Direct Gas Make-Up Air
36
Set both knobs at the lowest setting and the damper
should open. It may take one to two minutes for the
damper to reach the desired position.
Reset the correct pressure limits before starting the unit.
Typical settings are 0.0 in. wg (0 kPa) for the lower and
0.10 in. wg (0.02 kPa) for the upper pressure setting.
The needle in this photo indicates a negative building
pressure. During correct operation, the indicating needle
will remain between or near the setting needles.
External Signal
A modulating spring return actuator is used to control
the return air amounts. Return air damper modulates
from fully open to fully closed based on an external
2-10 VDC or 4-20 mA signal (by others).
The return air damper will close with a 10 VDC or 20 mA
signal. The return air damper should open with a 2 VDC
or 4mA signal. The damper actuator may take a few
minutes to open or close.
The recirculation operation option is recommended
when the ventilation equipment provides the primary
source of heating for the space or when exhaust fan
tracking is required. A minimum of 20% outdoor air is
mixed with up to 80% recirculated air. Control strategies
include 2-position option and modulating options.
During commissioning, test the recirculation control
system.
2-Position Option
A 2-position spring return actuator is used to control
the return air amounts. The damper
moves from open to closed. If
power is cut to the unit, the outdoor
air damper will fail closed.
Turn the recirculating switch on
the remote control panel to each
position and confirm that the return
air damper adjusts accordingly. The
damper actuator may take a few
minutes to open or close.
Modulating Options
Potentiometer Control
A modulating spring return actuator is used to control
the return air amounts. The return air damper modulates
from fully open to fully closed
based on a signal from a remote
potentiometer.
To test potentiometer operation, turn
the potentiometer to the two extremes.
Confirm that the return air damper
fully opens and fully closes. When
the potentiometer is at minmum, the
return air damper will open. When
the potentiometer is at maximum,
the return air damper will close. The
damper actuator may take a few
minutes to open or close.
Building Pressure Control
A floating point spring return actuator
is used to control the return air
amounts. The return air damper
modulates from fully open to fully
closed based on a signal from a
remote pressure sensing device.
On the Photohelic
®
gauge, turn both
knobs to the upper most pressure
setting. You may have to remove the
outdoor pressure tap tubing. The
return air damper should close.
70
65
75
80
85
90
60
55
(OPTIONAL)
BLOWER
DIRTY FIL TERS
MAIN V AL VES
RECIRCULA TION
EXHAUST
SUPPL Y
HEA T
(OPTIONAL)
2-Position
Damper Control
EXHAUST
(OPTIONAL)
(OPTIONAL)
55
60
65
70
75
80
85
90
SUPPLY
HEAT
DIRTY FILTERS
MAIN VALVES
BLOWERS
Potentiometer
Control
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
Start-Up: Direct Gas-Fired Heating
Optional Features
Recirculation Operation
Photohelic
®
Gauge
Pressure Indicating
Needle
Pressure Setting
Needles
Pressure Setting Knobs
