Operation - Recirculating Units (optional)
NOTE
Blower
Recirculation Operation
The recirculation operation option is recommended when the ventilation equipment provides the primary source of heating for the space. A minimum of 20% outdoor air is mixed with up to 80% filtered recirculated
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.
BLOWER
EXHAUST (OPTIONAL)
SUPPLY
|
| MAIN VALVES |
HEAT |
| |
|
| DIRTY FILTERS |
75 | 70 |
|
80 | 65 | (OPTIONAL) |
85 | 60 | |
90 | 55 |
|
PHOTOHELIC
GREENHECK
With Maxitrol 44 Room Thermostat
Building
Pressure Control
air. Control strategies include
Before the unit is left in service, the recirculation control system should be tested.
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.
2-Position Damper
A
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 |
|
| DIRTY FILTERS |
|
|
| |
the remote control panel to each | 75 | 70 | (OPTIONAL) |
80 | 65 | ||
85 | 60 |
| |
55 |
| ||
| 90 |
|
This picture shows a typical photohelic setting. Typical settings are 0.0 in. wg for the lower and 0.10 in. wg 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.
Pressure Indicating | Pressure Setting |
Needle | Needles |
Pressure Setting Knobs
Photohelic Gauge
position and confirm that the return | ® GREENHECK |
| |
air damper adjusts accordingly. | |
The damper actuator may take a | Damper Control |
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 858090 655560 extremes. With 80/20 recirculation,
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.
20Model VSU
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
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.
Operation - Electrical
Electrical Sequence
1.Exhaust Fan Contact (S1) Closed (optional)
•Power passes to N.C. exhaust overload contact
(ST2 OL) (optional)
•Power passes to exhaust starter(s) ST2
•N.O. exhaust starter switches are energized and closed
•Power passes to exhaust fans
•Exhaust fan(s) (M2) start
2.Supply Fan Contact (S2) Closed
•Power passes through N.C. field supplied fire contact (FSC)
•Power passes through N.O. exhaust fan contact
(ST2), which is closed when the exhaust relay (ST2) is activated (optional)
®