Rinnai Error Code 11: No Ignition — Meaning, Causes & Fix

No ignition — the heater ran its ignition sequence and no flame was established, so it shut down and flashed 11 on the temperature controller

Code 11 is Rinnai's no-ignition fault, and it applies across the whole tankless range this site covers: Non-SENSEI models, SENSEI models and the SENSEI RX/CX series all define 11 the same way in Rinnai's Troubleshooting Tankless Water Heater Diagnostic Codes manual. When you open a hot tap, the heater proves water flow, spins up the combustion fan, opens the gas valve and fires the spark electrode. The flame rod then has to prove flame. If no flame is proven, the controller stops the attempt, locks the burner out and displays 11 instead of the set temperature. The water runs cold, and the heater will not keep retrying on its own. Read 11 literally: ignition was attempted and failed. That separates it from its nearest neighbours. Code 12 means a flame WAS established and then went out during operation. A heater with no code at all has usually not even started its sequence — flow too low, lines crossed, or a clogged inlet filter — which Rinnai documents separately under its 'No Code' troubleshooting. Code 11 sits between those two states: the machine tried, and the try failed. Rinnai's own remedy list for 11 is dominated by the gas supply, and that ordering is deliberate. The manual works through: gas turned on at the heater, meter or cylinder; propane actually in the tank; air purged from the gas lines; correct gas type; inlet gas pressure correct with the minimum on the rating plate maintained while every gas appliance at the site fires on high fire; and the gas line, meter and regulator sized properly. Only after the supply is proven does the procedure move inside the cabinet — igniter operation and wiring, gas solenoid valves checked for open or short circuits, burners seated, the burner plate inspected for condensation or debris, and the PC board ground wire. A loose flame rod — Rinnai calls it a 'floating' flame rod — is named as a cause of both 11 and 12, because a rod that cannot sit correctly in the flame cannot prove it. Two framing points matter before anyone touches anything. First, Rinnai's manuals reserve the internal half of this diagnosis for licensed professionals: gas pressure measurement with a manometer, solenoid testing and burner removal are not owner tasks. Second, if you smell gas at any point, the manual's instruction is absolute — do not light anything, do not touch electrical switches, leave and call your gas supplier from outside; if you cannot reach them, call the fire department. Code 11 with a gas smell is not a troubleshooting session. What an owner can legitimately establish is the external story: whether other gas appliances work, whether a propane tank is empty or a meter valve was closed after other work, whether the failure started right after a gas interruption or a tank change (air in the line is a classic post-installation 11), and whether the vent termination outside is visibly blocked. That story, plus the exact code, is what the technician needs — and it is often the difference between a supply fix and a parts bill.

What causes the 11 code on a Rinnai water heater?

Gas off, empty, or never purged

The commonest 11 story in Rinnai's list is embarrassingly basic: a shutoff valve closed at the heater or meter, an empty propane cylinder, or air still in the gas line after installation or a tank change. The heater's sequence runs perfectly and simply has nothing to burn. Owners can verify valves and tank contents; purging a gas line is professional work. It is also the first code a new installation earns when a final valve check was skipped, which is why installers treat a first-day 11 as a commissioning check rather than a breakdown.

Undersized or weak gas supply

A tankless heater is the largest gas load in most homes. If the line, meter or regulator cannot hold the rating-plate minimum inlet pressure while everything fires on high fire, ignition fails or will not sustain. Rinnai quantifies the check: no more than about 0.3 in. water column pressure drop on natural gas (0.5 in. on propane) with all appliances at high fire. This is manometer work for a licensed gas technician. Tankless heaters expose weak gas infrastructure that tank heaters tolerated for years, because their burners demand far more gas in far less time.

Wrong gas type or wrong settings

A natural-gas heater fed propane (or the reverse), a gas-type DIP switch or SENSEI Parameter 10 set for the other fuel, or wrong altitude settings all prevent proper ignition. Rinnai repeats the gas-type check in nearly every ignition procedure because a conversion or board replacement done carelessly surfaces first as an 11. The rating plate on the side of the unit, not the paperwork for a different appliance, is the authority for which fuel the heater expects. It is also why a board replacement finished without the parameter check so often introduces itself as an ignition fault.

