Low Ambient Damper Lockout; Exhaust Fan Operation - Trane Tracer AH540 Setup And Operation

Table 23. Relationship between outdoor temperature sensors and damper position
Outdoor air temperature
No or invalid outdoor air
temperature
Failed outdoor air sensor
Outdoor air temperature
less than the low ambient
damper lockout setpoint
Outdoor air temperature
present and economizing
feasible
Outdoor air temperature
present and economizing
2
not feasible
1 The low ambient damper lockout setpoint is a configurable temperature setpoint used to close the outdoor air damper, regard-
less of occupancy, when extreme outdoor air temperatures are present.
2 The Tracer AH540/541 controller disables economizing if the mixed-air temperature sensor is not present or is not valid.
CNT-SVX05B-EN
Occupied or
Occupied bypass
Open to occupied mini-
mum position
Open to occupied mini-
mum position
Closed
1
Economizing, damper
controlled between occu-
pied minimum position
and 100%
Open to occupied mini-
mum position

Low ambient damper lockout

The controller closes the outdoor air damper during any heating, cooling,
or economizer mode of operation or occupancy when extreme outdoor air
temperatures exist. This condition disables outdoor air damper ventila-
tion and economizing functions, but low ambient damper lockout does not
affect other unit operations.
The outdoor air temperature must rise 9°F (5°C) above the low ambient
damper lockout setpoint before economizing and ventilation become pos-
sible again.

Exhaust fan operation

This sequence applies to both space temperature control and discharge
air temperature control.
The exhaust fan/damper is coordinated with the unit supply fan and out-
door damper operation. The exhaust output is energized only when the
unit supply fan is operating and the outdoor damper position is greater
than or equal to the configurable exhaust fan start setpoint. The exhaust
fan output is disabled when the outdoor air damper position drops 10%
(configurable) below the exhaust fan start setpoint. If the enable point is
less than 10% (configurable), the unit turns On at the start setpoint and
Off at zero.
Outdoor air damper
Occupied standby
Open to occupied standby
minimum position
Open to occupied standby
minimum position
Closed
Economizing, damper
controlled between occu-
pied standby minimum
position and 100%
Open to occupied standby
minimum position
Exhaust fan operation
Unoccupied
Closed
Closed
Closed
Open and economizing
during unit operation, oth-
erwise closed
Closed
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