Dew Point - Initiation
Occupied dehumidification Dew Point control initiates when the following conditions exist:
• Space Dew Point is greater than the Space Dew Point Setpoint and
• Outdoor Air Dew Point is greater than the Outdoor Air Dew Point Setpoint
Unoccupied dehumidification Dew Point control initiates when:
• Space Dew Point is greater than the Space Dew Point Unoccupied Setpoint and
• Outdoor Air Dew Point is greater than the Outdoor Air Dew Point Setpoint and
• Space has been unoccupied for less than Unoccupied Dehumidification Timer and relative humidity
is greater than 65% or
• Space has been unoccupied for greater than or equal to Unoccupied Dehumidification Timer
The Unoccupied Dehumidification Timer is default to 12 hours. Setting the timer to 0 effectively disables
the timer and, unoccupied dehumidification initiates only according to Space and Outdoor Dew Point.
Relative Humidity - Initiation
Occupied dehumidification control initiates when the Space Humidity is greater than the Space
Dehumidification Setpoint. Unoccupied dehumidification control initiates when the Space Humidity is
greater than the Space Dehumidification Unoccupied Setpoint.
Operation
Compressors are controlled to manage the humidity latent load by staging up as needed to achieve a
Symbio™ 700 determined the target evaporator coil dew point, based on space conditions.
Space temperature is managed by modulating the hot gas reheat valve. The valve will not open until the
space temperature is below the space cooling setpoint minus 1.5°F and modulates to achieve the
Reheat Discharge Air Temperature Setpoint to maintain space temperature control.
Anytime during occupied modes of operation, if the space temperature falls 3°F below the cooling
setpoint or less than heating setpoint and the reheat valve is at a maximum position for 5 minutes,
dehumidification control terminates.
During unoccupied dehumidification, if the space temperature falls below 60°F and the reheat valve is at
maximum position for 5 minutes, dehumidification control terminates.
Dew Point - Termination
Occupied dehumidification Dew Point control terminates when:
• Calculated Space Dew Point is less than the Space Dew Point Setpoint minus the Dew Point
Setpoint Offset or
• Outdoor Air Dew Point is less than the Outdoor Air Dew Point Setpoint minus the Dew Point
Setpoint Offset
Unoccupied dehumidification Dew Point control terminates when:
• Space Dew Point is less than the Space Dew Point Unoccupied Setpoint – Dew Point Setpoint
Offset or
• Outdoor Air Dew Point is less than the Outdoor Air Dew Point Setpoint – Dew Point Setpoint Offset
or
• Space has been unoccupied for less than Unoccupied Dehumidification Timer and Space Relative
Humidity is less than 65% minus Space Dehumidification Setpoint Offset
Relative Humidity - Termination
Occupied modes of operation, Space Dehumidification control terminates when the Space Humidity is
less than the Space Dehumidification Setpoint minus the Space Dehumidification Setpoint Offset.
In unoccupied mode, Space Unoccupied Dehumidification control terminates when the Space Humidity is
less than the Space Dehumidification Unoccupied Setpoint minus the Space Dehumidification Setpoint
Offset.
Dehumidification Purge Cycle
During dehumidification, a 3–minute compressor cooling purge cycle initiates according to the Reheat
Purge Interval (120 minutes adjustable). The modulating hot gas reheat valve moves to a fixed position
and compressors go to full capacity.
Symbio 700 Controller Application Guide
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WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.