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Building Pressure Control —
a variable frequency drive is
controlled according to input from a
pressure sensing device.
Turn both knobs to the upper most
pressure setting. You may have to
remove the outdoor pressure tap
tubing. VAV systems should go to
maximum speed. Set both knobs
at the lowest setting and the VAV
systems should go to minimum
speed.
Reset the correct pressure limits
before starting the unit.
This picture depicts a typical
photohelic setting. Typical
settings are 0.0 in. wg for
the lower pressure setting
and 0.10 in. wg for the upper
pressure setting. The needle
indicates a negative building
pressure. During correct
operation, the indicating
needle will remain between
or near the setting needles.
External Signal — a variable
frequency drive is controlled according to input from
an external 2-10 VDC or 4-20 mA signal (by others).
A 2 VDC or 4 mA signal will send the blower to low
speed. The blower will go to maximum speed with a
10 VDC or 20 mA signal.
Variable Kitchen Control — A variable frequency
drive is controlled by input from a remote speed
control. This unit allows automatic adjustment of
make-up air volumes based on varying cooking loads.
70
65
75
80
85
90
60
55
(OPTIONAL)
BLOWER
DIRTY FIL TERS
MAIN V AL VES
EXHAUST
SUPPL Y
HEA T
(OPTIONAL)
PHOTOHELIC
Building
Pressure Control
Pressure Setting Knobs
Pressure Setting
Needles
Pressure Indicating
Needle
Photohelic Gauge
NOTE
Blower Start-Up, Steps 1-5 should be performed
before the blower is run.
NOTE
For maintenance issues associated with variable
frequency drives, consult the drive’s manual
supplied with the unit. The drives are programmed
at the factory and should not need any adjustment
during installation and start-up. For kitchen
applications, the drive may be located in the kitchen
or in the unit.
Modulating
Potentiometer Control — a variable frequency drive
is controlled by input from a remote
speed selector (potentiometer). This
unit allows easy manual adjustment
of make-up air volumes. To test
potentiometer operation, turn the
potentiometer to the two extremes.
With variable volume, make sure the
fan goes to maximum and minimum
speed.
When the potentiometer is at 0, the
fan speed will be at its minimum.
When the potentiometer is at 100,
the fan will be at its maximum speed.
2-Speed VFD Motor
A variable frequency drive (VFD) is used on a single
speed motor to control air volumes. The VFD is
factory-programmed for 2 speed operations. It can be
switched to low or high speed from a remote control
panel. Turn the fan speed switch on the remote control
panel to each position and confirm that the fan speed
adjusts accordingly.
Variable Volume Operation
The variable volume option is recommended when
a building’s exhaust volume may vary. This option
enables the make-up air volume to track with the
exhaust volume, providing only the amount of make-
up air required. Control strategies include 2-speed
VFD motors and modulating blowers. Before the unit
is left in service, the variable volume control system
should be tested.
EXHAUST
(OPTIONAL)
(OPTIONAL)
55
60
65
70
75
80
85
90
SUPPLY
HEAT
DIRTY FILTERS
MAIN VALVES
BLOWERS
Potentiometer
Control
Check Operation - VAV Units
(optional)
®
Model IG / IGX Make-Up Air