Supply Fan Duct Pressure And Vav Control Group; Supply Fan Duct Pressure Control (Vav Only) - Carrier 48FP Controls Operation And Troubleshooting

DESCRIPTION
Set Dehumidification Set Point
("High Humidity Override")
NOTE: If Unit Type is VAV, unit must be configured for Occupied Heating Enabled (see Table 13, Configuring Heating).
HUMIDIFIER CONTROL — There are 2 types of Humidifi-
er control functions available with these units: Analog-output
control or Discrete-output control. Analog-output control is
used to control a proportional steam valve serving a steam grid
humidifier (field-supplied and -installed). Discrete-output is
used to control a single-stage humidifier with a spray pump
(field-supplied and -installed). See Table 34.
A humidifier system (control connects to PSIO2,
Channel 45) and a humidity sensor are required. The control
options module (available as a factory-installed option or field-
installed accessory on size 034-074 units and is standard on
078-104 units) is required for humidifier control.
Table 34 — Humidifier Control Definitions
ITEM
HUEN Humidifier Type Configuration
HUM Humidifier Position (Analog)
HUSN Humidity Sensor(s) Configuration
HUSP Humidity Set Point
HUSR Humidity Submaster Reference
RH Relative Humidity
Sequence of Operation (Analog-Output Device)
1. If the supply fan is off, the humidifier will be off.
2. If the Occupancy Schedule indicates Unoccupied
mode, the humidifier will be off.
3. When the humidity level at the sensor drops below the
set point, if the supply fan is ON and unit is in Occu-
pied mode, an output signal will open the steam valve
until the set point is satisfied.
4. When the humidity level at the sensor exceeds the set
point, the steam valve will be closed.
Sequence of Operation (Discrete-Output Device)
1. If the supply fan is off, then the humidifier will be off.
2. If the Occupancy Schedule indicates Unoccupied
mode, the humidifier will be off.
3. When the humidity level at the sensor drops below the
set point, the output signal will energize the spray
pump control until the set point is satisfied.
4. When the humidity level at the sensor exceeds the set
point, the spray pump control will be deenergized.
Configuration — To configure:
1. Identify the sensor type. Press
subfunction. Scroll down to HUSN. Press
and . If differential humidity sensors are installed,
ENTER
configuration should be set to 1. If a single humidity
sensor is installed (space or return air), configuration
should be set to 2.
2. Identify Humidifier control type. Press
the subfunction. Scroll down to HUEN. Configuration
can be set to 1 or 2. For analog applications, select 1.
For discrete applications, select type 2. Enable Data
Reset.
3. Set Humidity Set Point. Press
function. Scroll down to HUSP. The default is 40% rh
(relative humidity). The range is 0 to 100% rh.
Table 33 — Configuring Dehumidification and Reheat
HOW TO CONFIGURE AT HSIO
DEFINITION
to enter the
or
to enter
to enter the sub-
Algorithms
HUSR = PID function on (Demand term)
where (Demand term) = Humidity Set Point – Humidity
Supply Fan Duct Pressure and VAV Control
Group —
This group includes Duct Pressure Control (IGV/
VFD control), Supply Air Temperature (SAT) Reset from
Space Temperature, and SAT Reset from External Signal.
SUPPLY FAN DUCT PRESSURE CONTROL (VAV
Only) — The control will modulate control output to an Inlet
Guide Vane (IGV) option or a Variable Frequency Drive (VFD
option), in a VAV system, to maintain duct static pressure at
user-configured set point. See Table 35.
The following items are required for supply fan volume
control:
• IGV or VFD Option
1
• / .-in tubing (flame-retardant plenum duty)
4
• static pressure probe
Table 35 — Supply Fan Duct Pressure
Control Definitions
ITEM
DPEN Duct Pressure Control Option
DSPSR Duct Static Pressure Submaster Reference
SL Submaster Loop
SPSP Static Pressure Set Point
SR Submaster Reference Value
Sequence of Operation — The status of the supply fan is de-
termined. If the fan status is on, the control reads the duct static
pressure and calculates the Duct Static Pressure SR (value re-
quired to satisfy conditions). The control outputs this value to
the IGV/VFD SL. The SL compares DSPSR to actual duct
pressure and determines the required IGV position or VFD
speed. The required position/speed is sent to the IGV actuator
or VFD via Channel 16. The IGV responds to the position sig-
nal by opening or closing the supply fan inlet guide vanes; the
VFD responds to the speed signal by increasing or decreasing
supply fan motor speed.
If the fan status is not on within 1 minute of the fan start, the
fan relay commanded state is evaluated. If the state is on, the
ML control will check if the fan failure alarm has been tripped.
If the alarm has not tripped, algorithm will continue controlling
supply fan volume until the alarm is set (adding a 1 minute de-
lay). If the alarm has tripped, then the fan state is considered off
and the IGV actuator will be driven closed or VFD will be
turned off.
Algorithm — DSPSR = PID function on (demand term) where
(demand term) = Static Pressure Set Point – Static Pressure.
Configuration — To enable Duct Pressure mode, press
to enter into the Service function. Enter the pass-
word. Press to enter into the User Configuration sub-
function. Scroll down to DPEN. The current configuration will
be shown. The default is 0 (disabled). Press
the Duct Pressure mode. The acceptable range of values is 0
and 1, where 0 is disabled and 1 is enabled.
29
SET POINT RANGE
HHL 0 to 100%
DEFINITION
to enable
ENTER