Igniter or flame rod fault

The spark electrode must spark with the correct gap — 0.138 in. (3.5 mm) on SENSEI procedures — and the ceramic electrode and flame rod must be tight in their bracket. Carbon or a white substance coating the flame rod, a damaged igniter harness, or a loose 'floating' rod that drops toward the burners all break flame proof even when gas and spark are present. Rinnai even colour-codes the flame-rod wiring on multi-rod models (stamped Y, R and B on the bracket) because a rod wired to the wrong terminal produces exactly this code.

Gas solenoid, burner or board fault

The last group is internal: gas solenoid valves with open or short circuits, burners displaced from their seats (Rinnai notes a dropped heater can shift them), condensation or debris on the burner plate, a moisture-damaged gas valve, or a PC board that will not drive the valve. These are proven by measurement, in order, by a licensed technician — not by replacing parts in sequence. The manual's discipline is to exhaust supply, spark and flame-proof evidence first, because boards and valves replaced on suspicion usually return as repeat visits.

Checks to run before you replace anything

1. Write down the code exactly as displayed, and note whether the fan ran and whether you heard sparking before it appeared — that tells the technician how far the sequence got
2. Check the obvious supply points: gas shutoff at the heater open, meter valve open, and on propane, gas actually in the tank
3. Check whether other gas appliances in the building work normally; a whole-house outage is a utility problem, not a heater problem
4. Look at the outdoor vent termination from outside: snow, nests, mulch or a blocked flue outlet stop ignition and are owner-visible
5. Note the timing: a first-ever 11 right after installation, a tank change or gas work points at air in the line or sizing; a new 11 on an old heater points elsewhere
6. Use the fault history before resetting: hold ON/OFF for 2 seconds, then press UP — the last 9 codes flash in order, and earlier 12s, 10s or LCs change the diagnosis
7. Smell check: if there is any smell of gas, stop here — no reset, no switches, leave and call the gas supplier from outside

Rinnai error code 11 fix

1. Owner step 1: correct anything external you found — open the closed valve, arrange a propane refill — then make ONE reset attempt (controller OFF then ON, or taps off then on) and run a hot tap
2. If the heater lights and holds, watch it through a full hot-water draw; a single 11 after a gas interruption that does not return is the documented air-in-the-line pattern
3. If 11 returns immediately, stop resetting. Repeated ignition attempts on a gas fault are not a fix, and Rinnai's procedure from here is measurement, not repetition
4. Technician stage 1: prove the supply — inlet pressure at high fire with all appliances firing, gas type against the rating plate, DIP switch or Parameter 10, and line/meter/regulator sizing
5. Technician stage 2: prove ignition hardware — spark test, electrode gap and tightness, flame rod condition and correct colour-coded wiring, solenoid resistance/voltage at the board
6. Technician stage 3: burner and board — burners seated, burner plate clean and dry, heat-exchanger fins clear, then gas valve or PC board replacement only as the measurements indict them

The part that usually fails: Igniter / spark electrode and flame rod assembly (with its gasket)

When a part is genuinely at fault on an 11, it is most often in the ignition-proof pair: the spark electrode that lights the burner and the flame rod that proves the flame. Rinnai's procedure is specific about their service rules — both must sit tight in the mounting bracket, the electrode gap is set (3.5 mm on SENSEI), carbon or white build-up is cleaned off, and the electrode/flame-rod gasket MUST be replaced if the seal is broken during removal, so a technician will have a new gasket in hand before opening the assembly. A gas valve follows only when solenoid measurements fail.

Rinnai error code 11 reset button

Rinnai's owner-level reset for an ignition fault is a controller cycle: turn the temperature controller OFF, then ON again (the bath-fill code 03 procedure — OFF/ON twice — is the same family), or turn all hot taps off and back on, then run one hot tap and watch a full ignition attempt. On older Non-SENSEI units a power off-and-on at the supply also clears the display. One attempt is the rule. If 11 comes straight back, the fault is live — the heater is correctly refusing to light, and the next step is the technician sequence, not a second or third reset. Never reset repeatedly through a gas smell.

The standard owner reset is a controller cycle: close the hot taps, press ON/OFF to turn the controller off, then on again, and run one test draw (code 03's documented form is ON/OFF twice). Special codes have special resets that are not interchangeable: LC and SS use five ON/OFF presses within five seconds (LC's version is a 70-hour temporary reprieve, not a cure); codes 17 and 52 clear only through the PC-board A/B-button sequence ending in 'ECL'; codes 57 and 58 need a hard reset — power off, then on — after the cause is corrected; and the LC hard reset after flushing is the A/B switches held together for five seconds. One reset, then observe: a code that returns is a live fault reporting itself, not a reset that 'didn't take'. Document the outcome of every reset you perform — cleared and held, returned during the draw, or never cleared — because that record is what turns a home reset into diagnostic evidence.

