Compressor Rotors; Rtaa Refrigerant And Oil Diagram - Trane RTAA-70 Installation & Maintenance Manual

Operating Principles

Compressor Rotors

The compressor is a semi-hermetic, direct-drive helical rotary type
compressor. Each compressor has two rotors - "male" and "female" - which
provide compression. See Figure 33 The male rotor is attached to, and driven
by, the motor, and the female rotor is, in turn, driven by the male rotor.
Separately housed bearing sets are provided at each end of both rotors.
The helical rotary compressor is a positive displacement device. The refrig-
erant from the evaporator is drawn into the suction opening at the end of the
motor barrel, through a suction strainer screen, across the motor, and into the
intake of the compressor rotor section. The gas is then compressed and
discharged directly into the discharge line.
There is no physical contact between the rotors and compressor housing.
The rotors contact each other at the point where the driving action between
the male and female rotors occurs. Oil is injected along the top of the
compressor rotor section, coating both rotors and the compressor housing
interior. Although this oil does provide rotor lubrication, its primary purpose is
to seal the clearance spaces between the rotors and compressor housing.
A positive seal between these internal parts enhances compressor efficiency
by limiting leakage between the high pressure and low pressure cavities.
Capacity control is accomplished by means of two unloader valve assemblies
in the rotor section of the compressor. The female rotor valve is a two-
position valve and the male valve is an infinitely variable position valve. See
Figure 33.
Figure 33

RTAA Refrigerant and Oil Diagram

68 RTAA-SVX01A-EN