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Power-up/Standby
After power is supplied to the unit:
1. The ignition control will reset and perform a self-
check routine.
2. The diagnostic LED will flash for up to four
seconds.
3. The ignition control will begin scanning the
thermostats.
Heat Mode
When the thermostat or discharge temperature
controls call for heat:
1. The ignition control will check that the pressure
switch for the combustion blower is open.
2. The combustion blower will be energized and the
15-second pre-purge begins.
3. The gas valve is energized and the igniter will spark
for up to 10 seconds.
Natural Gas - If a flame is not sensed during the
trial for ignition, two additional trials will be
attempted before going into lockout for one hour.
LP Gas - If a flame is not sensed during the trial for
ignition, the control will go into lockout for one
hour.
4. When a flame is sensed, sparking stops
immediately. The gas valve and combustion blower
remain energized.
5a. Two-stage control: The burner will light at 100%
fire and remain there for 10 seconds. The
thermostat will then operate the burners at high or
low fire, depending on the demand for heat.
5b. Electronic Modulation - The burner will light at
100% fire and remain there for 10 seconds. The
main burner gas valve will then modulate from
100% down to 50% as needed. If the burner
remains on low fire for an extended period of time,
the burner will shut off and re-light as necessary.
6. The ignition control constantly monitors the
thermostat, pressure switch, and burner flame to
assure proper operation.
7. When the thermostat or discharge temperature
controls are satisfied, the main valve is de-
energized and the combustion blower shuts off
following a 30-second post-purge period.
Recovery from Lockout
The ignition control will automatically reset after 1 hour
if the thermostat is still calling for heat. Prior to 1 hour,
a manual reset (cycle power to unit) is required. The
thermostat may be reset or the power interrupted for a
period of 5 seconds. See page 7 for
Ignition Control
Diagnostics
.
Sequence of Operation
1. Turn off power to the unit at the disconnect switch.
Close all manual gas valves.
2. Check that all gas and electrical connections are
weatherized.
3. Make sure that the combustion air inlet and the
combustion blower discharge are free from
obstructions.
4. Inspect the unit to make sure that no damage has
occurred during installation.
5. With the furnace control center access panel
removed, connect a “U” tube manometer to the
manifold pressure test port as shown in Figure 2.
This will be used for checking the manifold gas
pressure.
6. Set the thermostat or discharge temperature
controls to lowest setting.
7. Open all manual gas valves including the
combination gas valve and turn power on.
8. Call for heat with the thermostat or discharge
temperature controls and allow the burner to light.
Greenheck duct furnaces are equipped with an
automatic spark ignition system which
automatically lights the burner. DO NOT attempt to
light the burners manually.
9. After the burner is lit, check to make sure that the
supply blower is operating.
10.Verify that the gas controls sequence properly (see
Sequence of Operation below).
11.Check the manifold gas pressure (see
Burner
Adjustments
on pages 5 and 6).
Start-Up Procedure
4