Unit installation

Operating
52 SCXF-SVX01K-EN
position. MWU will end when the zone temperature rises
above the MWU terminate setpoint.
Timed Override Activation - ICS™
This function is operational whenever the unit’s RTM
module is used as the zone temperature sensor source,
which can be set at the HI panel. When this function is
initiated by the push of the override button on the zone
sensor, the unit will switch to the occupied mode. Unit
operation (occupied mode) during timed override is
terminated by a signal fromTracer.
Timed Override Activation - Non-ICS
This function is active whenever the unit’s RTM module
board is selected as the zone temperature source, which
can be set at the human interface panel. When this
function is initiated by the push of the override button on
the zone sensor, the unit will switch to the occupied mode.
Automatic cancellation of the timed override mode occurs
after three hours of operation.
VAV Drive Max Output
This is a single-pole, double-throw relay rated at a
maximum voltage of 24 vac, two amps max.The relay
contacts of this relay switch when the unit goes from the
occupied mode to the unoccupied mode by means of the
unoccupied binary input, night setback zone sensor, or
Tracer Summit.The contacts will stay switched during the
unoccupied and morning warm-up mode.They will return
to the position shown on the unit wiring diagram when the
unit returns to the occupied mode.The intent of this binary
output is to signal theVAV boxes or other terminal devices
to go to a full open airflow position.
Occupied Sequence
All setpoints can be adjusted using the HI panel. Also,
cooling/heating setpoints can be adjusted in the zone, if
using one of the zone sensor options (BAYSENS020,
BAYSENS021airsickAYSENS108, BAYSENS110,
BAYSENS019, or BAYSENS074). For a complete list of unit
setpoint default values and ranges, see the IntelliPak™
Self-Contained Programming Guide, PKG-SVP01B-EN.
Occupied Zone Temperature - Cooling
The unit transitions from unoccupied to occupied when
the occupied/unoccupied input on the RTM is open for
more than five seconds after having been closed.This
input can be received fromTracer Summit, the remote
NSB zone sensor, the timed override function, or a field
supplied contact. Dependent on unit options and the HI
programming, the following sequence will occur:
• The unit will begin MWU and then switch to the
occupied mode after the MWU setpoint is met.
• Purge will be enabled byTracer Summit.Then Tracer
Summit
will enable the occupied mode.
• The unit will switch from unoccupied to occupied
control
immediately.
Upon entering occupied mode, the occupied/unoccupied
relay
will de-energize.
Zone Temperature Control (Unit Model
Number Digit9=4or5)
A zone sensor located directly in the space sends input to
the RTM while the CV unit is in occupied cooling mode.
When the unit is in occupied cooling, the RTM controls the
zone temperature within the cooling setpoint deadband by
modulating the economizer option and/or staging
mechanical cooling on and off as required.
Supply Air Temperature Control (Unit Model
Number Digit9=1,2,3,or6)
When the VAV unit is in occupied cooling, the RTM
controls the supply air temperature to the specified supply
air cooling setpoint by modulating the economizer option
and/or staging mechanical cooling on and off as required.
The changeover relay contacts (field supplied) must be
open on units with hydronic heat for cooling to operate.
Cooling
Upon entering occupied mode, the RTM receives an input
from either the HI, RHI,Tracer Summit, or the GBAS to start
the supply fan.The RTM supply fan contacts close and
energize the supply fan contactor. When the supply fan
starts, the fan proving switch closes, signaling the RTM
that airflow is established.The VFD will ramp the fan, and/
or the airside economizer dampers will open to the user-
defined minimum position.
When a cooling request is sent to the RTM from the zone
sensor, the RTM evaluates the system operating
conditions using the supply air and outdoor temperature
input before sending the request to the MCM for
mechanical cooling. If outdoor conditions (temperature
and humidity) are suitable or the EWT is within specified
setpoints, the RTM will attempt to use “free cooling”
without using any compressors.The RTM will use either
the airside or waterside economizer option.When outdoor
air conditions are not suitable, only mechanical cooling
will function and outside air dampers will remain at their
minimum position. If the unit does not have an
economizer, mechanical cooling will operate to satisfy
cooling requirements.
Units With Economizer
If the entering condenser water temperature (units with a
WSE) or the outside air enthalpy (units with an ASE) is
appropriate to use “free cooling,” the economizer will
attempt to satisfy the cooling zone temperature setpoint.
Note: When using an ASE with economizer enabled, O/A
temperature enable can be used instead of
comparative enthalpy if the O/A temperature falls
below the economizer setpoint.
Then compressors will stage on as necessary to maintain
supply air temperature setpoint, which is user-defined at
the HI. Minimum on/off timing of compressors prevents
rapid cycling.