Oil Reclaim System; Solid-State Starter; Controls; Definitions - Carrier 19EF Series Start Up & Operation Manual

Oil Reclaim System —
ates to return oil back to the oil reservoir by recovering it
from the compressor section.
During normal machine operation, refrigerant containing
a small amount of oil is pulled up from the cooler by the
compressor.
Oil reclaim is accomplished by returning the system oil
through the check valve. As oil builds up behind the second
stage impeller, it is drained by the check valve back into the
oil reservoir. An oil/refrigerant mixture is drawn up from the
operating level of the cooler and is discharged into the guide
vane housing. This assists the oil return system at low load
operating conditions.

SOLID-STATE STARTER

The 19EF may be supplied with a solid-state, reduced-
voltage starter. This starter provides on-off control of the com-
pressor motor as its primary function. Using this type of starter
reduces the peak starting torque, reduces the motor inrush
current, and decreases mechanical shock. This is summed
up by the phrase ''soft starting.''
Solid-state starters operate by reducing the starting volt-
age. The starting torque of a motor at full voltage is typically
125% to 175% of the running torque. When the voltage and
the current are reduced at start-up, the starting torque is re-
duced as well. The object is to reduce the starting voltage to
just the voltage necessary to develop the torque required to
get the motor moving. The voltage and current are then ramped
up in a desired period of time. The voltage is reduced through
the use of silicon control rectifiers (SCR). Once full voltage
is reached, a bypass contactor is energized to bypass the SCRs.

CONTROLS

Definitions
ANALOG SIGNAL — An analog signal varies in propor-
tion to the monitored source. It quantifies values between
operating limits. (Example: A temperature sensor is an ana-
log device because its resistance changes in proportion to
the temperature, generating many values.)
DIGITAL SIGNAL — A digital (discrete) signal is a 2-position
representation of the value of a monitored source. (Ex-
ample: A switch is a digital device because it only indicates
whether a value is above or below a set point or boundary
by generating an on/off, high/low, or open/closed signal.)
VOLATILE MEMORY — Volatile memory is memory in-
capable of being sustained if power is lost and subsequently
restored.
The memory of the PSIO and LID modules are volatile.
If the battery in a module is removed or damaged, all
programming will be lost.
General —
The 19EF hermetic centrifugal liquid chiller
contains a microprocessor-based control center that moni-
tors and controls all operations of the machine. The micro-
processor control system matches the cooling capacity of the
machine to the cooling load while providing state-of-the-art
machine protection. The system controls cooling load within
the set point plus the deadband by sensing the leaving chilled
water or brine temperature, and regulating the inlet guide
vane via a mechanically linked actuator motor. The guide
vane is a variable flow prewhirl assembly that controls the
refrigeration effect in the cooler by regulating the amount of
refrigerant vapor flow into the compressor. An increase in
guide vane opening increases capacity. A decrease in guide
vane opening decreases capacity. Machine protection is
provided by the processor which monitors the digital and
The oil reclaim system oper-
analog inputs and executes capacity overrides or safety shut-
downs, if required.
PIC System Components —
Control (PIC) is the control system on the machine. See
Table 1. The PIC controls the operation of the machine by
monitoring all operating conditions. The PIC can diagnose
a problem and let the operator know what the problem is and
what to check. It promptly positions the guide vanes to main-
tain leaving chilled water temperature. It can interface with
auxiliary equipment such as pumps and cooling tower fans
to turn them on only when required. It continually checks all
safeties to prevent any unsafe operating condition. It also
regulates the oil heater while the compressor is off, and the
hot gas bypass valve, if installed.
The PIC can be interfaced with the Carrier Comfort Net-
work (CCN) if desired. It can communicate with other PIC-
equipped chillers and other CCN devices.
The PIC consists of 3 modules housed inside the 3 major
components. The component names and the control voltage
contained in each component are listed below (also see
Table 1):
• control center
— all extra low-voltage wiring (24 v or less)
• power panel
— 115 v control voltage
— up to 600 v for oil pump power
• starter cabinet
— machine power wiring (per job requirement)
Table 1 — Major PIC Components and
Panel Locations*
PIC COMPONENT
Processor Sensor Input/Output Module (PSIO)

Starter Management Module (SMM)

Local Interface Device (LID)

6-Pack Relay Board

8-Input Modules (Optional)
Oil Heater Contactor (1C)
Oil Pump Contactor (2C)
Hot Gas Bypass Relay (3C) (Optional)
Control Transformers (T1-T4)
Control and Oil Heater Voltage Selector (S1)
Temperature Sensors
Pressure Transducers
*See Fig. 5-9.
PROCESSOR MODULE (PSIO) — The PSIO is the brain
of the PIC. This module contains all of the operating soft-
ware needed to control the machine. The 19EF uses 3 pres-
sure transducers and 8 thermistors to sense pressures and
temperatures. These are connected to the PSIO module. The
PSIO also provides outputs to the: guide vane actuator; oil
pump; oil heater; hot gas bypass (optional); and alarm con-
tact. The PSIO communicates with the LID, the SMM, and
the optional 8-input modules for user interface, starter man-
agement, and optional features.
STARTER MANAGEMENT MODULE (SMM) — This mod-
ule is located within the starter cabinet. This module ini-
tiates PSIO commands for starter functions such as start/
stop of the compressor, start/stop of the condenser and chilled
water pumps, start/stop of the tower fan, spare alarm con-
tacts, and the shunt trip. The SMM monitors starter inputs
such as flow switches, line voltage, remote start contact, spare
safety, condenser high pressure, oil pump interlock, motor
current signal, starter 1M and run contacts, and kW trans-
ducer input (optional). The SMM contains logic capable of
safely shutting down the machine if communication with the
PSIO is lost.
LOCAL INTERFACE DEVICE (LID) — The LID is mounted
to the control center and allows the operator to interface with
the PSIO or other CCN devices. It is the input center for all
local machine set points, schedules, set-up functions, and
8
The Product Integrated
PANEL
LOCATION
Control Center
Starter Cabinet
Control Center
Control Center
Control Center
Power Panel
Power Panel
Power Panel
Power Panel
Power Panel
See Fig. 5
See Fig. 5