Greenheck IG / IGX (464104 IOM) (Pre-2009) - Manual (Page 42)

42
Start-Up
Start-Up - 2:1 Electronic Modulation
NOTE!
The low fire manifold pressure should always be
rechecked after adjusting the high fire.
Step 1 Send Unit to High Fire
Turn the temperature selector to its maximum setting to send the unit to high fire.
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.
Step 2 Check the High Fire Manifold Pressure
With the unit at high fire, use a manometer to measure the burner manifold pressure at the manifold pressure
test port. See the gas train layout in the reference section for the manifold pressure 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, use the high fire adjustment screw on the shut-off gas valve to adjust the high fire manifold pressure.
Counterclockwise rotation will decrease the gas pressure and clockwise rotation will increase the gas pressure.
Step 4 Check the Low Fire Manifold Pressures
With the unit at low fire, use a manometer to measure the burner manifold pressure at the manifold pressure test
port. See the gas train layout in the reference section for the manifold pressure test port location.
The recommended low fire manifold pressure is 7 ⁄
8
inch wc for natural gas and 2 1 ⁄
2
inches wc for LP Gas.
If needed use the low fire adjustment screw on the modulating gas valve to adjust the low fire manifold pressure.
Counterclockwise rotation will decrease the gas pressure and clockwise rotation will increase the gas pressure.
Once the low fire is set, reattach the disconnected wire to the modulating valve and reset the temperature
selector.
2:1 Manifold
Pressure (inches wc)
Natural Gas LP
Low Fire 7 ⁄
8
2 1 ⁄
2
High Fire 3 1 ⁄
2
10
Low Fire
Adjustment
Terminal
High Fire
Adjustment
IMPORTANT!
Once the high and low fire manifold pressures
are properly set, reset the discharge air
temperature to the desired setting.