12
Pub. No. OM-A-75 REV. 4 — March 2006
COMPRESSOR
Refrigerant compressors normally do not need any
maintenance. The compressor will unload or adjust for
different load conditions with the refrigeration controls.
Any time power is applied to the compressor, and the
suction pressure is higher than the specified readings, the
compressor is either not pumping or failed electrically, or
tripped “off” at the overload protection. If the compressor
does not automatically reset within a few minutes, it
requires servicing. Service must be performed by a
qualified refrigeration technician.
EXPANSION VALVE
Air dryers equipped with an automatic expansion valve
are factory adjusted for proper cooling. The valve
adjusting stem is secured with a lock nut at the factory to
maintain proper setting. Larger units are equipped with a
thermostatic expansion valve, factory set to maintain a
superheat of 8 to 10°F. These valves do not need
adjustment in normal operation. Generally, superheat
adjustments are needed only at the time of valve
replacement. Expansion valve service must be performed
by a qualified refrigeration technician.
HOT GAS BYPASS VALVE
Model AD-10 and larger air dryers come equipped with
modulating hot gas bypass valves. This valve maintains
the refrigerant suction pressure in varying load conditions.
The dryer will run from no load to full load conditions
without freeze-up. The operation of this valve is automatic.
If the valve needs adjustment, turn the adjusting
stem clockwise to raise the suction pressure, and
counterclockwise to lower the suction pressure. This
adjustment should be made under a no-load condition if
possible. When the adjustment is made, turn one quarter
of a turn at a time, and wait 3 to 5 minutes between
adjustments. Once the adjustment is complete, secure the
adjusting stem with the locknut that is provided. Careful
adjustment of this valve is necessary for normal operation
of the air dryer. Hot gas bypass valve adjustment may be
made by maintenance personnel. (See Figure 5.)
FIGURE 5 — HOT GAS BYPASS VALVE ADJUSTMENTS
3/8" HEX.
ADJUSTMENT
*
5/16" ALLEN
WRENCH
ADJUSTMENT
*
3/16" ALLEN
WRENCH
ADJUSTMENT
*
*
ADJUSTMENT POINT
