Greenheck IG / IGX (464104 IOM) (Pre-2009) - Manual (Page 43)

43
Start-Up - 4:1 Electronic Modulation
High Fire
Adjustment
Step 2 Check the High Fire Manifold
Pressure
Using a manometer, measure the high fire manifold
pressure at the pressure test port. Refer to the gas
train layout in the reference section for the test port
location.
The recommended high fire manifold pressure is 3 1 ⁄
2
inches wc for natural gas and 10 inches wc for LP
Gas.
If needed, adjust the high fire screw on the shut-off
valve to set the high fire manifold pressure.
Counterclockwise rotation will decrease the gas
pressure and clockwise rotation will increase the gas
pressure.
Step 1 Send the Unit to High Fire
To send the unit to high fire, press and hold the up,
down and enter keys. The unit will remain at high fire
until the escape key is pressed.
WARNING!
If the unit is forced to high fire, it will remain at high fire until the escape key is pressed.
NOTE!
Forcing the unit to high fire in mild weather conditions may cause the high limit switch to trip. If the
switch trips, it will reset once the discharge air temperature is at a safe level.
NOTE!
A second high limit with a manual reset is located in the control center.
NOTE!
After modifying a setting, the enter key must be pressed to save the change. If the enter key is not
pressed the display will return to the program menu without saving the change.
Step 3 Send Unit to Low Fire
Remove and isolate one wire from the modulating gas valve terminal to send the unit to low fire.
Start-Up
Escape
Down Enter
Up
4:1 Modulation Manifold
Pressure (in. wc)
Natural Gas LP
Low Fire 1 ⁄
3
1
High Fire 3 1 ⁄
2
10