigerant in small increments. Let the system stabilize for about 5
minutes and check the sight glass for bubbles before adding additional refrigerant. Once the sight glass is clear, check
the superheat at the outlet of the evaporator (evaporator superheat should be between 8-12 degrees Fahrenheit). If
superheat is not between 8 and 12 degrees make an adjustment to the expansion valve. Depending temperature, the
“high side” should be approximately 175lbs, and the “low side” should be 28lbs or more to keep the evaporator from
icing.
INSTALLING THE CONDENSING UNIT