Poor ignition or combustion resonance - Lennox EL195UHNE

What is going on

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.

Likely causes

• 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

Check in this order

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.

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