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On style D and later chillers, the oil pump is driven
by a Variable Speed Drive (VSD) (Refer to Service
Man u al 160.52-M2 for details of this device). In nor mal
op er a tion, the oil pump speed is au to mat i cal ly con trolled
to main tain a desired oil pres sure. The speed can be
man u al ly con trolled with the Keypad keys using the Oil
Sump Screen with Ser vice access level.
On those chillers equipped with the oil pump VSD, the
VSD operation as described below must be EN ABLED
by placing Microboard Program Switch SW1-2 in the
ON position. Those chillers not equipped with the oil
pump VSD must have this operation DISABLED by
plac ing SW1-2 in the OFF position. Refer to Table 2,
"Microboard Program Switches".
The programming of the Setpoints referred to below is
performed on the Oil Sump Screen using instructions
in the "System Calibration, Service Setpoints and Re set
Procedures" section of this book. These Setpoints should
not be programmed by anyone other than a qual i fi ed Ser-
vice Technician. Variable speed oil pump chill ers are not
equipped with the Liquid Line Solenoid Valve (2SOL),
or High Speed Thrust So le noid Valve (4SOL). There-
fore, when Oil Pump VSD operation is ENABLED with
Program Switch SW1-2, the Program is con fi g ured to
operate the chiller without these so le noid valves. Op-
er a tion Sequence Timing Diagrams in Fig. 4 and 5 depict
chiller operation with the Oil Pump VSD enabled or
disabled. Also, when equipped with the oil pump VSD,
the Microboard, under Program con trol, controls the Oil
Heater to maintain a specifi c oil temperature as de scribed
in the "Oil Heater" sec tion below.
AUTOMATIC OPERATION
Under Program control, a speed command signal from
the Microboard controls the oil pump speed by vary ing
the VSD output frequency. The speed command is in
the form of a Pulse Width Modulation (PWM) Sig nal
as explained below. During the System Prelube period
and the fi rst 15 seconds of System Run, the Pro gram
operates the oil pump VSD over the range of 25 Hz to 60
Hz to maintain the oil pressure to the target value of 45
PSID. For the remainder of System Run and the Coast-
down period, it operates it over the same fre quen cy
range to maintain the pressure to the pro grammed Oil
Pressure Setpoint.
YORK INTERNATIONAL
SECTION 15
OIL PUMP VARIABLE SPEED DRIVE
(REFER TO FIG. 53 - 55)
When the chiller is started, 13 seconds after the Sys tem
Prelube is initiated, the Microboard (J20-3) starts the oil
pump by driving the EN (enable) input of the Oil Pump
VSD to a Logic Low level (<1VDC). The Microboard
(J20-1) then applies a speed command sig nal to the
PWM input of the VSD that ramps the VSD output fre-
quen cy from 25 Hz (45 Hz on all "P" com pres sors. 45 Hz
on other compressor applications equipped with Flash
Memory Card version C.MLM.01.05.xxx and later) to
what ev er fre quen cy is re quired (up to a max i mum of 60
Hz) to achieve the Target Oil Pressure. (If equipped
with Flash Memory card version C.MLM.01.08.xxx
(and later), it is held at 45Hz for 8 seconds before re-
leasing to normal control). The Tar get Oil Pres sure is
fi xed at 45 PSID. The speed com mand is dis played on
the Oil Sump Screen as OIL PUMP DRIVE COM-
MAND FRE QUEN CY = XX HZ. The speed command
to the VSD is mod u lat ed as re quired to main tain the 45
PSID Target Oil Pressure for the re main der of System
Prelube and the fi rst 15 sec onds of Sys tem Run. While
this target is in effect, it is dis played on the Oil Sump
Screen as TARGET OIL PRES SURE = 45 PSID. The
time re main ing that the Target Oil Pres sure is in effect is
displayed as a count down timer in the message PULL-
DOWN TIME RE MAIN ING = XX SEC. After the
com pres sor has been run ning for 15 seconds, the speed
of the VSD is con trolled to main tain the pro grammed Oil
Pres sure Setpoint (20 to 45 PSID). This is dis played on
the Oil Sump Screen as SETPOINT OIL PRES SURE
= XX PSID.
During Oil Pump operation, the following minimum and
maximum oil pressures are allowed:
1. During Automatic operation, if either of the fol-
lowing conditions occur, a Safety shutdown is per-
formed and OIL - VARIABLE SPEED PUMP
- PRESSURE SETPOINT NOT ACHIEVED
is dis played. These conditions are not checked in
MANUAL operation.
a. If the Oil Pressure is <35 PSID (25 PSID on
"P" compressors) for 5 continuous seconds
during the last 10 seconds of System Prelube
or dur ing the fi rst 15 seconds of System Run.
b. If the Oil Pressure is < the programmed Oil
Pressure Setpoint and the speed command is
at 60 Hz for 5 continuous seconds, any
time after the fi rst 30 seconds of SYSTEM
RUN.
FORM 160.54-M1(503)
15
95
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