Greenheck IGX Installation, Operation And Maintenance Manual page 26

Furnace Controls
Staged Temperature Controls
The furnace stage controls are located in the furnace control center. The discharge temperature setting is
located on the control furthest to the left (See Figure 8). One control is provided for each stage of heating.
The offset and differential settings for each stage are preset at the factory; however, field adjustment may be
required to get the best control for your application. See literature provided for information on setting these
controls.
The following are the descriptions of the furnace controls available.
2 Stage (100 - 400 MBH)
2 Stage (500 - 800 MBH)
3 Stage (1050 - 1200 MBH)
4 Stage (500 - 800 MBH)
6 Stage (1050 - 1200 MBH)
High and Low Fire Settings for Staged Burner Controls
Setting Manifold Pressure for Two Stage Gas Control
1. Set the unit to high fire by setting the discharge
temperature control or thermostat to its maximum
setting. If the ambient temperature is warm, the unit
may not stay at high fire.
2. Measure the burner manifold pressure at the
manifold pressure test port (see Figure 7) using a
"U" tube manometer. The pressure on high fire
should be 3.5 inches wc for natural gas and 10
inches wc for LP gas. To change the pressure,
adjust the regulator adjustment screw on the
combination gas valve. Clockwise rotation will
Figure 9: Combination Gas Valve
2 stage furnace (50%, 100%)
1st furnace 1 stage (50%)
2nd furnace 1 stage (100%)
1st furnace 1 stage (33%)
2nd furnace 1 stage (67%)
3rd furnace 1 stage (100%)
1st furnace 2 stage (25%, 50%)
2nd furnace 2 stage (75%, 100%)
1st furnace 2 stage (17%, 33%)
2nd furnace 2 stage (50%, 67%)
3rd furnace 2 stage (83%, 100%)
Solenoid
decrease the gas pressure and counter clockwise
rotation will increase the gas pressure.
3. Set the unit to low fire by removing the wire from
the high fire terminal on the combination gas valve
(See Figure 9). Clockwise rotation will decrease the
gas pressure and counter clockwise rotation will
increase the gas pressure.
4. The manifold pressure on low fire for natural gas
should be .88 inches wc and for LP gas, 2.5 inches
wc. To change the pressure, use the low fire
adjustment screw on the combination gas valve.
High Fire Adjustment
Low Fire Adjustment
26
Figure 8: Staged Control
High Fire Terminal