16
JOHNSON CONTROLS
FORM 201.21-NM4 (616)
16
JOHNSON CONTROLS
PRODUCT DESCRIPTION
Oil Cooling
Oil cooling is provided by routing oil from the oil sepa-
rator through several of the top rows of the condenser
coils and back to the compressor.
Capacity Control
When cooling is needed, one or more compressors,
as determined by the system microprocessor based on
deviation from setpoint, will start at minimum speed
with low inrush current. Variable speed operation of
the compressor reduces the capacity and allows smooth
balancing of the compressor capacity with the cooling
load.
Capacity control is accomplished by varying the number
of compressors and the speed of the compressors with
the VSD to promote stable, smooth, and precise load-
ing/unloading.
Hot Gas Bypass is not required with VSD control of
the compressors.
The chiller is available with Standard IPLV or High IPLV
software (EPROM). High IPLV software optimizes the
performance of the chiller capacity and fan controls.
High IPLV chillers also require additional factory
programming.
Power and Control Panel
All controls and the VSD are factory-wired and function
tested. The panel enclosures are designed to NEMA 3R
(IP65) rating and are manufactured from powder-painted
steel with hinged, latched, and gasket sealed outer doors
with wind struts for safer servicing.
The Power and Micro Control Panels are combined into
a single control/power cabinet and include Compressor
VSD Controls, Chiller Microprocessor Controls, Fan
Controls, and all other chiller controls.
The Display and Keypad are accessible through an
access door without opening the main doors to the
electrical cabinet.
Each Power Compartment Contains
Incoming single point power is standard utilizing either
a lockable circuit breaker or terminal block, 115VAC
control transformer, VSD, fan contactors, ON/OFF unit
switch, microcomputer keypad and display, Chiller Con-
trol and VSD Logic boards, 1 or 2 SCR trigger control
boards and relay boards.
Current transformers sense each phase of motor current,
and send corresponding signals to the Chiller Logic
Board. Current monitoring protects the compressor
motors from damage due to: low motor current, high
motor current, short circuit current, single phasing, and
compressor overload.
Short Circuit Withstand Rating of the chiller electrical
enclosure is 30,000 Amps for standard terminal block
connection. Ratings are in accordance with UL508C.
A Circuit Breaker Option can be added to increase the
Short Circuit Withstand Rating to 200/230V = 100,000
Amps, 380/460 V = 65,000 Amps, and 575V = 42,000
Amps.
Microprocessor and VSD Controls
Microprocessors on the Chiller Control Board and
VSD Logic Board control starting, stopping, loading,
unloading, safeties, and chilled liquid temperature
control. Chilled liquid control decisions are a function
of temperature deviation from setpoint and the rate of
change of temperature.
The standard controls include: brine chilling, thermal
storage, run signal contacts, unit alarm contacts, chilled
liquid pump control, automatic reset after power fail-
ure, automatic system optimization to match operating
conditions.
Remote cycling, optional current limiting, optional
temperature setpoint reset, and optional remote sound
limit can be accomplished by connecting user-supplied
signals to the microprocessor.
Unit operating software is stored in non-volatile
memory. Field programmed setpoints are retained in
lithium battery backed real time clock (RTC) memory
for 10 years.
