Lennox SL280UHNV Series Unit Information page 35

Troubleshooting Poor Ignition or Combustion Resonance Issues
Has the unit inducer RPM been reduced
to 4300 RPM? Does not apply to -040
unit
Check Air Orifice
See Figure 19
Check the following
1-Does the unit have the correct
air orifice size?
2 -Is the orifice fully seated tight
against the elbow ?
3 -Is the orifice damaged in any­
way?
4 - Is the air inlet screen clear of
any obstruction ?
Correct any problems found.
Is ignition or resonance issue
resolved ?
Check Gas Manifold Pressure
Gas manifold pressure within
range?
Check signal Pressure
Signal pressure
within range ?
Check the following
1-. Vent /air intake pipe restriction.
2- Plugged air inlet screen
3 - Signal hoses to gas valve
for kinks, loose fit or plugging.
Correct any problems found.
Manifold pressure correct ?
Is ignition or resonance
issue resolved?
Replace air orifice.
No
Yes
Yes
No
Yes
No
Yes
No
No
Yes
Yes
No
FIGURE 21
Page 35
Contact your Service
Representative for assistance
Troubleshooting is complete
Replace air orifice.
Replace gas valve
Replace gas valve
Troubleshooting is complete