A52x Series Electronic Refrigeration Controller with Adaptive Defrost Technical Bulletin
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Date (day, month, and year)
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Automatic Daylight Saving Time change over.
Sensor Setup
The A52x Controller requires the Sn1 cooling temperature sensor to monitor and control the cooling temperature in
the refrigerated space. Temperature-termination defrost applications and the Adaptive Defrost feature requires
either a Sn2 defrost termination sensor or a HVBIN defrost termination switch mounted on the evaporator coil.
The A52x Controller can use two types of sensors. In North America, all standard A52x Controller models ship with
two A99B-type temperature sensors. In Europe, the TS-6340 Negative Temperature Sensor (NTC) is available for
use. The sensors are set up independently; Sn1 and Sn2 do not have to be the same sensor type.
To set up the sensors on an A52x Controller, select the sensor type and the sensor offset in the System Setup
screens. The sensor offset allows you to offset the sensed temperature -5C° to 5C° or -5F° to 5F°. For example, if
you apply a -3°F offset, the actual sensed value of 30°F displays and controls as 27°F.
Evaporator Fan Setup
Select either a single-speed evaporator fan or a two-speed evaporator fan. The HI-SPD relay controls single-speed
evaporator fans. The LO-SPD/AUX relay and the HI-SPD relay control two-speed EC evaporator fans. When you
control single-speed fans with the HI-SPD relay, the LO-SPD/AUX relay is available to control an auxiliary device.
QREV/PSHC Setup
The A52x Controller is designed to communicate with the Johnson Control/PENN Quick Response Expansion
Valve (QREV) and Precision Super Heat Controller (PSHC). If the refrigeration system uses a QREV/PSHC, you
can monitor the QREV status, adjust the superheat set point, and change the refrigerant type on the PSHC to
match the refrigeration system’s refrigerant type. The QREV/PSHC status screens display the superheat, the
evaporator outlet temperature and pressure, the current valve state, and the PSHC firmware version.
Evaporator Fan Control
Evaporator fan behavior depends on the following conditions:
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Whether the evaporator fan is one-speed or two-speed
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Whether the system’s mode of operation is refrigeration or defrost
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The selected evaporator set up options in the Refrigeration and Defrost setup screens
Evaporator Fan Operation in Refrigeration Mode
In normal refrigeration mode, you can set a single-speed evaporator fan to run continuously or to cycle on and off
with the compressor. See Figure 9 on page 12. You can set a two-speed evaporator fan to run continuously at high
speed. See Figure 10 on page 13. You can also cycle between low-speed and high-speed. See Figure 11 on
page 13.
