Navien Error Code 10 (E010 / 10E): Abnormal Air Pressure on Older Navien Units (Meaning, Causes, Fixes)
What the code means
Navien's NR/NP series service manual (version 2.0, 2010) and the CH-180 service manual both list E010 as Abnormal air pressure. The NR/NP manual explains how the control decides this. During pre-purge, if the fan is turning but the air volume (air pressure) sensor voltage never reaches the level needed for ignition, the unit retries pre-purge; after 10 failed pre-purges in a row it declares an air pressure error (or an air pressure hose error) and locks out. During combustion, if the fan is running 1,000 RPM or more above its standard speed, the control treats that as an air pressure error, stops burning and keeps the fan running, then cancels the error once the fan speed comes back to within 500 RPM of standard. In plain terms, something is restricting air in or out of the unit, the small hose to the air pressure sensor is damaged or holding water, or the sensor or board has failed. If you have a current NPE or NCB-E model, its manuals call this E110; see our Navien E110 page.
Likely causes
- A blocked vent or fresh-air (intake) pipe, for example snow, leaves, a nest or debris at the outside termination. This is the first check on Navien's E010 list.
- A dirty air filter. Navien's error list says to check and clean it.
- A torn, holed or water-filled air pressure hose. The NR/NP service manual says to inspect it for tears and holes and for water left in the hose after installation.
- A clogged condensate hose or drain, which can back water up into the vent
- Rainwater collected in the air supply or exhaust pipe because of a dent or a pipe installed sloping the wrong way
- Exhaust gas getting pulled back into the air supply. The service manual notes this inflow of exhaust gas makes noise.
- A clogged venturi (burner) hole
- A defective air pressure sensor or control board (PCB)
Safe DIY checks
Turn off power at the furnace/HVAC service switch and the breaker before opening panels. Shut the gas valve before any work near the burners, and never disconnect or alter the gas line. If you smell gas, leave the house and call your gas utility.
- Turn the unit off and disconnect power before you open the cover.
- Go outside and look at both vent terminations, the exhaust and the fresh-air intake. Clear away snow, ice, leaves, nests or anything blocking them.
- Look along any vent pipe you can see for dents, sags or spots where rainwater could sit, and note them for your installer.
- Check and clean the air filter, as Navien's error list says. On these older units the filter is behind the front cover.
- Check that the condensate drain hose isn't kinked, frozen or clogged and that it drains freely.
- Restore power and try hot water or heat again. If error 10 comes back after the vents, filter and drain are clear, stop resetting it and call for service.
🛠 When to call a pro
- Error 10 keeps coming back after the vents, air filter and condensate drain have been checked
- Inspecting and replacing the air pressure sensor hose, and clearing water out of it
- Checking the venturi (burner) hole, the air pressure sensor and the PCB. The NR/NP service manual checks the sensor's signal voltage and the fan's operating voltage as part of its 10E flowchart.
- Fixing vent slope, dents, length or termination problems, or exhaust recirculating into the intake. Venting on a gas appliance should be corrected by a licensed installer.
- The manual notes that if the error happens only now and then on some older units, Navien's fix was a replacement controller. That is a technician call.
Parts that commonly fix it
Always match the part number to your exact model.
Carbon monoxide alarm
A smart addition near any gas water heater or boiler, especially when the venting has been blocked or is drawing exhaust back in.
Search eBay →Soft brush for cleaning the air filter
Handy for cleaning dust and lint off the unit's air filter.
Search eBay →Navien air pressure sensor (exact part for your model)
Technician part only. Have a qualified gas technician confirm the sensor is at fault first.
Search eBay →Sources
- Navien NR/NP series tankless water heater service manual v2.0 (2010), 5.1 Error Code List (E010 Abnormal air pressure: check vent and fresh air pipe for obstructions, check and clean air filter, check hoses and condensate drain)
- Navien NR/NP series service manual v2.0, 5.8 10Error (10 failed pre-purges then lock-out; RPM 1,000 above standard during combustion; check items: air pressure hose, venturi hole, condensate drain, exhaust inflow, rainwater in flue, sensor or PCB)
- Navien CH-180 combi boiler service manual, 5.1 Error Code List (E010 Abnormal air pressure, same three checks)
- Navien NPE-2 User's Information Manual (newer models list E110 as Abnormal air pressure; no E010 in the current table)
Last reviewed 2026-10-23. Always confirm against the manual for your exact model number.