52
CNT-SVX05A-EN
Sequence of operation
Daytime warm-up
The daytime warm-up sequence is only available when the air handling unit has
heating capacity (hydronic or steam) and Tracer AH.540 is configured for:
• constant volume discharge air temperature control
• variable air volume control.
A communicated or wired space temperature is required for the Tracer AH.540
to initiate daytime warm-up.
Daytime warm-up forces the controller into heating when the space
temperature is below the effective heating setpoint by a temperature that is
more than the configured daytime warm-up enable differential. This initiated
sequence of operation coordinates the controller's heat/cool to heating, as well
as communicating the controller's application mode of operation to the duct
system for changeover.
Daytime warm-up start setpoint
is a configurable temperature below the
effective space heating setpoint. When the space temperature drops below the
start setpoint the daytime warm-up function is initiated by the controller.
Daytime warm-up stop 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.
Cooldown
The controller configured for constant volume space temperature control closes
the outdoor air damper (when present) at every transition from unoccupied to
occupied mode when the space temperature is 3ºF or more above the cooling
setpoint.
The damper remains closed during cooldown until the space temperature is
within 2ºF of the effective cooling setpoint. The damper normally is closed
during:
• anytime the supply fan is off
• warm-up/cooldown mode
• unoccupied mode
• certain diagnostic conditions
• low ambient damper lockout.
Filter status
The controller’s filter status is based on the supply fan’s cumulative run hours.
The controller compares the fan run time against an adjustable fan run hours
limit (maintenance required setpoint time, stored in the controller) and
recommends unit maintenance as required. The
Maintenance Required
diagnostic is informational only. Its state does not affect unit operation.
Use the Rover™ service tool to edit the Maintenance Required setpoint time.
When the setpoint limit is exceeded, the controller generates a
Maintenance
Required
diagnostic. To disable the diagnostic feature, set the maintenance
required setpoint time to zero.
You can use Rover service tool or Tracer Summit
™
to clear the
Maintenance
Required
diagnostic. When the diagnostic is cleared, the controller resets the
fan run time to zero and resumes accumulating fan run hours.
Freeze avoidance
Freeze avoidance is used as low ambient temperature protection and is only
