1. Set the unit to high fire by placing a jumper between terminals 7 and 8 on the Maxitrol amplifier.
2. Measure the burner manifold pressure at each furnace at the pressure test port (see Figure 2) using a high
quality manometer that can measure low gas pressures. The pressure at high fire should be 3.5 in. wg for
natural gas and 10.0 in. wg for LP Gas. To change the pressure, adjust the high fire screw on the combination
gas valve.
3. To get the unit to low fire: Remove the wire from terminal 3 on the amplifier and isolate it from touching
anything. Set the discharge temperature selector to the highest setting. If there is a room override thermostat,
turn the dial to the highest setting.
4. Measure the manifold pressure on low fire, it should be 0.88 in. wg for natural gas and 2.5 in. wg for LP gas.
5. To adjust the low fire, remove the bypass cap (A) and turn screw (B) as shown in diagram. Adjust the screw
indicated in Figure 5 on the modulating valve.
6. Reconnect wire to terminal 3.
7. Remove jumper and place all wires back to where they were and plug the manifold pressure port.
Electronic Modulation Temperature Controls
For Energy Recovery Units without Temperature
Control Package
A Discharge Temperature Dial is used for temperature
control for electronic modulation. The temperature dial
will be located in the furnace control center.
For Energy Recovery Units with Temperature Control
Package
The Temperature Controller in the unit’s main control
center will provide the electronic modulation control.
High and Low Fire Settings for Electronic Modulation
Figure 5: Electronic Modulation Valves
Check the high and low gas pressures on initial start up per the instructions below. These settings are pre-set at
the factory, but should be adjusted in the field if necessary. Set the high fire first and the low fire second. The low
fire must always be checked if the high fire is changed.
Modulating Valve
Low fire adjustment
Combination Gas Valve
High fire adjustment
A
B
6
