Zero Zone Highlight MERCHANDISER RHZC30, Руководство по установке и эксплуатации

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16 • Installation & Operation
INSTALLATION & OpERATION
An adjustable defrost termination thermostat is an available option from Zero Zone. If the case is so equipped, the defrost termination
temperature is 65°F at the dump line. Contractor should verify the 65°F setting.
Electric Defrost Operation
The compressor stops when the defrost is initiated in a non-pump-down system. On pump-down systems, the liquid line solenoid will be de-
energized when the defrost is initiated. The clock will energize the 208/230 volt defrost heater, and energize the normally closed 208/230 volt
contactor or relay. This de-energizes the 115-volt fans, lights, and anti-sweat heaters. If you don’t have a light circuit limit thermostat, the lights
will not de-energize.
After the defrost period, the compressor will operate. When the coil temperature r5°F, the fan thermostat (Klixon) will close, starting the
fans. See Figure 34 on page 48 .
Gas Defrost Operation
Several types of gas defrost methods (using time-actuated, time-terminated, or temperature-terminated defrost timers) can be used to defrost
the evaporator.
The refrigeration system designer and installer are responsible for correct line sizing for effective gas defrost and liquid return from the freezers.
Sizing and component selection depend on the type of defrost, size, and location of high side refrigeration system.
Zero Zone freezers equipped for gas defrost consist of a side port distributor and a TXV check valve for coil defrost, and a suction line check
valve to bypass hot gas to the serpentine coil. The serpentine coil is attached to the bottom of the pan to ensure pan and drain defrost.
The timer starts the gas defrost cycle by energizing a solenoid, reversing valve, or directional valve. The gas is injected from the source into
the suction line of the evaporator to be defrosted. The gas flows into the serpentine coil attached to the floor of the case and then into the
evaporator. Condensed liquid leaves the evaporator through the side port distributor, through a check valve into the liquid line. See Figure 33
on page 47 .
General Notes
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The refrigeration technician should recheck coil condition after one week of retail operations to be certain that the frequency and duration
of defrost is adequate for the particular store and conditions. For example, if defrost voltage is below 200 volts, additional fail-safe time
may be required.
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When using time-terminated defrost, defrost termination thermostat should be wired in series with the defrost heater.
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Defrost termination thermostats may be wired in series for multiple evaporator installations.
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Defrost termination thermostats may be used as a digital input for electronic controllers.
Limit Thermostat
The Zero Zone standard case includes a factory set limit thermostat (Klixon) attached to the return bend of the coil on the right end of the
freezer to regulate the operation of the evaporator fans. If selected by the customer, the lights may be controlled by a second limit thermostat.
Cases utilizing electronic controls may utilize a coil temperature sensor to control operation of the fans and lights instead of a limit thermostat.
IMPORTANT! OPERATION OF THE LIMIT THERMOSTATS CAUSES THE EVAPORATOR FANS TO REMAIN OFF UNTIL THE
COMPRESSOR IS OPERATING AND THE COIL TEMPERATURE IS BROUGHT BELOW THE THERMOSTAT CUT-IN SETTING (+5°F ).
SUPERHEAT MUST BE SET CORRECTLY BY THE INSTALLING CONTRACTOR FOR PROPER THERMOSTAT OPERATION.
When the freezer first operates, the fans and lights may cycle off and on a few times until coil temperature is below +5°F. The superheat must
be set for proper operation.
Electric defrost models have a high limit thermostat installed on the coil return bend, wired in series with the defrost heaters. This thermostat
opens when the temperature reaches 85°F.