Greenheck MSX (470658) - Manual (Page 24)

24 Modular Supply Make-Up Air Unit
®
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.
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.
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.
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
®
Potentiometer
Control
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