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The E71R controller allows only off-cycle defrost by powering off the compressor. The E72R controller includes the following Defrost Method options:
• Off Cycle: powers off the compressor
• Electric: powers off the compressor and powers on a heating element
• Reverse Cycle: powers on the compressor and powers on a valve that reverses the cooling cycle to pump heat into the evaporator coil
Defrost heat and an optional evaporator fan are controlled by the second relay on the E72R.
When defrosting begins, the Defrost Duration timer starts counting down real time. Defrosting ends when one of the following occurs, depending on
your configuration:
• The Defrost Duration timer expires
• The control temperature increases to the Defrost Termination Temperature
• The evaporator temperature (evaporator sensor) rises to the Defrost Termination Temperature
• The optional defrost termination switch is closed
If evaporator or control sensor termination is enabled, defrosting can terminate before the Defrost Duration timer expires. In this case the timer serves
as a failsafe.
When defrost is terminated, the optional Drip Time delay starts counting down. If the E72R is being used, the defrost relay switches position: The defrost
heater is powered off or the reverse cycle solenoid returns to the cooling position, and the evaporator fan is powered on. The compressor is not powered on
until the Drip Time delay expires. If the E71R is being used, the compressor remains powered off during the drip time. This delay is used primarily with
electrical or reverse cycle defrost to allow water removal between terminating heat and powering on the compressor. When the Drip Time delay expires, the
Time to subsequent defrosts timer resets and begins counting down to the next defrost cycle.
With both the Time to subsequent defrosts timer and the Temperature Initiated Defrost Function enabled the appliance is protected against excessive ice
buildup, which may accumulate quickly in abnormally high humidity environments.
5.1.5 Alarms
If the controlled temperature exceeds an alarm threshold or a sensor circuit fails, the red alarm LEDs on the controller and optional display indicate the type
of fault that has occurred. Additionally, the optional display identifies a sensor failure. The table below shows faults and indications.
5.1.5.1 Temperature
If temperature alarms are enabled, four setpoints define the high and low temperature alarms for the cold and warm positions. Similar to the temperature
setpoint, the high temperature alarm threshold is interpolated across the adjustment range from the configured high temperature alarm cold and high
temperature alarm warm setpoints. The low temperature alarm threshold is interpolated from the low temperature alarm setpoints at the cold and warm
positions. The Temperature Alarm Differential prevents alarm cancellation until the control temperature returns past the alarm threshold by the amount of
the differential. A high temperature alarm remains on until the temperature decreases to less than the high temperature alarm minus the differential. A low
temperature alarm remains on until the temperature increases to more than the low temperature alarm plus the differential.
Type E7 EcoCool™ Electronic Temperature and Defrost Controllers
©2008 Invensys Controls All rights reserved.
DRAFT VERSION
Fault Display Red Alarm LED
Temperature Alarm Control sensor temperature Illuminated
Control Sensor Circuit Failure E1 Flashing
Evaporator Sensor Circuit Failure Alternates between E2 and the control sensor temperature Flashing
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