10 components coveredField manual · Furnace
Lennox ML196 / EL296 / ML193 / ML195 96% condensing gas furnaces: quick sheet
Covers: Lennox condensing (90%+ AFUE) gas furnaces. Single-stage Merit: ML196UH, ML196DF, ML196UHE, ML196E, ML196EK, and the older ML193UH, ML195UH, ML195DF. Two-stage Elite: EL296UH, EL296DF, EL296UHE, EL296UHV, EL296V, EL296E (and the similar SLP98 variable-capacity units, which share the display codes). Model string example ML196UH070XE36B: 070 = input (about 66,000 Btuh), X = California low-NOx, E = constant-torque blower (V = variable speed, P = PSC on older units), 36 = add-on cooling range, B = cabinet width. K suffix = refrigerant detection control for A2L systems.
These are Lennox's 96% AFUE condensing furnaces with hot surface ignition, PVC venting and a condensate trap. Single-stage units (ML193, ML195 and most ML196) use a single red LED that flashes a count; two-stage EL296 and SLP98 units use a SureLight control with a display that shows three-digit codes such as E223 or E250. Pressure switch faults are the most common call on these units and are often caused by water in the trap, hose or vent rather than a bad switch.
Safety first
- Gas valve, manifold pressure, burners, heat exchanger and PVC venting work are blocked: refer to a licensed gas technician.
- Never jumper or bypass a pressure switch, limit or rollout switch.
- A rollout trip or E241 can mean flue gas or gas valve problems: shut down, check for CO and refer.
- Read the code before removing power, then lock out 120 V before touching wiring.
- K models with refrigerant detection: do not disable the sensor.
How it works
Sequence matches the 80% furnaces: pressure switch proves inducer airflow, pre-purge, igniter warm-up, gas valve opens, flame sensor proves flame, blower starts after the heat-on delay. A secondary heat exchanger condenses water from the flue gas, which drains through the trap and drain line.
Two-stage EL296 units use separate low-fire and high-fire pressure switches and a two-stage gas valve. They can light on high fire and then drop to low fire; code E229 (ignition on high fire) is logged when the low-fire switch did not close. E228 is logged when the control cannot calibrate the pressure switch at start-up.
A blocked condensate trap, sagging drain line or water in the pressure switch hose pushes the switch open. That gives E223/E227 on display units or 3 or 6 flashes on single-LED units, even when the switch itself is good.
Repeated failures put the control into a timed soft lockout (Watchguard, about one hour) that clears when the timer runs out or when a heat call finishes normally. On EL296 units E270 means the control ran out of ignition retries without sensing flame, and E250 means the limit circuit is open; if the limit does not close within about 3 minutes the unit goes into a one-hour soft lockout (timing from one source).
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Always confirm values against the tech sheet for the exact model.
OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Condensing gas furnace with PVC vent pipes and metal ductwork in a utility room by Wtshymanski, CC BY-SA 4.0
