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Installation
Due to our policy of continuous product innovation, some specifications may change without notification.
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CONTROLLER
Economizer
The economizer function is used to modulate the outside air damper to cool the supply air temperature using outside air. The outside damper
modulates open based on the economizer demand in order to maintain the supply temperature set-point.
Economizer Availability: The economizer is available when the following conditions are met:
• Heating is not active; and
• Cooling is active; and
• The enable condition for the selected mode is met.
Economizer Modes: The user can select the economizer control method from the following options:
• Outside Dry Bulb: Economizing is allowed when the outside dry bulb is less than the economizer temperature enable set-point.
• Outside Enthalpy: Economizing is allowed when outside enthalpy is less than the economizer enthalpy set-point.
• Comparative Dry Bulb: Economizing is allowed when outside temperature is less than the space or return temperature.
• Comparative Enthalpy: Economizing is allowed when outside enthalpy is less than the space or return enthalpy.
• Fall Back: If enabled, the economizer control mode can revert to the previously available option during a sensor failure to continue econo-
mizing.
Energy Recovery
The heat wheel or flat plate heat exchanger face/bypass damper is controlled to maintain the supply temperature set-point.
Defrost: Energy recovery devices may require defrosting if the exhaust air temperature gets too cold. The following methods are available
depending on the type of energy recovery installed in the unit:
•
Modulating: Energy recovery output is reduced in order to maintain the exhaust air temperature above the defrost set-point.
• Fixed Capacity: The wheel will be cycled on and off to maintain an exhaust temperature above the defrost set-point. The wheel cycles on
for thirty (30) seconds then off for five (5) minutes.
Wheel Pressure Drop Control: Wheel supply and exhaust bypass dampers modulate to maintain a differential pressure set-point across the
wheel.
Heat Wheel Jog Function: Momentarily enables the wheel to expose a new section to the air stream.
Dehumidification
When dehumidification mode is active, the cooling device is controlled to maintain the cooling coil leaving air temperature set-point. Reheat
or Reheat Plus is controlled to maintain the supply temperature set-point.
This sequence does not apply to pool application units.
Availability: The following must occur to enable dehumidification mode:
• Humidification is not active; and
• The humidification/dehumidification mode switch delay has expired;
and
• Cooling is not locked out (except in the case of a regeneration unit);
and
• There is a call for dehumidification.
Sequences of Operation
