Model IGX Make-Up Air
25
®
Installation
Optional Components
Building Pressure Control
1. Mounting Pressure Sensor
Using the factory provided bracket, mount the pressure
sensor outside of the
building. The pressure
sensor mounting
location must be out
of prevailing winds and
away from supply or
exhaust fans to assure
accurate readings.
2. Running Pressure Tap Lines
Connect and run a pressure tube from the pressure
sensor outside of the building to the low pressure tap
on the back of the Photohelic
®
gauge. Run a second
pressure tube from the high pressure tap on the back
of the Photohelic
gauge to the space. If the Photohelic
gauge is located in the space to be controlled, the high
pressure tube is not required.
Note: Fifty feet of tubing is supplied with the unit.
If further tubing is required, this must be supplied
by others.
3. Setting the Desired Building Pressure
The Photohelic pressure gauge is used to set the
desired building pressure. The pressure is set by
adjusting the upper and lower pressure limits. A typical
positive pressure setting is: 0.0 in. wg (0.0 kPa) for the
lower and 0.10 in. wg (0.02 kPa) for the upper pressure
setting.
Building Static Pressure Sensor
(with microprocessor)
The controller will modulate the supply fan based upon
a comparison of the building static pressure set point
to the actual building static pressure level reported from
the sensor. Sensor shipped loose.
Duct Pressure Control
The optional microprocessor controller can be selected
to modulate the supply fan based upon a comparison
of the duct static pressure set point to the actual
duct static pressure level reported from the sensor.
The factory-supplied sensor will ship loose for field-
mounting and wiring. Further component identification
and terminal designation can be found by referencing
the unit specific ladder diagrams and supplemental
material supplied with the unit.
Carbon Dioxide (CO
2
) Sensor
This sensor is intended to measure the CO
2
concentration in the ventilated space or return air duct.
If the unit has been equipped with a microprocessor
controller, the CO
2
sensor will modulate either the VFD
or the return and outside air dampers based upon a
comparison of the CO
2
set point to the actual CO
2
levels reported from the sensor. The duct mount or room
mount sensor is shipped loose for field mounting and
wiring.
Duct-Mounted Smoke Detector
The duct smoke detector provides early detection of
smoke present in the HVAC duct system. The smoke
detector is designed to prevent the recirculation of
smoke by the air handling system. Complete system
shut down will occur in the event of smoke detection.
The detector will operate on 115 or 24 VAC. Output
terminals are provided for remote accessories such
as a horn, strobe, remote status indicators and reset
switches or push buttons.
Connections for Photohelic® Gauge
Factory Wiring
High Pressure Tap
to space
Low Pressure Tap
to outside
Pressure Indicating
Needle
Pressure Setting
Needles
Pressure Setting Knobs
