Cool-Down; Space Temperature Control: Cool-Down; Discharge Air Temperature Control: Cool-Down - Trane Tracer AH540 Setup And Operation

Cool-down

below the start setpoint, the daytime warm-up function is initiated by the
controller.
The daytime warm-up terminate setpoint is a configurable temperature
above the start setpoint. When the space temperature rises above the
stop setpoint, the warm-up function is terminated by the controller.
Unlike morning warm-up, the outdoor air damper is at the configured
minimum position or at the communicated minimum damper position
according to the effective occupancy.
Cool-down
In cool-down operation the controller closes the outdoor air damper elimi-
nating any additional cooling load due to warm outdoor temperatures.
Normally the outdoor air damper is closed in this mode of operation and
hydronic or mechanical cooling is provided to cool-down the space. How-
ever if the outdoor air temperature is suitable economizer cooling is
allowed.
The Tracer AH540/541 controller operates this sequence according to the
configured control mode.

Space temperature control: Cool-down

If configured for space temperature control, the controller provides an
automatic cool-down function on a transition from unoccupied to occupied
or occupied standby mode of operation. Cool-down is initiated and the
outdoor air damper remains closed if space temperature is greater than
3ºF above the active cooling setpoint. As the space temperature decreases
below this threshold, the outdoor damper progressively opens toward the
minimum position setpoint. When the space temperature is within 2ºF of
the effective cooling setpoint, the outdoor damper will be at the occupied
or occupied-standby minimum position setpoint.
Cool-down can also be initiated by a building automation system with a
mode command of pre-cool (optimal-start). The controller will stay in the
pre-cool until the mode is removed by the system. For more details, see
Table 71 on page 101.
A heating-only air-handling-unit configuration, with no cooling capacity,
disables the automatic cool-down function. The outdoor air damper (if
present) will open to minimum position and provide economizing, if
enabled.

Discharge air temperature control: Cool-down

If configured for discharge air temperature control, the controller enters a
cool-down mode only when coordinated by a building automation system
(optimal-start). In cool-down, the controller's heat-cool mode is reported
as pre-cool. The controller will stay in the pre-cool until the mode is
removed by the automation system. For more details, see Table 72 on
page 103.
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