Rinnai Rinnai RE180iN RE Series Non-Condensing Tankless Water Heater 05 Error Fix: Blocked Exhaust / Air Supply

Error code 05 on the Rinnai Rinnai RE180iN RE Series Non-Condensing Tankless Water Heater means: Blocked Exhaust / Air Supply. The unit has detected restricted combustion air intake or exhaust venting. Rinnai tankless water heaters require proper venting to supply combustion air and exhaust combustion gases safely. Error 05 indicates the air pressure switch or combustion air sensor has detected insufficient airflow. The most common cause is a blocked or partially obstructed vent termination — birds nesting in the vent cap, leaves or debris covering the intake, ice or snow buildup in winter, or a screen on the vent cap that has become clogged with lint and spider webs. Also check for collapsed or kinked vent pipe sections, excessive vent length exceeding the maximum allowed for the model, and inadequate clearances at the vent termination. For direct-vent (two-pipe) installations, check both the intake and exhaust pipes. On power-vent models, verify the blower is operating correctly. Clear all obstructions and verify vent pipe total length and number of elbows comply with the installation manual specifications.

The most successful fix is "Inspect and Replace Combustion Air Pressure Switch or Blower" (medium difficulty, ~60 minutes). Estimated DIY cost: $10-$30. HomeMD has 2 community-ranked fixes for this error.

This error is rated warning severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Yes — the top-ranked community fix ("Inspect and Replace Combustion Air Pressure Switch or Blower") is rated medium difficulty and takes about 60 minutes. Tools needed: T20 Torx screwdriver, Multimeter, Adjustable wrench.

DIY cost: $10-$30. Professional repair typically costs $300-$450. Many homeowners save money by trying the top-ranked community fix first.

The Rinnai Rinnai RE180iN RE Series Non-Condensing Tankless Water Heater has 8 other known error codes, including: 02 (Ignition Failure), 03 (Bath Fill Function Abnormality), 10 (Blocked Exhaust — Air Pressure Switch), 11 (No Ignition), 12 (Flame Failure), and 3 more.

Error code 05 also appears on 8 other Rinnai models: Rinnai RL75iN RL Series Tankless Water Heater, Rinnai RL94iN RL Series Tankless Water Heater, Rinnai RSC160iN Condensing Combi Boiler, Rinnai RU130iN Sensei Super High Efficiency Plus Tankless Water Heater, Rinnai RU199iN Sensei Super High Efficiency Plus Tankless Water Heater, Rinnai RUR199iN Sensei Recirculating Tankless Water Heater, and 2 more. The fix may vary by model, so check each model's specific page for tailored repair steps.