FAXA-SVX01B-EN
69
Operation
sequence of
operation
Timed Override Activation - Non-ICS
This function is active whenever the user
selects the unit’s RTM module board as
the zone temperature source (can be set
at the human interface panel). Initiate this
function by pressing the override button
on the zone sensor, which will switch the
unit to the occupied mode. Automatic
cancellation of the timed override mode
occurs after three hours of operation.
Low Ambient Compressor Lockout
This function will lock out the compressor
if the outdoor air temperature is below
the low ambient compressor lock-out
temperature setpoint when using a field-
installed outside air sensor. This setpoint
is adjustable at the human interface
panel. Compressors will lock out when
outdoor air temperature falls below that
selected temperature and will start again
when the temperature rises 5°F above
the setpoint.
Comparative Enthalpy Control of
Unoccupied Economizer Operation
An optional comparative enthalpy
system controls the economizer
operation and measures the temperature
and humidity of both return air and
outside air to determine which source
has lower enthalpy. This system allows
true comparison of outdoor air and return
air enthalpy by measurement of outdoor
and return air temperature and humidity.
The comparative enthalpy option should
always be ordered with a return air
damper.
Note: If the unit does not have compara-
tive enthalpy, the Packaged Fresh Air unit
compares outdoor air enthalpy with a
fixed reference enthalpy, set through the
human interface panel. If ordering the
reference enthalpy option, you should
also order a return air damper. Also,
either supply air dehumidification with
zone RH reference or zone dehumidifica-
tion with OA RH reference must be
ordered to utilize either comparative
enthalpy or reference enthalpy control.
Emergency Stop Input
A binary input is provided on the unit’s
RTM module board for installation of a
field-provided switch or contacts to
immediately shutdown all unit functions.
Total Energy Wheel with Occupancy
Control
The optional total energy wheel recovers
energy from the exhaust airstream and
preconditions the outdoor air. The total
energy wheel enables when the unit is in
occupied mode and the exhaust fan is
running. The wheel disables during
unoccupied mode or any time that the
exhaust fan is not running. This includes
the unoccupied economizer mode when
the wheel disables, but the exhaust fan
enables. The wheel also disables via a
factory-installed thermostat at any time a
frost condition occurs (default setpoint
12°F). This frost protection thermostat
utilizes a setpoint range of -30 to 100°F.
Total Energy Wheel with Dry-Bulb
Control
The optional total energy wheel recovers
energy from the exhaust airstream and
preconditions the outdoor air. The total
energy wheel enables when all of the
following are true:
• unit is in occupied mode
• exhaust fan is enabled
• outside air temperature is above the
upper limit setpoint (default setpoint
80°F) or below the lower limit setpoint
(default setpoint 45°F)
• outside air temperature is above the
frost protection setpoint (default
setpoint 12°F)
Always set the upper limit setpoint to the
anticipated return air dry-bulb tempera-
ture. Set the lower limit setpoint to 10°F
less than the unit supply air dry-bulb
setpoint. The wheel will disable during
unoccupied mode or when the exhaust
fan is not running. This includes the
unoccupied economizer mode when the
wheel will disable, but the exhaust fan will
enable. The wheel also disables via a
factory installed thermostat when a frost
condition occurs. This frost protection
thermostat utilizes a setpoint range of -30
to 100°F.