Low Ambient Damper Lockout; Exhaust Fan Operation - Trane LPC Install And Operation Instructions

Table O-SO-10. Relationship between outdoor temperature sensors & damper 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 ventilation
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 possible 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 outdoor
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
80
Operation
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.
The controller logic commands the
exhaust fan to be energized/de-energized
based on the target position of the
economizing damper. Because of device
stroke time, the state of the exhaust fan
may change before the economizing
damper reaches its target position.
If the exhaust fan start setpoint is set at or
lower than the outdoor air damper
minimum position, the exhaust fan will be
On continuously when the outdoor air
damper is at minimum position.
If the exhaust fan start setpoint is set
higher than the outdoor air damper
minimum position (minimum ventilation)
the exhaust fan will be Off during periods
of minimum ventilation. During econo-
mizer cooling operation the exhaust fan
start setpoint can be selected to compen-
sequence of
operation
sate for the increased outdoor ventilation.
The exhaust fan status binary input is
present to detect operation of a belt-
driven exhaust fan. An Exhaust Fan Air
Flow diagnostic is detected when the
control starts the exhaust fan and the
exhaust fan status binary input does not
indicate operation after two minutes. This
is an exhaust fan latching diagnostic and
discontinues exhaust operation until the
diagnostic is reset. All other control
functions continue to operate normally.
Electric heat operation
This sequence applies to both space
temperature control and discharge air
temperature control, with differences as
noted.
The Tracer AH540/541 supports two
methods of controlling staged electric
heat:
1. Staged electric heat using binary
outputs.
2. Staged electric heat using a sequencer
For details, see "Staged electric heat".
LPC-SVX01C-EN