KR Electrical Defrost Unit Coolers (PN E108318_S) 30
9.3
DUAL SPEED MOTOR SEQUENCE OF OPERATION –
KR coils uses Dual Speed EC motors for fans used in DOE applications with the default being
the high speed and the second speed set as the minimum speed. Fans will be in Min speed/Full
speed or Off in scenarios below:
Minimum speed
•
When the room temperature or the refrigeration setpoint is met, the fan will operate at half
speed.
Full Speed
•
When the room temperature or refrigeration setpoint Is not met and the fan will run at full
speed.
Fan off
•
For EL/Gas defrost evaporators, during defrost fans will turn off.
A field control option is available for this motor to run at minimum speed and another option is
available for an installed room thermostat to operate this as a dual speed motor. When using the
installed room thermostat option, do not use the same thermostat to control the LLSV.
When using an installed thermostat, the SPDT switch of the thermostat will open when the room
temperature is above the setpoint and will not supply voltage through the control harness to motor.
When the room temperature is met, the SPDT switch of the thermostat will close and send the
voltage through the control harness and make motor to run at minimum speed.
When using the field controller, the motor low speed is controlled through an output, the output may
energize or de-energized based on room temperature input. Control harness should get voltage
only when the controller energized or de-energized the connected output.
When using the field-installed thermostat, the same concept of installed thermostat will be
applicable.
Wiring Connections –
Dual Speed motors will have three wires - Black, White, and Red. Black and white wires will
be always wired to terminal pin 7 and 4 for fan power. The red wire, which is named as control
harness, is connected to terminal 8. If the motor gets the supply through the control harness, it will
run in minimum speed.
9.4
VARIABLE SPEED MOTOR SEQUENCE OF OPERATION
Variable speed motor need 0-10V signal from filed, 0-10V signal wires will be connected to terminal
allotted in the Evaporator panel (Terminals 5 and 6). 0V being the high speed, 1475 RPM and 10V
being minimum speed of 400 RPM. Speed varies based on the analog signal received by motor.
9.5
VARIABLE SPEED MOTOR WITH SYSTEM 450 – SEQUENCE OF OPERATION
An installed System 450 C450CPN-4 controller will be utilized to supply a 0-10V signal to the
variable speed motor. Temperature sensor installed in the evaporator and wired to the System
450 control module will be utilized to measure the box temperature.
SYSTEM 450 PARAMETERS –
Set Point (SP) – is the target value that the control system drives toward. Set point at which
Fan motor will run at full speed. – Target Box Temperature
End Point (EP) – is the maximum deviation from the target value. Setpoint at which Fan motors
will run at Minimum speed – Target Box Temperature – 5°F
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