Indirect Gas-Fired Heat Modules
19
The modulating gas valve and the single stage valve are
both controlled by an A1092 Control System.
1. Connect a manometer to the test port on the burner
manifold.
2. Set the furnace to High Fire by turning the
temperature on the remote temperature selector dial
to maximum setting. This will cause both gas valves
to go into their high fire positions.
3. Set the high fire manifold gas pressure by turning
the adjusting screw on the single stage valve. The
correct pressure is 3.5 in. wg for
natural gas or 10.0 in. wg for LP
gas. Verify the unit is in high fire
by measuring VDC at modulating
valve. If greater than 15 VDC, then
the unit is in high fire.
4. Set the unit to low fire by
disconnecting one of the wires
connected to the top of the modulating valve.
5. Set the low fire on the modulating gas valve by
adjusting the needle valve on the side of the gas
valve. Low fire gas pressure should be 0.875 in. wg
for natural gas or 2.5 in. wg for LP gas.
6. Return the A1092 Controller to normal operation by
reconnecting the wire on the modulating valve and
turning down the temperature selector.
7. Shut down the furnace and then remove the
manometer from the manifold and reinstall the plug
in the test port.
8. Return the furnace to normal operation.
Furnaces with electronically modulated 2:1 turndown
use a single stage valve for primary gas control. It
controls the high fire gas supply.
In addition to the single stage gas valve, there is a
modulating gas valve located just after the combination
valve.
Both of these valves require adjustment at the
time of unit start-up
.
High Fire
Adjusting Screw
With 2:1 Turndown Electronic
Modulation
Typical Modulating
Gas Valve
Typical Single Stage
Gas Valve
Modulating
Valve
Single Stage
Valve
Single Section
Burner Manifold
Remote Temperature
Sensor
Remote
Temperature Dial
Amplifier
MAXITROL
SELECTRA
MAXITROL
SELECTRA
A1092
50
70
80
90
60
MAXITROL
SELECTRA
Ignition
Controller
®
