Table of Contents
Energy Wheel Sequence of
Operation
Optional Economizer
• Stop Wheel: When economizer mode is enabled
and there is a signal for cooling, the wheel will
stop rotating to allow free cooling.
• Modulate Wheel: When economizer mode is
enabled and there is a signal for cooling, the
wheel VFD modulates wheel speed to maintain
the discharge temperature set point.
The economizer will be locked out when: the outside
air is <40°F (- 2°F hysteresis, adjustable); the unit is
operating in dehumidification mode; or there is a call
for heating.
Optional Frost Control -
The DDC controller will output
a signal when wheel frosting is occurring which is
determined by a temperature set point (OA <5°F –
2°F hysterisis, adjustable) and wheel pressure drop
increase.
• Preheat: When frosting is occurring, the
preheater is energized to defrost the wheel. Once
the pressure drop decreases below the set point,
the preheater is de-energized.
• Timed Exhaust: When frosting is occurring, the
supply blower is cycled off along with the heat
pump module for 10 minutes. The exhaust blower
shall continue to run allowing the warm exhaust
air to defrost the wheel. After the 10 minute cycle,
the supply fan and heat pump are re-energized to
continue normal operation.
Alarms Indication -
DDC shall have one digital output
for remote indication of an alarm condition. Possible
alarms include:
• Dirty Filter Alarm: If the outside air or return air
filter differential pressure rises above the switch
set point (adjustable), the differential pressure
switch shall signal the DDC to activate an alarm.
• Wheel Rotation Alarm: Monitors wheel rotation,
and sends a signal to controller (after a 15
second time delay with no rotation) that signals
the DDC to activate an alarm.
• Supply and Exhaust Air Alarm: DDC monitors
proving switch on each blower and displays an
alarm in case of blower failure.
• Dirty Wheel Alarm: DDC monitors pressure
across the wheel and sends an alarm in the case
of an increased pressure drop.
• DX Alarm: DDC monitors the refrigerant pressure
and shuts off refrigeration circuit in the case of
high or low refrigerant pressure.
• Temperature Sensor Alarm: DDC will send an
alarm in the case of a failed air temperature
sensor.
• Heat Pump Alarm: The UPM board controlling the
heat pump module will send an error signal to the
DDC which will then output a non-fatal, generic
alarm message.
Optional Accessories
The following accessories can be ordered with the
unit to expand the functionality or usability of the
controller.
• Room Temperature Sensor (TS): The room
temperature sensor is a field mounted sensor
that can provide a real-time temperature of the
space being served. The user will input a desired
room temperature setting, and the controller will
adjust the discharge temperature of the unit to
compensate for changes in room temperature.
• Room Dehumidistat (S8): The room dehumidistat
is a field mounted sensor that can monitor the
relative humidity (RH) of the space. If the RH
exceeds 60% RH, the dehumidistat will send
a digital signal to the controller to decrease
the after-cooling coil temperature. The DDC
will control the cooling type to achieve the
lower after-coil temperature until the space
dehumidistat is satisfied.
• BMS Interfacing: A BMS serial card is provided
with the controller for field interfacing with a
building management system. Each card is
sent out with the default parameters, and the
controls contractor must change the appropriate
addresses to match the BMS settings.
• DDC Remote Interface: An interface panel that
can be wired to the main controller for remote
adjustments of set points.
Model RT Energy Recovery Unit
23
Chapters
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