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®
Model MSX Make-Up Air
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 inch
wc for the lower pressure
setting and 0.10 inch wc 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.
With Maxitrol 44 Room Thermostat
70
65
75
80
85
90
60
55
(OPTIONAL)
BLOWER
DIRTY FILTERS
MAIN VALVES
EXHAUST
SUPPLY
HEAT
(OPTIONAL)
GREENHECK
®
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
A variable frequency drive (VFD) is used to control
air volumes. The VFD 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 and
modulating blowers. Before the unit is left in service,
the variable volume control system should be tested.
70
65
75
80
85
90
60
55
(OPTIONAL)
BLOWER
DIRTY FILTERS
MAIN VALVES
EXHAUST
SUPPLY
HEAT
(OPTIONAL)
GREENHECK
®
With Maxitrol 44 Room Thermostat
Potentiometer
Control
Check Operation - VAV Units
(optional)