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VFD CONTROL
The following applies for VFD Control:
• Variable frequency drive fan control requires a static pres-
sure 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 commissioning
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
sensor 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 enabled 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 performed locally at the unit with a BACview terminal.
Digital Inputs for Monitoring
The controller software may be configured to provide digital in-
puts for monitoring unit faults and alarms. The equipment integra-
tor must configure the input for the appropriate installed option
and desired 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 accu-
mulated running time.
• The total fan run time prior to filter service is user configu-
rable, factory default 2000 hrs.
• The filter timer may be reset upon the filter being serviced.
WATER DIFFERENTIAL PRESSURE SWITCH (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 clo-
sure. 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 safety regu-
lations and jurisdiction of the local governing body. The smoke
detector response must be enabled and set up upon system start-
up. The default behavior for a smoke event will terminate the op-
eration of the unit (fan and compressor).
The unit may be configured for operation during a smoke event
for specific safety applications. Variable Frequency Drive config-
ured 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 compressor status current transducers
and Input Expansion Modules (IEM) and will verify that the com-
pressor stages are running by monitoring the status of the current
switches. If the compressor fails (no current flow) an individual
alarm per compressor stage will occur.
The controller will identify the compressor operating in the fol-
lowing three modes:
• Auto (no alarm)
• Hand mode
• Failed
Cooling Operation
The controller will maintain the supply air temperature and set
point by staging the compressor(s). To prevent short-cycling, there
is a 10-minute delay between compressor stages. Additionally,
there will be a 3-minute delay (adjustable) to prove water flow pri-
or to Compressor 1 operation when the unit is first powered on.
The compressor will run subject to internal safeties and controls
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