JOHNSON CONTROLS
100
FORM100.50-EG12 (918)
4.
Low Ambient:
Compressors shall operate down to 0.0°F [optional] by monitor-
ing the refrigeration system discharge pressure and adjusting condenser airflow
to maintain the proper head pressure to protect compressor operation. Refrigerant
pressure transducers shall be included and provide the discharge pressure on the
single package unit control display.
5. I
n-Line Liquid Line Driers [replaceable core liquid line driers]:
Refrigerant pip-
ing includes check valves, thermal expansion valves with replaceable thermostatic
elements, high and low pressure switches, anti-recycling timing device to prevent
compressor restart for 5 minutes after shutdown.
6.
Condenser Wire Grill [optional louvered condenser enclosure or no enclo-
sure]:
The condenser section shall be enclosed by a wire grill [louvered or none]
condenser enclosure on the three exposed sides. Paint finish shall match the color
and salt spray specifications of the unit exterior.
7.
Hot Gas Bypass:
Hot gas bypass piping shall be provided to enable compressor
unloading to as low as 5% to better match cooling demand at low loads, prevent
excessive cycling of the compressor, and reduce the risk of coil freeze-up.
8.
Compressor sound treatment [optional]:
Compressor sound blankets shall be
provided to attenuate radiated sound from the compressors.
9.
Service Valves [optional]:
Liquid, suction and discharge service valves shall be
included to provide a means of isolating the refrigerant charge in the system so that
the refrigeration system may be serviced without removing the charge of the unit.
Controls
1.
Enclosure:
Unit shall be shipped complete with factory configured, installed, wired
and tested single package unit controller housed in a rain and dust tight enclosure
with hinged, latched, and gasket sealed door.
2.
Basic Controls:
Control shall include automatic start, stop, operating, and pro-
tection sequences across the range of scheduled conditions and transients. The
single package unit controller shall provide automatic control of compressor start/
stop, energy saver delay and anti-recycle timers, condenser fans, and unit alarms.
Automatic reset to normal operation after power failure. Software stored in non-
volatile memory, with programmed setpoints retained in lithium battery backed real
time clock (RTC) memory for minimum 5 years. Eighty character liquid crystal dis
-
play, descriptions and numeric data in English (or metric) units. The sealed keypad
shall include buttons for setpoints, display, entry, unit options & clock, and an on/
off switch.
3.
Diagnostics:
Upon startup, the controller shall run through a self-diagnostic check
to verify proper operation and sequence loading. The single package unit control
-
ler shall continually monitor all input and output points on the controller to maintain
proper operation. The unit shall continue to operate in a trouble mode or shut down
as necessary to prevent an unsafe condition for the building occupants, or to pre-
vent damage to the equipment. In the event of a unit shutdown or alarm, the oper
-
ating conditions, date and time shall be stored in the shutdown history to facilitate
service and troubleshooting.
Guide Specifications (Cont'd)
Содержание YPAL070
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