Fan Operation During Discharge; Fan Operation During Smoke Event; Digital Inputs For Monitoring; Water Differential Pressure Switch (Dps) - Carrier Omnizone 50BVC Installation, Start-Up, Service And Controls Operation And Troubleshooting

The supply and return air fan speeds are modulated by inde-
pendent PID loops to maintain independent static pressure set
points; the factory-provided duct static pressure sensor is re-
quired as input (connected to UI 11 for supply and IN-10 for re-
turn) on the I/O Flex 6126 controller and the I/O Flex EX8160
expander, for the VFD blower option. Units do not allow for
mounting of the Return Fan VFD inside the equipment and re-
quire the VFD equipment to be mounted close to the unit. An
inside wall in the mechanical room close to the unit is typically
used for mounting an external VFD. See Table 28 for VFD fac-
tory default settings.
SUPPLY AND RETURN FAN OPERATION — When the
unit control is set for occupied operation the fan will run
continuously as the default behavior. If the return fan is en-
abled, it will follow the operation of the supply fan mode
which may be modified to cycle only during mechanical op-
eration. During unoccupied operation the fan will only cycle
during a call to maintain a cooling set point.
FAN OPERATION DURING DISCHARGE (SUPPLY AIR
TEMPERATURE) AIR CONTROL (DAC) — For DAC ap-
plications, the fan's speed is calculated as a demand percent
calculated based on the PID static pressure sensor value and
the static pressure set point.
If static pressure reset strategies are utilized the minimum
fan speed recommended is 40% of nominal CFM. If the fan de-
mand is less than 40% of nominal CFM (20% for the return
fan) the PID loop will be disregarded and the fan will run at the
minimum value.
Units configured for discharge air control will run only
when the controller is in occupancy mode.
VFD CONTROL — The following applies for VFD Control:
• Variable frequency drive fan control requires a static
pressure measurement. A duct static pressure sensor is
factory supplied to be installed in the field.
• The static pressure sensor uses inches of water column as
the unit of measure.
• The static pressure sensor is configured for UI-11 port of
the I/O Flex 6126 controller for the supply duct and IN-10
for the return air duct.
• The static pressure set point is user configurable and is
used by the static pressure PID control.
• The minimum VFD fan speed is user configurable and is
set during the test and balance phase of the commission-
ing phase.
• A high static pressure alarm will be generated for a static
pressure exceeding the maximum static pressure trip
point for a minimum of 10 minutes.
• The static pressure sensor will be range-validated and a sen-
sor failure alarm will be generated for a missing sensor.
• The VFD output may be switched to a constant value for
a smoke event if enabled.
FAN OPERATION DURING SMOKE EVENT — The speed
of the fan during a smoke event is user configurable for VFD en-
abled units (defaults to 100%).
FAN HISTORY STATISTICS — The controller will collect
fan history statistics and sum the total number of fan start
events that occurred in the preceding 1-hour period. The fan
history may be reset by the user. Fan history reset may be per-
formed locally at the unit with a BACview terminal.
Digital Inputs for Monitoring —
ware may be configured to provide digital inputs for monitor-
ing unit faults and alarms. The equipment integrator must con-
figure the input for the appropriate installed option and desired
The controller soft-
46
function. The functional options may be configured via a local
terminal or building automation system.
FILTER STATUS (DFS) — The I/O Flex 6126 controller
has the option of providing a filter alarm for indicating that
the filter needs servicing. The filter-status service option may
be implemented with hardware or with fan run time. The filter
switch hardware is connected directly to IN-4 on the I/O Flex
EX8160 expander with a contact closure indicating a service
event.
The following applies to the filter status:
• The filter status (replacement) may be configured for
accumulated running time.
• The total fan run time prior to filter service is user con-
figurable, factory default 2000 hrs.
• The filter timer may be reset upon the filter being serviced.
WATER DIFFERENTIAL
(DPS) — The differential pressure switch is applied to a unit
for which the flow of water through the heat exchange must
be confirmed prior to the unit operating. The differential
pressure switch hardware is connected directly to IN-6.
In addition, the following applies to the DPS option:
• An alarm notification is set if the DPS is asserted True
(no flow condition).
• A DPS alarm will terminate compressor operation.
• Three DPS events will hard lockout the unit.
• The DPS hard lockout condition which will keep the unit
off can be cleared by a reset via the BACview tool.
• A sum of all DPS events will be logged for a 1-hour period.
SMOKE DETECTOR STATUS (SDS) — The unit may be
set up to receive a smoke event via a contact closure. The
smoke detector input is available for field wiring on IN-1 of
the I/O Flex EX8160 expander.
The response to a smoke event must be determined by safe-
ty regulations and jurisdiction of the local governing body. The
smoke detector response must be enabled and set up upon sys-
tem start-up. The default behavior for a smoke event will termi-
nate the operation of the unit (fan and compressor).
The unit may be configured for operation during a smoke
event for specific safety applications. Variable Frequency
Drive configured units can be configured for a specific fan
speed during a smoke event.
A smoke detector contact closure on IN-1 will produce a
Smoke Alert.
COMPRESSOR STATUS — The unit is equipped with com-
pressor status current transducers and Input Expansion Mod-
ules (IEM) and will verify that the compressor stages are run-
ning by monitoring the status of the current switches. If the
compressor fails (no current flow) an individual alarm per com-
pressor stage will occur.
The controller will identify the compressor operating in the
following three modes:
• Auto (no alarm)
• Hand mode
• Failed
Cooling Operation —
supply air temperature and set point by staging the compres-
sor(s). To prevent short-cycling, there is a 10-minute delay be-
tween compressor stages. Additionally, there will be a 3-minute
delay (adjustable) to prove water flow prior to Compressor 1
operation when the unit is first powered on. The compressor
will run subject to internal safeties and controls provided by the
UPM board.
PRESSURE SWITCH
The controller will maintain the