Navien E110 (abnormal air pressure): what to check

Navien display

E110

“Abnormal air pressure”

NPE-A2, NPE-S2, NPN · NPE-2 User's Information Manual, p. 17; NPN User's Information Manual, p. 22
Owner checks, then technician

What it means

E110 is Navien’s abnormal air pressure code. On NPE-2 models the remedies cover the air intake filter and the exhaust pipe; on NPN models only the vent pipe. On NPE-A2 and NPE-S2 models the user’s manual names one cause directly: when dust or lint clogs the air intake filter, the heater stops working and shows “Error Code 110” NPE-2 User’s Information Manual, p. 14. Both tables also tell you to make sure the exhaust or vent pipe is free of obstructions NPE-2 User’s Information Manual, p. 17; NPN User’s Information Manual, p. 22.

Check these first

Go outside and look at the exhaust and intake terminations. Clear away snow, ice or anything else blocking them; Navien makes the building owner responsible for keeping them clear NPE-2 Installation & Operation Manual, p. 42. If a termination is on the roof or out of safe reach, leave it to a technician.
Look over the vent and intake pipes you can see indoors without taking anything apart. If any pipe or elbow is damaged, separated at a joint, or shows corrosion, rust or melting, turn the heater off and stop using it NPE-2 User’s Information Manual, p. 5; NPN User’s Information Manual, p. 5.
On NPE-A2 and NPE-S2 models, clean the air intake filter NPE-2 User’s Information Manual, p. 14. Turn the heater off with the Power button and disconnect its power supply before you remove the front cover p. 6. The filter is at the top left, held by one screw. Wash it with a toothbrush under clean running water, let it dry completely, then refit the filter and the cover before you reconnect power p. 14.
Reset the heater once. On NPE-A2 and NPE-S2 models, press Back NPE-2 User’s Information Manual, p. 10. On NPN models, press Reset on the front panel, or OK on the remote for outdoor models NPN User’s Information Manual, pp. 12, 21.

Navien recommends cleaning the NPE-2 air intake filter every 3–4 months, and inspecting the vent termination and air intake once a year NPE-2 User’s Information Manual, pp. 5, 14.

When to call a licensed technician

E110 returns after the terminations are clear and, on NPE-2 models, the filter is clean NPE-2 User’s Information Manual, p. 16; NPN User’s Information Manual, p. 21.
A vent or intake pipe is damaged, loose or separated. On NPE-2 models only licensed professionals should install venting NPE-2 Installation & Operation Manual, p. 42; on NPN models venting is for a qualified service agency NPN Installation and Operation Manual, p. 16.
A technician can check the installed vent run against Navien’s limits. On NPE-2 models a 2 in. vent can run up to 75 ft (23 m), reduced by 8 ft (2.4 m) for each 90° elbow, with no more than six elbows; a 3 in. vent can run up to 150 ft (45 m), reduced by 5 ft (1.5 m) per elbow, with no more than eight NPE-2 Installation & Operation Manual, p. 54. On NPN models the concentric vent can run 43 ft (13 m) with no elbows, 5 ft less for each 90° elbow, and four elbows at most NPN Installation and Operation Manual, p. 42.

Notes for different models

The NPE-2 table and the NR-21DU remote manual give two remedies for E110, a clear exhaust pipe and a clean intake air filter NPE-2 User’s Information Manual, p. 17; NR-21DU Remote Controller Manual, p. 31. The NPN table gives only the vent pipe check p. 22, and the NPN manuals describe no air intake filter.

The vent systems differ. NPE-2 heaters are Category IV appliances whose vent runs under positive pressure NPE-2 Installation & Operation Manual, p. 42. NPN heaters are Category III appliances on a concentric vent, one pipe with separate ducts for combustion air and exhaust NPN Installation and Operation Manual, p. 35.

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