Startup
OAU-SVX006E-EN 55
High Fire and Low Fire Adjustment
To adjust high fire or low fi
re setting, please refer to
EXA STAR Modulating Valve document. This
document will ship with all gas heat units.
Failure to Ignite
• On the ini
tial startup, or after unit has been off long
periods of time, the first ignition trial may be
unsuccessful due to need to purge air from
manifold at startup.
• I
f ignition does not occur on the
first trial, the gas
and spark are shut-off by the ignition control and
the control enters an inter-purge period of
15 seconds, during which the d
raft inducer
continues to run.
• A
t the end of the inter-purge pe
riod, another trial for
ignition will be initiated.
• Control will initiate up to three ignition
trials on a
call for heat before lockout of control occurs.
• Control can be brought out of lockout by cycling call
for h
eat at the Main Unit Display.
Prior to completing the startup, check the appearance
o
f
the main burner flame. Refer to Figure 41, p. 55 for
flame characteristics of properly adjusted natural gas
systems.
Main burner flame
• The burner flame should be predominately blue in
co
lor and well defined and centered at the tube
entry as shown in Figure 41 above. Distorted flame
or yellow tip
ping of natural gas flame, or a long
yellow flame on propane, may be caused by lint and
dirt accumulation inside burner or at burner ports,
at air inlet between burner and manifold pipe, or
debris in the main burner orifice. Soft brush or
vacuum clean affected areas.
• P
oorly defined, substantially yellow flames, or
flames that appear lazy, indicate poor air supply to
burners or excessive burner input. Verify gas
supply type and manifold pressure with rating
plate.
• Po
or air supply can be caused by obstructions or
bl
ockage in heat exchanger tubes or vent discharge
pipe. Inspect and clean as necessary to eliminate
blockage. Vacuum any dirt or loose debris. Clean
heat exchanger tubes with stiff brush. Poor flame
characteristics can also be caused by flue gas
recirculation into combustion air supply. If
Pressure Settings
Fuel Type NG LP
Unit Inlet (in.) 7-14 10-14
Modulating Valve Inlet (in.) 5.0 10.0
Manifold (in.) 3.5 8.0
Low Fire (in.) 0.4 0.8
High Fire (in.) 3.5 8.0
Figure 41. Flame characteristics of properly-adjusted
natural gas systems
Burner Flame @ Start-up 1.2” w.c. Manifold
Pressure Draft Inducer – High Speed
Burner flame at startup: 1.2 in. WC manifold
pressure draft inducer—high speed
lue in color and well defined and centered at the tube entry a
Burner Flame @ High Fire 3.5” w.c. Manifold
Pressure Draft Inducer – High Speed
Burner flame at high fire: 3.5 in. WC manifold
pressure draft inducer—high speed
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