23
®
Model MSX Make-Up Air
Check Operation - Recirculating
Units (optional)
NOTE
Blower Start-Up, steps 1-5 should be performed
before the blower is run.
Recirculation Operation
The recirculation operation option is recommended
when the ventilation equipment provides the primary
source of heating for the space. Recirculation can
vary from 100% return air to 100% outside air. Control
strategies include 2-position and modulating dampers.
Before the unit is left in service, the recirculation
control system should be tested.
Modulating
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 0, the return air damper will
open. When the potentiometer is
at 100, the return air damper will
close. The damper actuator may
take a few minutes to open or
close.
2-Position Damper
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 to close.
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.
With Maxitr ol 44 Room Thermostat
70
65
75
80
85
90
60
55
GREENHECK
®
(OPTIONAL)
BLOWER
DIRTY FIL TERS
MAIN V AL VES
RECIRCULA TION
EXHAUST
SUPPL Y
HEA T
(OPTIONAL)
2-Position
Damper Control
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
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
Building Pressure 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 pressure sensing device.
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.
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.
This picture shows a typical
photohelic setting. Typical
settings are 0.0 inch wc
for the lower and 0.10 inch
wc 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.
Pressure Setting Knobs
Pressure Setting
Needles
Pressure Indicating
Needle
Photohelic Gauge