Why does the 11 code keep coming back?

An 11 rarely travels alone, and the fault history is the cheapest diagnostic on the unit. A history that shows 10 before the 11 points at the vent system starving combustion air. Repeated 12s before the first 11 suggest a flame-proof problem that has now become total. LC stored as 00 points at a scaled heat exchanger that has been run on temporary resets — a heater in that state needs its flush, not just an ignition repair. Read the history (hold ON/OFF two seconds, then UP) before the display is cleared, and quote the whole sequence when you call.

How to stop 11 coming back

• Gas off, empty, or never purged: The commonest 11 story in Rinnai's list is embarrassingly basic: a shutoff valve closed at the heater or meter, an empty propane cylinder, or air still in the gas line after installation or a tank change. The heater's sequence runs perfectly and simply has nothing to burn. Owners can verify valves and tank contents; purging a gas line is professional work. It is also the first code a new installation earns when a final valve check was skipped, which is why installers treat a first-day 11 as a commissioning check rather than a breakdown.
• Undersized or weak gas supply: A tankless heater is the largest gas load in most homes. If the line, meter or regulator cannot hold the rating-plate minimum inlet pressure while everything fires on high fire, ignition fails or will not sustain. Rinnai quantifies the check: no more than about 0.3 in. water column pressure drop on natural gas (0.5 in. on propane) with all appliances at high fire. This is manometer work for a licensed gas technician. Tankless heaters expose weak gas infrastructure that tank heaters tolerated for years, because their burners demand far more gas in far less time.
• Wrong gas type or wrong settings: A natural-gas heater fed propane (or the reverse), a gas-type DIP switch or SENSEI Parameter 10 set for the other fuel, or wrong altitude settings all prevent proper ignition. Rinnai repeats the gas-type check in nearly every ignition procedure because a conversion or board replacement done carelessly surfaces first as an 11. The rating plate on the side of the unit, not the paperwork for a different appliance, is the authority for which fuel the heater expects. It is also why a board replacement finished without the parameter check so often introduces itself as an ignition fault.

Retrieving stored fault codes on Rinnai water heaters

Rinnai tankless heaters report faults on the temperature controller — the integrated SENSEI controller or a remote such as the MC-91-2 or MC-601 — as flashing two-digit codes in place of the set temperature. Alongside the numbers sit four letter displays with their own jobs: LC (scale in the heat exchanger, counted as LC0–LC9 when temporary resets are used, and stored as 00 in the fault history), SS (the time-based Service Soon reminder, also shown as 55), FF (a history placeholder recording that maintenance was performed) and, on cascaded commercial systems only, SE. The controller keeps a fault history: turn the heater OFF, hold ON/OFF for 2 seconds and press UP at the same time — the last 9 maintenance codes flash one after the other. A separate performance-data mode (hold DOWN, then ON/OFF) shows live values such as water flow rate (item 01) and outgoing temperature (item 02) — data items, not fault codes.

Other Rinnai water heater error codes

See the full list on the Rinnai Water Heater error codes hub.

Codes 11 gets confused with

12 — Flame failure — the burner lit, then the flame was lost during operation and the heater shut down Code 12 is the running partner of code 11, and the distinction is the whole diagnosis.

10 — Air supply or exhaust blockage — on SENSEI condensing models the same code also reports a full condensate trap Code 10 is Rinnai's airflow fault: the heater cannot move combustion air in and exhaust out the way it needs to, so it shuts down and displays 10.

17 — Venturi blockage — debris is obstructing the venturi on the gas valve/fan assembly (SENSEI and SENSEI RX/CX only) Code 17 is one of Rinnai's narrowest codes: it exists only on SENSEI and SENSEI RX/CX models, and it means exactly what its title says — venturi blockage.

LC — Scale build-up in the heat exchanger — the heat exchanger must be flushed; LC0–LC9 count how many 70-hour temporary resets have been used without a flush LC is the code Rinnai owners in hard-water areas know best, and it is a maintenance alarm rather than a breakdown.

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Facts on this page were checked against manufacturer documentation: www.rinnai.us · media.rinnai.us · www.rinnai.ca · media.rinnai.us · www.manualshelf.com · www.rinnai.us