Dehumidification; Occupied And Unoccupied Mode Dehumidification - Trane Tracer AH540 Setup And Operation

Chapter 4 Sequence of operation
68
stage Off until the compressor minimum On time has expired (see
Table 39 on page 77).
Neglecting to remove or disable the electromechanical timers will cause
the compressor operation to lose coordination with the controller com-
pressor staging control, and will result in poor control performance.

Dehumidification

This sequence applies only to space temperature control.
The Tracer AH540/541 controller provides both occupied and unoccupied
dehumidification control when cooling and reheat capacity is available.
The dehumidification control sequence is allowed on unit configurations
with hydronic or DX cooling and hydronic or electric reheat.
Both occupied and unoccupied space humidity setpoints are provided as
well as setpoint offset values (10% default) to terminate dehumidification
mode. To disable occupied space dehumidification, set the Occupied Space
RH setpoint to 0%. Likewise, to disable unoccupied space dehumidifica-
tion, set the Unoccupied Space RH setpoint to 0%. Use the Rover service
tool to edit these setpoints.
Space dehumidification requires a space relative humidity sensor input
hard-wired to the universal analog input IN13 or a communicated RH
value. If both a hard-wired relative humidity sensor and a communicated
RH value is present, the communicated value will be used for dehumidifi-
cation control.

Occupied and unoccupied mode dehumidification

When the space relative humidity is greater than the Occupied Space RH
Setpoint, dehumidification control is initiated. The dehumidification con-
trol mode will remain active until space relative humidity is less than the
Occupied Space RH Setpoint minus Occupied Space RH Offset value. The
controller will automatically revert back to occupied or occupied standby
space temperature control.
When in unoccupied mode and the space relative humidity is greater than
the Unoccupied Space RH Setpoint, dehumidification is initiated until
space relative humidity is less then the Unoccupied Space RH Setpoint
minus Unoccupied Space RH Offset value. The controller will automati-
cally revert back to unoccupied space temperature control.
Space temperature and relative humidity are both controlled when dehu-
midification is active. Cooling capacity is modulated or staged to reduce
space humidity, while heating capacity is modulated or staged to control
space temperature. Hydronic cooling capacity is modulated (increased
and decreased) to offset the relative humidity load in the space. DX cool-
ing capacity operates as a limit control and is only allowed to stage up
(increase) to maintain or decrease the relative humidity in the space.
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