FAXA-SVX01B-EN
67
Operation
sequence of
operation
2
Unoccupied Sequence
When the return air damper option is
installed and a request for unoccupied
operation is received, the fan and cooling/
heating capacity cycle in a recirculating
mode to maintain zone requirements.
See below for a detailed description of
the operating modes.
If no return air damper is installed, the fan
stops and the OA damper closes in
unoccupied mode.
Drying Mode
During unoccupied mode (with return air
damper option installed), the unit enters
the drying mode when the zone RH
exceeds the unoccupied zone RH
setpoint. In the drying mode, capacity
cycles to maintain the supply air drying
(dew point) setpoint. The SA drying
setpoint can be reset down based on
zone relative humidity conditions and will
be based on the unoccupied zone RH
setpoint.
Supply air reheat functions are active to
maintain the supply air reheat setpoint.
Supply air reheat reset functions are
active and reset based on unoccupied
zone setpoints. Exhaust fan operation
control will cycle off during unoccupied
modes unless unoccupied economizer
operations are active.
Cooling Mode
During unoccupied cooling mode, the fan,
economizer, and mechanical cooling cycle
to control zone temperature. Economizer
functions will enable when the difference
in the enthalpy of the OA and zone is
adequate. Mechanical cooling
supplements economizer capacity as
required.
Heating Mode
During unoccupied heating mode, fan
and heating capacity cycle to maintain
the unoccupied zone heating setpoint.
Supply Air Temp Control (No
Dehumidification) Unit
1
Occupied Sequence
During occupied mode, the primary
function of the unit is to provide
ventilation air to the space. Upon entering
the occupied mode, the outside air
damper opens and the supply air fan
starts.
Cooling Sequence
The unit stages cooling capacity to
maintain the supply air cooling setpoint.
The supply air cooling setpoint can be
reset down based on HI selectable
parameters (OA sensor, zone sensor if
installed).
Heating Sequence
The unit stages heating capacity to
maintain the supply air heating setpoint.
The supply air heating setpoint can be
reset up based on HI selectable
parameters (OA sensor, zone sensor if
installed). The supply air heating setpoint
must be lower than the supply air cooling
setpoint.
2
Unoccupied Sequence
In unoccupied mode, the fan stops and
the OA damper closes.
Zone Temp Control (No
Dehumidification) Unit
1
Occupied Sequence
During occupied mode, the primary
function of the unit is to provide
ventilation air to the space. Upon entering
the occupied mode, the outside air
damper opens and the supply air fan
starts.
Cooling Sequence
The unit stages cooling capacity to
maintain the supply air cooling setpoint.
The supply air cooling setpoint can be
reset down based on HI selectable
parameters (OA sensor, zone sensor if
installed).
Heating Sequence
The unit stages heating capacity to
maintain the supply air heating setpoint.
The supply air heating setpoint can be
reset up based on HI selectable
parameters (OA sensor, zone sensor if
installed). The supply air heating setpoint
must be lower than the supply air cooling
setpoint.
2
Unoccupied Sequence
In unoccupied mode, the fan stops and
the OA damper closes.
Control Sequences of
Operation
Morning Warmup
This feature is available on all types of
factory-installed heat units and on units
with no heat. This function may still be
selected to support systems with heat
sources not provided by the fresh air unit.
At the conclusion of unoccupied mode,
the selected zone is heated to the user-
defined morning warmup setpoint. The
unit is then released to occupied mode.
There are two types of morning warmup:
full capacity or cycling capacity.
• Full capacity morning warmup (MWU)
Full capacity morning warmup uses full
heating capacity to heat the zone as
quickly as possible. Full heating capacity
is provided until the morning warmup
setpoint is met. At this point, the unit is
released to daytime mode.
• Cycling capacity morning warmup
(MWU)
Cycling capacity morning warmup
provides gradual heating to overcome
“building sink” as the zone is heated.
Normal zone temperature control with
varying capacity raises the zone
temperature to the MWU zone
temperature setpoint. Cycling capacity
MWU will operate until MWU setpoint is
reached or for 60 minutes. Then the unit
switches to occupied mode. Cooling will
suspend until building load conditions
exceed the MWU setpoint of 3°F (1.7°C),
which is field adjustable.
Ventilation Override (VOM) Option
The user can customize up to five
different override sequences for
purposes of ventilation override control. If
more than one VOM sequence is
requested, the sequence with the highest
priority initiates first. Priority schedule is
that sequence “A” (unit off) is first, with
sequence “E” (purge sequence) last.