SERVICING
4.Review the technical information manual or specification sheet for the model being serviced to obtain the design subcooling.
5.Compare the
Alternately you can convert the liquid line pressure gauge reading to temperature by finding the gauge reading in Temperature - Pressure Chart and reading to the left, find the temperature in the °F. Column.
6.The difference between the thermometer reading and pressure to temperature conversion is the amount of subcooling.
Add charge to raise subcooling. Recover charge to lower subcooling.
Subcooling Formula = Sat. Liquid Temp. - Liquid Line
Temp.
EXAMPLE:
a.Liquid Line Pressure = 417
b.Corresponding Temp. °F. = 120°
c.Thermometer on Liquid line = 109°F.
To obtain the amount of subcooling subtract 109°F from 120°F.
The difference is 11° subcooling. See the specification sheet or technical information manual for the design subcooling range for your unit.
S-109A TWO SPEED APPLICATION
Run the remote on low stage cooling for 10 minutes until refrigerant pressures stabilize. Follow the guidelines and methods below to check unit operation and ensure that the refrigerant charge is within limits. Charge the unit on low stage.
1.Purge gauge lines. Connect service gauge manifold to
2.Temporarily install thermometer on liquid (small) line near liquid line service valve with adequate contact and insulate for best possible reading.
3.Check subcooling and superheat. Systems with TXV application should have a subcooling of 5 to 7 ºF and superheat of 7 to 9 ºF.
a.If subcooling and superheat are low, adjust TXV to 7 to 9 ºF superheat, then check subcooling.
NOTE: To adjust superheat, turn the valve stem clockwise to increase and counter clockwise to decrease.
b.If subcooling is low and superheat is high, add charge to raise subcooling to 5 to 7 ºF then check superheat.
c.If subcooling and superheat are high, adjust TXV valve to 7 to 9 ºF superheat, then check subcooling.
d.If subcooling is high and superheat is low, adjust TXV valve to 7 to 9 ºF superheat and remove charge to lower the subcooling to 5 to 7 ºF.
NOTE: Do NOT adjust the charge based on suction pressure unless there is a gross undercharge.
4.Disconnect manifold set, installation is complete. Subcooling Formula = Sat. Liquid Temp. - Liquid Line Temp.
S-110 CHECKING EXPANSION VALVE OPERATION
1.Remove the remote bulb of the expansion valve from the suction line.
2.Start the system and cool the bulb in a container of ice water, closing the valve. As you cool the bulb, the suction pressure should fall and the suction temperature will rise.
3.Next warm the bulb in your hand. As you warm the bulb, the suction pressure should rise and the suction tem- perature will fall.
4.If a temperature or pressure change is noticed, the expansion valve is operating. If no change is noticed, the valve is restricted, the power element is faulty, or the equalizer tube is plugged.
5.Capture the charge, replace the valve and drier, evacuate and recharge.
S-111 FIXED ORIFICE RESTRICTOR DEVICES
The fixed orifice restrictor device (flowrator) used in conjunc- tion with the indoor coil is a predetermined bore (I.D.).
It is designed to control the rate of liquid refrigerant flow into an evaporator coil.
The amount of refrigerant that flows through the fixed orifice restrictor device is regulated by the pressure difference between the high and low sides of the system.
In the cooling cycle when the outdoor air temperature rises, the high side condensing pressure rises. At the same time, the cooling load on the indoor coil increases, causing the low side pressure to rise, but at a slower rate.
Since the high side pressure rises faster when the tempera- ture increases, more refrigerant flows to the evaporator, increasing the cooling capacity of the system.
When the outdoor temperature falls, the reverse takes place. The condensing pressure falls, and the cooling loads on the indoor coil decreases, causing less refrigerant flow.
A strainer is placed on the entering side of the tube to prevent any foreign material from becoming lodged inside the fixed orifice restriction device.
If a restriction should become evident, proceed as follows: 1. Recover refrigerant charge.
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