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O O p p e e r r a a t t i i n n g g P P r r i i n n c c i i p p l l e e s s
refrigeration system and generate a non-latching
diagnostic—Purge Liquid Level Too High Warning. If
the float switch has re-closed after 20 minutes, the
purge controls will restart the refrigeration system.
If the float switch remains open for more than
20 minutes, or if the float switch/liquid level restart
cycle has occurred more than four times in four hours,
a latching diagnostic—Purge Liquid Level Too High
Continuously—will be generated. The purge system
will not restart until it is reset.
If a Purge Liquid Level Too High Continuously
diagnostic occurs, check the purge lines for any type of
restriction (trapped liquid, closed valves, etc.) and
ensure that the filter-drier on the liquid return line is in
good condition.
A UL-required pressure-relief device (fusible plug),
which protects against over-pressurization of the purge
tank, is mounted on the purge tank. The plug material
will fuse at 210°F (98.9°C), which equates to
approximately 132 psig (910.1 kPaG) for refrigerant R-
1233zd.
Pump-out Subsystem
When the purge control subsystem detects the
presence of non-condensables in the purge tank, the
pump-out solenoid and exhaust solenoid valves open,
and the pump-out compressor turns on. The valves and
the compressor cycle on and off as needed to achieve
an efficient and fast removal of non-condensables.
N N o o t t e e : : A High Vacuum Pump option is available for
applications that require purge operation at low
condensing temperatures and pressures. This
option provides a two-stage pump-out
compressor. The High Vacuum Pump option
allows the purge system to operate to saturation
temperatures as low as 34°F (1.1°C). Typical
applications that may require the High Vacuum
Pump option include free-cooling installations,
series chiller installations, ice systems having
brine flowing through idle chillers, chillers
installed outdoors or in unconditioned spaces, or
any application that may cause very low
condenser water temperatures.
Carbon Tank and Regeneration Subsystem
The discharge from the pump-out compressor is piped
through the carbon tank. The special carbon in the tank
effectively scrubs and collects refrigerant molecules
from the non-condensable gas before the gas passes
through the exhaust solenoid valve to the chiller vent
line.
A 175 W resistive heater is mounted inside the carbon
tank and is used to periodically "regenerate" the
carbon bed and drive any collected refrigerant vapor
back into the chiller. A UL-required pressure-relief
valve, rated at 150 psig (1034.2 kPaG), is mounted on
the line leaving the carbon tank. The valve protects
against over-pressurization of the carbon tank.
84
A temperature sensor is installed through the top of the
carbon tank shell so that the controls can monitor the
carbon bed temperature. The temperature sensor
controls the regeneration cycle and protect against
overheating. If the limit temperature is reached, the
system shuts down and a Purge Carbon Regen
Temperature Limit Exceeded diagnostic is generated.
Sensors
The following sensors are used to enable control
communication between the Tracer® UC800 controller
and the EarthWise™ purge system. The sensors use
low-level intelligence devices (LLIDs) to communicate
with the Tracer® UC800 controller.
•
C C o o m m p p r r e e s s s s o o r r s s u u c c t t i i o o n n t t e e m m p p e e r r a a t t u u r r e e s s e e n n s s o o r r . . This
sensor is mounted on the purge condensing unit
suction line. The controller uses the value of this
temperature sensor to decide whether or not to
purge non-condensables from the purge tank.
When the temperature drops to a specified point,
the controller activates the pump-out cycle to
remove the accumulated non-condensables from
the purge tank. When enough non-condensables
have been removed and the purge compressor
suction temperature increases in response, the
controller terminates the pump-out cycle.
•
S S a a t t u u r r a a t t e e d d c c o o n n d d e e n n s s e e r r t t e e m m p p e e r r a a t t u u r r e e s s e e n n s s o o r r . . This
sensor is mounted on the chiller. If the chiller is
running, the controller uses the value of this
temperature sensor to adjust the purge pump-out
initiate/terminate setpoints. It may be used to
prohibit pump-out if system conditions are too cool.
•
S S a a t t u u r r a a t t e e d d e e v v a a p p o o r r a a t t o o r r t t e e m m p p e e r r a a t t u u r r e e s s e e n n s s o o r r . . This
sensor is mounted on the chiller. If the chiller is off,
the controller uses the value of this temperature
sensor to adjust the purge pump-out initiate/
terminate setpoints. It may be used to prohibit
pump-out if system conditions are too cool.
•
C C a a r r b b o o n n t t a a n n k k t t e e m m p p e e r r a a t t u u r r e e s s e e n n s s o o r r . . This sensor is
mounted in the carbon tank of the purge system. It
provides feedback to the carbon regeneration
algorithm. The sensor and the controller function
much the same as a thermostat to control the
carbon tank heater.
•
L L i i q q u u i i d d l l e e v v e e l l s s e e n n s s o o r r . . This sensor resides in the
purge control panel. It monitors the status of the
normally closed float switch, which is mounted in
the bottom of the purge tank. If an adequate
amount of liquid fails to drain from the purge tank,
the float switch and sensor detect the condition and
prevent further purge operation.
•
C C o o n n d d e e n n s s i i n n g g u u n n i i t t L L L L I I D D . . This LLID resides in the
purge control panel. It uses a high-power relay to
control the operation of the purge condensing unit.
•
Q Q u u a a d d r r e e l l a a y y L L L L I I D D . . This LLID resides in the purge
control panel. It has four relay outputs that are used
to control the pump-out compressor, the carbon
CVHH-SVX001G-EN
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