What does Rinnai error code 11 mean?

Code 11 means the burner failed to ignite. When you open a hot water tap, a Rinnai fan starts, a spark igniter fires, and the gas valve opens. A flame rod then has to confirm a flame. If it never confirms one, the heater shuts the gas off and flashes 11 on the controller. That shutdown is a safety feature doing its job.

So code 11 is not a single broken part. It is a symptom with three families of cause: no gas reaching the burner, no spark, or a flame the heater cannot detect. Rinnai's service steps work through all three, and so will you.

Start with the gas smell test, then the easy items. Rinnai's manual opens with a safety rule: if you smell gas, do not try to light anything, do not touch electrical switches, and do not use a phone in the building. Leave and call the gas company. In the Phoenix area that is Southwest Gas at 877-860-6020, plus 911 from a safe distance. The utility says to leave doors open on your way out and to skip switches, thermostats and garage door openers. A gas smell always beats a diagnostic code.

If there is no gas smell, these are the checks that are safe for a homeowner:

1. 1Gas valve. Confirm the shutoff valve on the gas line to the heater is fully open. Rinnai lists this as the first check. A valve nudged by a stray elbow or shut for other work is a classic cause.
2. 2Other gas appliances. If the range or furnace also acts up, the problem is upstream of the heater, at the meter or the house piping.
3. 3Propane tank. On propane, make sure the tank actually has fuel. Rinnai also says the tank has to be properly sized for the load.
4. 4Recent gas work. After a new install or a gas line repair, air trapped in the pipe can cause a code 11 until it is purged. Rinnai lists this as a check too.
5. 5Power off and on. Turn the heater off at its controller, wait a minute, then turn it back on and run a hot tap. Rinnai's own manual uses that power off and on step to see whether a code clears.

If the heater lights and runs normally afterward, it may have been a one-time hiccup. Note the date. Code 11 that returns in a few days is a real fault.

When the valve is open and the tank is full, the cause is usually inside the heater or in the gas supply. Rinnai's service manual lists these, roughly in the order a technician checks them:

• Low inlet gas pressure. The heater has a minimum gas pressure, printed on its rating plate, that must hold while it fires on high. Undersized gas pipe, a regulator, or a shared line with other appliances can drop it. Rinnai says the drop should be no more than 0.3 inches of water column on natural gas with every gas appliance in the building firing.
• Wrong gas type. The unit's gas type has to match the supply. Rinnai has a setting and a red or blue orifice that must be right for propane or natural gas.
• No spark. A cracked or loose igniter gives a click with no flame. The spark gap should measure 3.5 millimeters, about 0.138 inch.
• Dirty flame rod. Carbon or a white crust on the flame rod keeps it from sensing a flame that is really there. A loose rod, which Rinnai calls a floating flame rod, causes the same code.
• Vent problems. Vent joints that leak, or a vent terminal too close to a wall or obstruction, can recirculate exhaust into the intake and foul the flame.
• A clogged burner or gas valve. Debris in the burner orifices, insects in the burner chamber, or a valve that sticks now and then.
• Damp wiring. Moisture in the electrical connections can make the ignition circuit act up.

Most of that list is for a technician. Rinnai's manual says it is written for trained, qualified professionals, and that is worth taking seriously because the steps involve live voltage and gas.

A reset is just turning the heater off and on again. Use the on and off button on the controller, wait about a minute, then turn it back on and open a hot tap. Rinnai's manual also describes viewing the last nine codes from the controller, which helps a technician see whether 11 is a repeat visitor.

Do not keep hitting reset all day. The reset clears the display, not the cause. If code 11 comes back after two or three tries, the heater is telling you something is wrong with the gas, the spark or the flame sensing. Repeated failed ignition attempts are also a good reason to stop and let someone measure things.

### What should I leave to a licensed plumber?

Anything that involves opening the gas system or the burner compartment. That includes checking gas pressure with a manometer, pulling the igniter and flame rod, cleaning the burner, and testing the gas valve solenoid. Rinnai's manual puts it plainly: gas system sizing and troubleshooting belong to a professional gas technician or master plumber.

There is one more reason to hand it off. Some of the fixes involve replacing gaskets that must not be reused, and setting the gas type and altitude on the control board. A wrong setting can create a fresh problem that looks like code 11 all over again.

HQ Plumbing and Air is licensed and insured, offers 24/7 emergency service, and gives free estimates and upfront pricing before work starts. If code 11 keeps coming back and you have no hot water, that is the time to call.

### Can code 11 mean the heater is dying?

Sometimes. Code 11 alone does not mean the heater is finished. Most items on Rinnai's list are a cleaning, an adjustment, a single part or a gas supply fix. The exceptions are a cracked heat exchanger, which Rinnai flags when liquid drains from the condensate line while the unit is not running, and a failed control board after other parts have been ruled out.

If the heater is old and the code keeps returning after repairs, read our guide on whether to repair or replace a water heater. Tankless units also need regular flushing in Phoenix, where the water is hard. Our page on descaling a tankless water heater in Phoenix explains how often. Scale is a separate problem from code 11, but a heater that is neglected tends to collect several problems at once.

Rinnai uses different numbers for different failures, and they are easy to mix up:

• Code 11 is no ignition. The burner never lit.
• Code 12 is flame failure. The burner lit, then the flame went out or could not be sensed. See our page on Rinnai error code 12.
• Code 10 is an air supply or exhaust blockage, or a full condensate trap. See our page on Rinnai error code 10.

Rinnai notes that a loose flame rod can produce either code 11 or code 12, so a technician often treats them as neighbors. If you see one code followed by the other, that tells them to look hard at the flame rod and the gas supply.

### What to do next

Check for gas, confirm the valve and the propane tank, power the heater off and on once, and note whether it lights. If it does not, or the code returns, stop and call for service. That is the fix, and it is a short one.

A Rinnai that lights and then runs hot enough to trip a safety device shows a different code, covered on our page on Rinnai error code 14.

Noritz owners with a code 11 can read our page on Noritz error codes 11, 90 and 99.