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Component Operation and Maintenance, Checks and Adjustments
53
Adjustment
To adjust the superheat setting, proceed as follows:
1. Remove the valve cap at the bottom of the valve.
2. Turn the adjusting stem counterclockwise to lower the superheat.
3. Turn the adjusting stem clockwise to increase the superheat.
7.4.6 Hot Gas Bypass Valve
Operation
The hot gas bypass is inserted between the compressor discharge line and the leaving side of the
expansion valve through the side outlet distributor (refer to Figure 7). The system, during normal
operation, when the evaporator is under full load, will maintain enough pressure on the leaving side
of the hot gas valve to keep the valve port closed.
If the load on the evaporator decreases, the evaporator will get colder. When the coil is too cold, the
internal pressure in the evaporator drops and allows the hot gas bypass valve to open. Hot gas then
mixes with the liquid coolant on the discharge side of the expansion valve, raising the temperature
and pressure in the evaporator. The net result is a reduction in the cooling capacity of the unit to
match the load.
Adjustment
Upon deciding what evaporator temperature is desired, the following procedure should be used to
adjust the hot gas bypass valve:
1. Install the suction and discharge pressure gauge.
2. Turn thermostat to call for cooling so that the refrigeration compressor will run.
3. Remove the TOP adjusting nut from the valve.
4. Insert an Allen wrench in the brass hole at top of valve in adjusting port, and turn CLOCKWISE
if a higher evaporator temperature is required.
5. After obtaining the suction pressure required, reinstall cap tightly making sure there are no
leaks.
6. Let the evaporator operate for approximately 10 to 15 minutes to make sure the suction pressure
is within the range desired.
7. There will be a fluctuation of approximately 3 to 6 PSIG (21 to 41 kPa) on the evaporator due to
the differential on the hot gas bypass.
Figure 7 Hot gas bypass
NOTE
Make no more than one turn of the stem at a time. As long as thirty minutes may be required
for the new balance to take place.
Solenoid Valve
Condenser
Compressor
Discharge
Bypass Valve
TEV
Side Distribution
Connector or ASC
Hot Gas
Solenoid Valve
Evaporator
External
Equalizer
External Equalizer