Sensor setup
The SN1 cooling temperature sensor monitors and controls the temperature in the refrigerated
space. Temperature-termination defrost applications and the adaptive defrost feature require a
SN2 defrost termination sensor mounted on the evaporator coil.
The controller can use two types of sensors. In North America, all standard MR5 controller models
ship with two A99B-type temperature sensors. In Europe, you can use the TS-6340 negative
temperature coefficient sensor (NTC). The SN1 and SN2 sensors are set up independently; SN1 and
SN2 do not have to be the same sensor type.
SN3 is an additional sensor. You can use an NTC or PTC type sensor as your SN3 sensor. You can
use the SN3 in the following ways:
Case temperature measurement
The controller averages the SN1 and SN3 temperatures.
Defrost termination temperature measurement
The controller averages the SN2 and SN3 temperatures.
Note:
When the controller calculates the temperature, it averages the two temperatures based
on the SN3 weight.
To set up the sensors on a controller, select the sensor type and the sensor offset on the system
setup screens. You can use the sensor offset to offset the sensed temperature, -3°C to 3°C or -5°F to
5°F. For example, if you apply a -3°F offset, the actual sensed value of 30°F displays and controls as
27°F.
QREV and PSHC setup
The controller can monitor and control an optional PENN
®
QREV and PSHC. The QREV is a
proportional control expansion valve that uses microelectromechanical system (MEMS) microvalve
technology to provide precise flow control for HVAC and refrigeration applications. The PSHC
controls the QREV performance. If the refrigeration system uses a QREV and PSHC, you can monitor
the QREV status, adjust the superheat setpoint, and change the refrigerant type on the PSHC to
match the refrigeration system’s refrigerant type. The QREV and PSHC status screens display the
following information:
• Superheat
• Evaporator outlet temperature
• Evaporator outlet pressure
• Current valve state
• PSHC firmware version
Evaporator fan control
Evaporator fan behavior depends on the following conditions:
• Whether the system’s mode of operation is refrigeration or defrost
• The selected evaporator setup options on the refrigeration and defrost setup screens
Evaporator fan operation in refrigeration mode
In normal refrigeration mode, you can set the evaporator fan to run continuously or to cycle on and
off with the compressor.
Evaporator fan operation in defrost mode
The evaporator fan drip-time delay and evaporator fan time delay settings affect the behavior
of the evaporator fan in defrost mode and post-defrost mode. You can set up the post-defrost
MR5 Series Panel Mount Case Controller Technical Bulletin
50
Discontinued
