Lennox Furnace: Poor ignition or combustion resonance – Lennox EL195UHNE

Poor ignition or combustion resonance - Lennox EL195UHNE on a Lennox furnace: Burner is slow/hard to light or runs with a loud resonance (rumble/howl). On the EL195UHNE this is usually the air orifice in the air intake coupling, gas manifold pressure, or the signal pressure that drives the gas valve.

Homeowner with a furnace problem? Call (647) 657-2977 or book a service call — licensed technicians across Vaughan and the GTA.

Applies to: EL195UHNE (EL195UH040/060/080/100NE)

Common causes of poor ignition or combustion resonance - lennox el195uhne

• Wrong or loose air orifice (oversized = hard ignition, undersized = resonance)
• Blocked air inlet screen
• Manifold pressure out of range
• Signal pressure out of range from vent/intake restriction, plugged drain, or kinked signal hoses
• Faulty gas valve

How to fix poor ignition or combustion resonance - lennox el195uhne: step by step

1. Check the air orifice: correct part number for the size (Table 20), fully seated against the elbow, and the air inlet screen clear.
2. Production orifices: 040 = 0.800 (16), 060 = 0.995 (14), 080 = 1.105 (12), 100 = 1.250 (06).
3. Measure manifold pressure after 8 minutes of run time: natural gas 3.2-3.8 in. w.c. at 0-4500 ft. The valve is not adjustable - do not try to adjust it.
4. If manifold pressure is in range but the problem remains, change the air orifice: for resonance use the larger (more air) orifice, for hard ignition the smaller (less air) orifice - see Table 20 catalog numbers.
5. If manifold pressure is out of range, measure signal pressure (Table 19, e.g. 0.80-0.93 in. w.c. for 040 at 0-4500 ft). If signal is in range, replace the gas valve.
6. If signal pressure is out of range, check vent/intake for restriction, plugged condensate drain, plugged inlet screen, and signal hoses for kinks or loose fit; fix and recheck manifold pressure - if still wrong, replace the gas valve.
7. To reach the orifice: power and gas off, remove the black air pressure tube, loosen the gray coupling clamps (5/16 in. nut driver), remove the air intake coupling; reassemble fully seated and recheck pressures.

If the unit shows an error code, look it up: Lennox Furnace codes

Models

Lennox EL195UHNE

EL195UH040NE36BEL195UH060NE36BEL195UH080NE48CEL195UH100NE60C

EL296UHV

EL296UH045XV36BEL296UH070XV36BEL296UH090XV36CEL296UH090XV48CEL296UH090XV60CEL296UH110XV48CEL296UH110XV60CEL296UH135XV60D

Lennox ML180UHE

ML180UH045E36AKML180UH045XE36AKML180UH070E36AKML180UH070E36BKML180UH070XE36AKML180UH070XE36BKML180UH090E48BKML180UH090E60CKML180UH090XE48BKML180UH110E60CKML180UH110XE60CKML180UH135E60DK

Lennox SL280UHV

SL280UH060NV36ASL280UH070V36ASL280UH080NV48BSL280UH080NV60CSL280UH090V36BSL280UH090V48BSL280UH090V60CSL280UH100NV60CSL280UH110V60CSL280UH135V60D

Lennox SL297NV

SL297UH040NV36BSL297UH060NV36BSL297UH080NV48CSL297UH080NV60C