Zero Zone 3RMCC30WA, Руководство по установке и эксплуатации

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DEFROSTING
LOW TEMP (CONT.)
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, light and anti-sweat heater limit
thermostats (Klixons) will close, starting the fans, lights and anti-sweat heaters.
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.
(
Figure 33 and Figure 34 on page 41 ).
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 locality. 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
Each freezer has factory set limit thermostats (Klixons) attached to the return bends of the coil on the right end of the freezer to
regulate the operation of the evaporator fans and anti-sweat door heaters. A limit thermostat is optional for the light circuit. When a limit
thermostat is provided in the lighting circuit, the lights will be off during defrost.
IMPORTANT! OPERATION OF THE LIMIT THERMOSTATS CAUSES THE EVAPORATOR FANS, FREEZER LIGHTS, AND ANTI-SWEAT
DOOR HEATERS 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.
The 30" door 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.
40 • Defrosting - Low Temp