Installation and Maintenance Manual

RTWD/RTUD Operating Principles
130 RLC-SVX09H-EN
The helical rotary compressor is a positive displacement
device.The refrigerant 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 rotors and
compressor housing. Rotors contact each other at the
point where the driving action between male and female
rotors occurs. Oil is injected along top of compressor rotor
section, coating both rotors and compressor housing
interior.Although this oil does provide rotor lubrication, its
primary purpose is to seal the clearance spaces between
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.
Oil Filter
Each compressor is equipped with a replaceable element
oil filter.The filter removes any impurities that could foul
the solenoid valve orifices and compressor internal oil
supply galleries.This also prevents excessive wear of
compressor rotor and bearing surfaces.
Compressor Rotor Oil Supply
Oil flows through this circuit directly from the oil filter,
through the master oil valve to the top of the compressor
rotor housing.There it is injected along the top of the
rotors to seal clearance spaces between the rotors and the
compressor housing and to lubricate the rotors.
Compressor Bearing Oil Supply
Oil is injected into the bearing housings located at each
end of both the male and female rotors. Each bearing
housing is vented to compressor suction, so that oil
leaving the bearings returns through the compressor
rotors to the oil separator.
Oil Separator
The oil separator consists of a vertical tube, joined at the
top by the refrigerant discharge line from the compressor.
This causes the refrigerant to swirl in the tube and throws
the oil to the outside, where it collects on the walls and
flows to the bottom.The compressed refrigerant vapor,
stripped of oil droplets, exits out the top of the oil
separator and is discharged into the condenser.
Compressor Loading Sequence
The customer has the option to choose either Fixed
Sequence or Balanced Start and Hours.
Fixed Sequence. When Balanced Starts and Hours is
disabled, the controls will operate with Fixed Sequence
compressor loading. Whichever compressor that is
selected to be the lead compressor will start first on a
command for cooling, unless it is locked out. Compressors
will be unstepped and stopped in reverse order.
Balanced Starts and Hours. When Balanced Starts
and Hours option is enabled, the controls will start the
compressor with the lowest Start Bid, defined as:
Compressor X Start Bid =
(# of Starts for Compressor X) +
(Accumulated Running hours for CompressorX/10)
If the compressor with the lowest Start Bid is unavailable
due to a circuit lockout, circuit diagnostic, or compressor
diagnostic, the compressor with the next lowest Start Bid
will be started.
Once compressors are running, and demand is decreased,
the compressor to unstage or turn off next will be, in order
of priority:
1. Any compressor running at minimum load.
2. The compressor with the greatest hours.
Figure 51. RTWD/RTUD compressor
Suction
Strainer
Motor
Rotor
MotorTerminals
Discharge
Check Valve
Male Unloader
Oil Filter
Female
Oil Control Valve (hidden)
Male Rotor
Female
Rotor
Piston
Unloader
Piston