Rinnai tankless water heater code 11: no ignition

By Jason Dearmin · Last reviewed November 14, 2026 · How we check facts

What code 11 means

In Rinnai's diagnostic code guide, code 11 is No Ignition, and it applies to SENSEI, SENSEI RX/CX and non-SENSEI models. The unit tries to light and fails. Because the same code 11 is also described by the flame rod circuit, the cause can be fuel supply, ignition, or flame sensing.

Rinnai's first checks (supply side)

• Verify all gas valves on the system are open.
• If the system runs on propane, make sure there is gas in the tank (and that the tank was properly sized).
• Verify all air was purged from the gas lines after installation (this mostly matters after new gas work).
• Verify the inlet gas pressure matches the rating plate on the side of the heater, with all gas appliances firing on high.
• Verify the gas supply type matches the gas type listed on the water heater.

Settings and parts checks (technician)

Rinnai also lists these for a trained technician: confirm the gas type setting (on SENSEI models, Parameter 10: A is natural gas and B is propane; on non-SENSEI models, the gas type DIP switch on the PC board), confirm the igniter produces a spark, and check the spark electrode gap of 0.138 in (3.5 mm). The ceramic sparker electrode and flame rod should be tight in the mounting bracket, and a loose one can lead to a code 11 or 12.

On SENSEI RX/CX models, Rinnai notes that Parameter 10 (gas type) can only be changed within 20 minutes after resetting power. A wrong gas type setting is a classic cause of a new or converted installation never lighting.

What a homeowner can do

Check that the gas shutoff valve at the heater is open and that other gas appliances are working. If you use propane, look at the tank gauge, because winter demand empties tanks faster. If the supply seems normal, stop and call a technician.

Safe homeowner checks for Rinnai code 11

1. Check the gas shutoffMake sure the gas valve feeding the water heater is open (the handle in line with the pipe).
2. Check propane levelIf you use propane, check the tank gauge and have it refilled if it is low.
3. Try another gas applianceIf a gas range or furnace also fails to light, call your gas utility or propane supplier.
4. Reset onceTurn the heater off and on again once. If code 11 returns, call a gas technician.

Frequently asked questions

Is code 11 the same as code 12?

No. Rinnai lists 11 as no ignition (the flame never appears) and 12 as flame failure (a flame appears and is lost). Some causes overlap, such as loose electrode or flame rod.

Could code 11 be a propane problem?

Yes. Rinnai asks you to verify that the propane tank has gas, and that the heater is set to propane. An empty tank or the wrong gas type setting prevents ignition.

Sources

• Troubleshooting Tankless Water Heater Diagnostic Codes (Rinnai America) Covers: Rinnai tankless water heaters in the SENSEI, SENSEI RX/CX and non-SENSEI series. Not every code applies to every model.

Safety note: this page is general information drawn from the sources above. Gas, combustion and line-voltage repairs belong to a licensed professional. Your own equipment's label and manual take priority over anything here. Read the full disclaimer.