Ingersoll Rand VTR20 Manuel De Maintenance page 34

CONSTANT SPEED HEAD UNLOADER KITS
For Air Compressor Pump Models VTR & WTR
NOTE: This is optional equipment and may not be included on your unit.
The purpose of constant speed unloading is to provide a means of stopping or starting the
compression of air without stopping or starting the electric motor.
To accomplish this, an air pilot valve replaces the pressure switch used for stop-start operation.
The pilot valve senses storage tank pressure and when the pressure is raised to a predetermined
cut-out setting, the air is released to a suction unloader valve. The compressor stop compressing
air but continues to run until the pilot valve senses that the pressure in the tank has dropped to
the predetermined cut-in setting. At this time the air is released from the suction unloader valve
and the compressor starts compressing air again.
The parts called out below replace or are substituted for those found in the regular parts list.
IF3163 Rev A Page 34