Quincy Compressor QPHT 20, Operator'S Manual

July 2004

9

b. Remove compression fitting on the elbow 

attached to the particle strainer of the separator 
assembly by turning the hex head nut on the 
fitting. Remove the plastic tubing connecting the 
particle strainer and the drain valve solenoid.

c. Close the shut-off valve on the particle strainer, 

drain the down stream line of the particle strainer 
with the PUSH-TO-TEST button on the auto drain. 
Unscrew and clean out screen, replace screen 
and open shut-off valve.

d. Remove lower bowl bracket by unfastening the 

two machine screws and nuts that hold the lower 
bracket to the back panel.

e. Turn the separator bowl counterclockwise to 

remove. A pipe wrench may be necessary to 
remove the bowl.

NOTE: 

When reinstalling the separator bowl, make sure 

the O-ring is in place on the top of the bowl and that the 
O-ring seats properly on the separator housing. Air leaks 
may occur if O-ring is not seated.

f. Clean the bowl assembly with a mild soap 

solution and cold water.

g. Inspect the drain hoses for any kinks. Remove the 

drain hose inside the air dryer system and the 
drain hose outside the unit and blow into the line 
to clear any sediment or foreign material from the 
lines.

h. Reinstall the moisture separator bowl, the lower 

filter bracket, the particle strainer assembly, and 
the two drain hoses. If the separator still will not 
drain, contact Quincy or your distributor to order 
a new separator assembly.

6.

Condenser coil cleaning.

 Remove ambient filter 

(if equipped). Remove either the right or left side 
panel screws and panel. Using compressed air, 
blow collected dust and contamination off condenser 
from inside to outside.

7.

Hot gas bypass valve adjustment.

 The hot 

gas bypass valve adjustment regulates the flow of 
refrigerant through the air cooling system to maintain 
the proper suction pressure. The suction pressure 
must be maintained within the proper range for 
normal operation. The needle on the refrigerant 
suction pressure gauge should be in the blue or 
green zone depending on your air dryer system 
model.

a. Hot gas bypass valve adjustments must be made 

while the unit is operating. DO NOT TURN THE 
UNIT OFF.

b. Remove the left side panel on the cabinet. The 

hot gas bypass valve adjustment nut is located on 
the refrigerant discharge line near the 
compressor.

c. For Model QPHT-40: If the suction pressure 

gauge indicator arrow is below 52 PSIG, turn the 
adjusting nut CLOCKWISE. If the suction pressure 
gauge indicator needle is above 64 PSIG, turn 
the adjusting nut COUNTERCLOCKWISE. Let the 
unit operate for a few minutes and read the 
suction pressure gauge again. Continue to adjust 
the valve until the indicator arrow is in the 
GREEN ZONE between 52 PSIG and 64 PSIG. 
Adjust only 1/4 of a turn at a time. ALLOW 4 – 5 
MINUTES BETWEEN ADJUSTMENTS.

d. For Models QPHT-20, QPHT-60, QPHT-80, 

QPHT-100: If the suction pressure gauge 
indicator arrow is below 25 PSIG, turn the 
adjusting nut CLOCKWISE. If the suction pressure 
gauge indicator needle is above 33 PSIG, turn 
the adjusting nut COUNTERCLOCKWISE. Let the 
unit operate for a few minutes and read the 
suction pressure gauge again. Continue to adjust 
the valve until the indicator arrow is in the BLUE 
ZONE between 25 PSIG and 33 PSIG. Adjust 
only 1/4 of a turn at a time. ALLOW 4 – 5 
MINUTES BETWEEN ADJUSTMENTS.

The air dryer system will not operate
properly unless all panels are reinstalled
after any maintenance work.