Lennox E223: low pressure switch failed open

Furnace control display or LED

E223

“Low pressure switch failed open.”

Printed on 13 model series · 13 documents

SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, ML296*V, ML297*V, G71MPP · 508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 508577-02 p. 44; 1901-L1 p. 14; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 66

Technician

What it means

E223 means the control expected the low pressure switch to close on a call for heat and it stayed open. The compact ML180UHVK table words it as “LOW PRESSURE SW FAILED TO CLOSE (STUCK OPEN)” 508547-01, p. 26. The action in the SL297UHNVK table: check the pressure (inches w.c.) at which the low pressure switch closes on a heat call, measure the operating pressure (inches w.c.), and inspect the vent and the combustion air inducer for correct operation and restriction; the furnace resumes normal operation after the fault clears 508585-02, p. 50.

The SL297UHNVK table also has codes for a high pressure switch: E225, “High pressure switch failed open.”, and E226 508585-02, p. 50. On the K editions of the EL180, EL195, EL196, ML180, ML193 and ML196, whose tables have no high pressure switch codes, E223 reads “Pressure switch failed open.” with the same checks for “pressure switch” 508569-01, p. 46; 508575-02, p. 47.

Lennox’s thermostat alert 223 is “GF Low Pressure Switch Open”, priority Service Soon. Besides the pressure checks, it lists blockages in the vent, the combustion air inducer, a blocked cold end heater box, condensate drain or drain strainers, cracked hoses, and the levelness of the unit, and it clears automatically after the issue is corrected 100017, p. 20. Lennox’s documents do not say that alert 223 and display code E223 report the same event.

Check these first

Lennox’s owner’s manuals have no code table and give no steps for E223. What they give is a general list for a unit that will not operate, to work through before calling a Lennox service technician. In the SLP99DFVK manual the order is:

Check that the electrical disconnect switches are ON 508590-01, p. 5.
Check the room thermostat for proper setting 508590-01, p. 5.
Replace any blown fuses or reset circuit breakers 508590-01, p. 5.
Check that the gas valve is ON 508590-01, p. 5. Its switch is behind the outer access panel; the manual’s gas valve steps set the thermostat to the lowest setting and turn off all electrical power to the unit before that panel comes off, and the switch is moved by hand only, never with tools 508590-01, p. 4.
Check that the air filter is not plugged, which would limit air flow 508590-01, p. 5. The SLP99DFVK manual says its filters are installed external to the unit, should be inspected monthly, and that a filter must be in place when the unit is operating 508590-01, p. 4. Before any service or maintenance, it says to turn the electrical power to the unit OFF at the disconnect switch 508590-01, p. 2.
Check that gas is turned on at the meter 508590-01, p. 5.
Check that the manual main shut-off valve is open 508590-01, p. 5.

Then record the model and serial number from the nameplate and call 508590-01, p. 5. The list is not tied to any code. More on it, and on how other Lennox manuals word it: owner checks before a service call.

The SLP99DFVK manual lists inspecting the venting system and the condensate drain and trap among the maintenance procedures that should only be conducted by a licensed professional service technician 508590-01, p. 5. Inspecting the rubber hoses connected to the pressure switches is part of the annual maintenance it gives to a licensed professional service technician 508590-01, p. 6.

When to call a licensed technician

Checking the pressure at which the switch closes and measuring the operating pressure, in inches of water column 508585-02, p. 50.
Inspecting the vent and the combustion air inducer for correct operation and restriction 508585-02, p. 50.
The alert guide’s further checks for alert 223: a blocked cold end heater box, condensate drain or drain strainers, cracked hoses, and the levelness of the unit 100017, p. 20.
The display shows E271, a soft lockout whose last retry failed due to the pressure switch opening 508585-02, p. 51.
The furnace still will not run after the checklist 508590-01, p. 5.
E223 keeps coming back after it clears. The owner’s manuals give no step for that; these pages send it to the technician.

Notes for different models

Series or document	Code	Wording	Source
SL280V, SL280NV, SL297NV, EL280E, EL296V, EL296E, EL297V, EL297E, ML296V, ML297V	E223	“Low pressure switch failed open.”	508585-02, p. 50; 1246-L10, p. 13; 508521-01, p. 43; 508907-01, p. 47
SLP98V, SLP99V, G71MPP	E223	“Low pressure switch failed open - Refer to troubleshooting in installation instruction.” The action gives the pressures in inches of water column.	508589-02, p. 46; 506610-01, p. 63; 506509-01, p. 66
K editions of the EL180, EL195, EL196, ML180, ML193, ML196	E223	“Pressure switch failed open.”	508575-02, p. 47; 508569-01, p. 46; 508547-01, p. 49
ML180UHVK, compact table	E223	“LOW PRESSURE SW FAILED TO CLOSE (STUCK OPEN)”	508547-01, p. 26
Lennox thermostat alert table	223	“GF Low Pressure Switch Open”, Service Soon	100017, p. 20

The ML180UHVK instructions use both forms: “Pressure switch failed open.” in the detailed table 508547-01, p. 49 and “LOW PRESSURE SW FAILED TO CLOSE” in the compact one 508547-01, p. 26.

Furnaces with a red LED show a pressure switch that does not close as a flash count; the documents do not translate flash counts into E-codes. On the 13-flash board 103217-03, 9 flashes is “Pressure Switch failed to close or opened during heat demand” 507966-04, p. 40. In the 9-flash tables of the ML193UH, ML195UH and ML180DF, 3 flashes is “Pressure switch open with combustion air inducer energized.” 507121-01, p. 39; 507268-03, p. 39; 507326-01, p. 21.