RWB II PLUS MICROPROCESSOR CONTROL
OPERATION
S70-200 OM
Page 7
PRELUBE, FULL LUBE, or CYCLING - Pump type will be
indicated.
PGM/ - Microprocessor Program version.
LIQ INJ CON - The Liquid Injection Control, reported in de-
grees Fahrenheit, will shut off the liquid refrigerant supply
to the compressor if the oil temperature equals or falls be-
low this setpoint.
FILTER - The Oil Filter setpoint will trigger an alarm when
the differential pressure across the oil filter equals or ex-
ceeds 25 pounds per square inch (PSI) for 15 seconds, or
longer.
OIL HEATER - The Oil Heater setpoint, reported in degrees
Fahrenheit, turns on the oil separator heater(s) when the oil
temperature equals or falls below this setpoint whenever
the compressor is NOT running.
Compressor Differential Cutout - The differential cutout
has been lowered from 55 lb to 25 lb. Cutout will occur after
five minutes. To allow operation at low differential pressures,
the micro will take the following steps:
A. Force unload the compressor to 50% and display an "F
Unload" when the oil pressure is within 10 lb of the main oil
injection port pressure and the slide valve position is greater
than 50%.
B. Prohibit the compressor from loading and display a "Ld
Inhib" message when the differential is within 15 lb of the
main oil injection port pressure.
Oil Pressure Alarm and cutout - Logic has been revised
to same logic as currently used on RXB/RXF. The new logic
is as follows:
Prelube and Cycling Oil Pump version when pump is not
running. Alarm will occur if oil pressure is 25 lb below dis-
charge pressure or within 10 lb of suction pressure for 30
seconds. Cutout occurs if oil pressure is 30 lb below dis-
charge pressure or if oil pressure is within 7 lb of suction
pressure for 10 seconds and alarm has already been set.
Full Lube and Cycling Oil Pump version when oil pump is
running. Alarm occurs if oil pressure is within 10 lb of dis-
charge pressure for 30 seconds. Cutout occurs when oil
pressure is within 5 lb of discharge pressure for 10 seconds
and oil pressure alarm has been set.
Cycling Oil Pump Control - The oil pump will cut off when
differential pressure between suction and discharge pres-
sure is 55 lb or greater. Upon pump termination the above
cutout logic (pump not running) is utilized. Pump cut-in oc-
curs when the differential pressure between suction and dis-
charge is 45 lb or less. Oil pressure alarm and cutout logic
(pump running) begins after a 30 second delay which al-
lows the oil pump to build pressure.
HOW TO DETERMINE
ADJUSTABLE SETPOINTS:
Adjustable Setpoints should reflect values compatible with
normal system operation. Too high a Low Suction Pressure
Alarm setpoint may cause nuisance prealarms. Similarly,
cutout setpoints should not fall within what are considered
normal plant operation. As a rule of thumb, set the Low Suc-
tion Pressure Alarm 5 PSIG lower than the lowest normal
suction pressure. The Low Suction Pressure Cutout should
be 5 to 10 PSIG lower than the Low Suction Pressure Alarm
setpoint.
The High Discharge Pressure Cutout should be set at 90%
of the setting of the lowest high side relief valve. The High
Discharge Pressure Alarm should be set 10 PSIG lower than
the Cutout.
The Capacity Control setpoint should be the equivalent of
the normal suction condition.
FIXED SETPOINTS DISPLAY *
FIXED SETPOINTS: HIGH STAGE PRELUBE
OIL PUMP PGM/A
Hi Disch Cut----[212F]
Hi Disch Alarm--[194F] Liq Inj Con 113F
Hi Oil Temp Cut-[167F] Filter------[25]
Hi Oil Temp Alarm[158F]Oil Heater[113F]
Lo Oil Temp Cut--[49F] Lo Oil Cut-[030]
Lo Oil Temp Alarm[58F] Lo Oil Alrm[025]
The Fixed Setpoints display lists all fixed setpoints, program
version, plus low oil alarm and low oil cutout setpoints. Fixed
Setpoints define the limits of acceptable compressor opera-
tion. Fixed Setpoints are factory determined, stored in pro-
grammed memory (PROM), and will remain in memory if
power to the microprocessor is interrupted.
HI DISCH CUT - The High Discharge Temperature Cutout,
reported in degrees Fahrenheit, will shut down the com-
pressor if the discharge temperature equals or exceeds this
setpoint.
HI DISCH ALARM - The High Discharge Temperature Alarm,
reported in degrees Fahrenheit, will trigger a prealarm if the
discharge temperature equals or exceeds this setpoint.
HI OIL TEMP CUT - The High Oil Temperature Cutout, re-
ported in degrees Fahrenheit, will shut down the compressor
if the oil temperature equals or exceeds this setpoint.
HI OIL TEMP ALARM - The High Oil Temperature Alarm,
reported in degrees Fahrenheit, will trigger a prealarm if the
oil temperature equals or exceeds this setpoint.
LOW OIL TEMP CUT - The Low Oil Temperature Cutout,
reported in degrees Fahrenheit, will shut down the com-
pressor if the separator oil temperature equals or falls be-
low this setpoint.
LOW OIL TEMP ALARM - The Low Oil Temperature Alarm,
reported in degrees Fahrenheit, will trigger a prealarm if the
separator oil temperature equals or falls below this setpoint.
HIGH STAGE or BOOSTER - Compressor application indi-
cator.
*Display for illustrative purposes only.
