It is critical to have the poppet end of the differential check valve installed toward the wet tank or toward the air dryer outlet or air dryer failure can occur.
The Holset® E-Type system air compressor is an engine drive, piston type compressor which supplies compressed air to operate air activated devices. The compressor operates continuously, but has a loaded and unloading operating mode. The operating mode is controlled by a pressure activated governor and the compressor unloading assembly.
Intake air can come from the intake manifold or near the engine air cleaner.
For E-Type unloader system used with an air dryer, an Econ valve, and check valve with makeup line must be installed in the air system, or an approved dryer incorporating all valves must be used.
The Econ valve must be mounted in a position and altitude to avoid collecting condensation which can freeze during cold weather. The Econ valve must be installed with its inlet port above the outlet port to avoid condensation traps in the discharge line or fittings, per normal recommended installation practice for air compressor discharge lines.
The air inlet temperature for the Econ valve must not exceed the inlet air maximum temperature recommendation of the air dryer manufacturer. When possible, the Econ valve must be 610 to 2134 mm [2 to 7 ft] from the air compressor or the air dryer must be 2438 to 3048 mm [8 to 10 ft] from the air compressor. The air discharge line must be downward sloping from the air compressor outlet air port to the air dryer inlet air port.
The Holset® differential check valve must be installed either on the upper part of the wet tank, or on the side of the dryer outlet fittings to avoid condensed moisture (see illustrations that follow).
NOTE: Use of a differential check valve other than the Holset® identified part, can result in system malfunction. Contact the air dryer manufacturer for recommendation.
NOTE: To prevent overnight or shutdown freeze-ups of the Econ valve not conforming to the 610 to 2134 mm [2 to 7 ft] Econ valve location, make sure that the vehicle wet tank is drained to below governor cut-in pressure (via wet tank drain valve) following vehicle shutdown. This action will open the Econ valve and allow compressor air flow at vehicle start-up.
Performance Rating Data
Holset® SS191 A/C Model
Holset® SS296, SS296E, and SS338E A/C Model
Holset® ST676 A/C Model
Holset® ST773 A/C Model
Holset® QE230 A/C Model
Holset® QE230, QE296, and QE338 A/C Model
The following illustration applies to the Holset® QE338 air compressor:
Last Modified: 13-Jun-2005