EZT-570S User Manual
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5.7 Defrost
Settings
These settings will be available on chambers equipped with defrost. This option is typically provided
on systems that must operate at low temperatures for extended periods of time or where frequent
entry into the chamber is required. It is used to periodically warm the refrigeration coils and remove
the normal accumulation of ice that occurs when running at low temperatures.
Moisture in the air is naturally attracted to the cold surface of the refrigeration coils in the chamber.
This moisture freezes to the surface of the coil over time and can eventually cover the entire surface.
This will render the coil useless and block all airflow in the chamber. In chambers that run through
high and low temperature cycles, the moisture does not accumulate to a detrimental level, but in
chambers that run at low temperatures for days or weeks at a time, this can be a problem.
Defrost is a means of warming the refrigeration coils to melt the ice, while minimizing the rise in
temperature of product within the chamber. When defrost is enabled, the air circulators shut down
and the hot-gas solenoid opens. The hot gas flows through the refrigeration coil and melts the ice.
Once the coil reaches a preset temperature limit, typically 10°C (50°F), defrost terminates. The
refrigeration system then precools the coil prior to turning on the air circulators. This further prevents
the warming of the chamber’s contents.
Defrost can be set to run automatically or under manual control through the use of an event. When
auto mode is selected, the EZT-570S will monitor the conditions of operation and automatically start
defrost based on the parameters the user has entered.
Figure 5-8 Defrost Settings
Defrost Delay:
Time in minutes between defrosts when auto mode is enabled. This is based on
Individual operating conditions. It may take some analysis to determine how long
your chamber can run before defrost is required.
Temperature SP:
Temperature below which defrost is enabled when in auto mode and after the
defrost delay, defrost will be activated. If at any time the chamber temperature
rises above the set point temperature, the delay timer will be reset and the
countdown will begin anew the next time the chamber temperature drops below
the set point.
This prevents defrost from starting at temperatures above which ice does not
form on the cooling coils.
Summary of Contents for EZT-570S
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