Rinnai code 12 means the heater lost or never found its flame. Check that the gas valve is open, the propane tank is not empty and the vent outlet is clear. Rinnai marks most other fixes licensed professional only, so call a technician.
Having an issue with your Rinnai water heater displaying error code 12? For every other code, see our full Rinnai error code list, with code 11 and code 10 on their own pages.
Rinnai files code 12 under flame failure: the burner did not light or the flame went out, most often because of the gas supply or pressure, a dirty flame rod, or blocked venting and air intake. Rinnai’s current diagnostic code guide covers codes for all its tankless models.
A few of the checks are simple and safe for a homeowner: the gas valve, the propane tank and the vent outlet. Most of the rest involve gas or electrical parts, and Rinnai’s own code 12 list marks them licensed professional only. This guide separates the two.
We’ll cover what to look at yourself, what the usual causes are, and what a technician will do.
Rinnai Error Code 12 Indicators
Here are a few telltale signs to look for when the Rinnai error code 12 pops up:
Flashing Code 12 Signals Flame Failure
The Rinnai control panel displaying a flashing 12 code means the unit could not light or keep its flame, so the water is not heating. Rinnai’s first checks are the gas supply at the heater and the meter, then the flue and air intake for obstructions.
No Hot Water Due To Restricted Airflow
Restricted airflow is a common cause of a Rinnai heater providing little or intermittent hot water. A clogged air filter, debris blocking the PVC intake vent, or broken fan can choke airflow, preventing the burners from igniting correctly.
Odd Noises from Strained Fan
If you hear rattling, grinding, or humming sounds from your water heater, something’s off. Maybe dust has built up and is clogging the fan blades, so the motor strains to spin. Or debris could be stuck in the fan. Either way – the airflow suffocates. A rattling or grinding fan is worth mentioning to the technician.
Gas Odor Signals Danger
If you smell gas, treat it as an emergency, separate from the error code.
Leave the building. Rinnai’s manual says: do not try to light any appliance, do not touch any electrical switch, do not use any phone in your building, call your gas supplier from a neighbor’s phone and follow its instructions, and call the fire department if you cannot reach the supplier. Do not go back in to troubleshoot.
Understanding Error Code 12: Root Causes
When error 12 pops up, it generally boils down to the gas supply, the venting and air, or the flame rod and electrical parts that detect the flame. Let’s unpack some specifics.
1. Gas Related Issues
Rinnai lists code 12 as flame failure (no flame detected) and lists code 11 separately as no ignition. Not enough gas or air is the most common reason.
On the gas supply side, loose pipe fittings, incorrect line pressure, or using the wrong fuel type can starve the flames. Airflow issues like a dusty filter or blocked vents have a similar effect, choking off the oxygen.
Without enough fuel and air to sustain combustion, the burners will not stay lit, and the heater shows code 12.
2. Combustion Related Issues
Code 12 can also come from the combustion side, beyond the fuel and air supply.
Rinnai’s checklist includes burners that are not seated properly or have condensation or debris on the burner surface, a loose spark electrode or flame rod, and a blower wheel with debris or insects in it. All of these are technician checks.
3. Sensor Related Issues
Sensor issues can also shut down your Rinnai’s heating and display error code 12, disrupting your hot water. For example, flame sensors verify burner ignition but get coated in grime over time, preventing proper detection.
Rinnai also lists a disconnected flame rod wire, a cracked flame rod sleeve and a poor ground connection as causes. On SENSEI models, a code 12 that appears the moment water starts to flow points to an electrical short in a part such as the water flow control or bypass valve.
When these vital updates about burner status or heating demand can’t get through properly, the unit assumes something is wrong and halts operation.
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Troubleshooting Steps for Resolving Error Code 12
Step 1: Preliminary Checks
First, we must run through some basic checks before inspecting the unit up close.
Verify the Water and Fuel Supply
Check that the water lines are turned on and faucets are open – cold water should flow freely even if hot water isn’t working.
Make sure the gas supply valve is fully open, too. If the heater runs on propane, check that the tank is not empty. Measuring gas pressure is a job for a licensed gas technician, not a homeowner.
A gas line that is too small for every gas heater firing at once can also drop the pressure and trigger the code, which a technician can measure.
Check the Display and Power
Make sure the heater has power and its display is lit.
Rinnai’s manual says the error code keeps flashing until the problem is corrected and the water heater supplies hot water.
Check for External Damage
Walk around the unit, checking for broken, bent, or damaged parts. Rodents nesting in vent pipes or debris in the intakes can quickly cause system errors.
These preliminary checks help narrow down potential causes of error 12 before troubleshooting the unit’s internal components.
Step 2: Basic Troubleshooting
Double Check Gas Supply and Valves
Now that we’ve verified the external factors are all working properly let’s take a closer look at the gas supply flow. Checking that the incoming gas pressure matches the unit’s rating plate takes a manometer and training, so leave it to a licensed gas technician.
Pressure that’s too high or low could be triggering the error code. Also, check that all manual gas valves leading to the unit are fully open. Even partially closed valves can restrict flow enough to cause problems.
Bleeding air out of the gas lines is technician work too: Rinnai lists it among the steps marked licensed professional only.
Reset Error Codes
With the gas valve open, turn the heater off with its On/Off button, wait a moment and turn it back on, then open a hot tap. Rinnai’s list of fixes for code 12 does not include a reset step, because the code clears once the cause is corrected. If it comes back, the cause is still there, so stop resetting and move on.
Check and Clean Debris
Look at the outside of the unit and the vent outlet for debris, snow, leaves or nests that could block the air intake or exhaust, and clear them from the ground.
Do not open the cabinet. Rinnai’s manual says to cut electricity, gas and water before any maintenance, and its code 12 checks for the blower, burners, gas valve and flame rod are marked licensed professional only.
Inspect the Gas Valve Condition
Look at the gas valve and visible pipes for damage, but do not tighten fittings or replace valves yourself. If you smell gas, leave the building and call your gas supplier from outside. Any gas repair needs a licensed plumber or gas technician.
Step 3: Advanced Troubleshooting
At this stage, the problem requires advanced diagnostics and troubleshooting, best carried out by a trained Rinnai technician.
Further tinkering without expertise risks compounding issues or voiding guarantees. Here are professional-grade steps a seasoned pro would execute:
Inspecting Flame Rods & Wiring
A professional removes and carefully inspects the flame rod and its wiring. They check for small dirt buildup that might affect burner detection, as well as heat damage that could have weakened connections. This guides rod cleaning or replacement. Rinnai’s checklist also has them look at the flame rod’s silicone sleeve for cracks, the vent joints for loose fittings that let exhaust gas circulate back into the unit, and the ground connections.
Comprehensive Sensor Testing
Technicians use advanced tools to test each sensor and validate they are transmitting proper data to control modules.
They check ignition sequences as well for any faults. This ensures sensors or software logic issues are truly ruled out before assuming replacement parts are needed.
It might be tempting to keep trying to fix the issue yourself, but complex heating systems have subtleties that are tough to spot without the proper training.
Instead of getting frustrated or risking mistakes, it’s best to work with a certified Rinnai professional at this point.
When to Call Professional Service
DIY troubleshooting goes a long way, but certain situations demand professional expertise:
- If you smell gas or suspect a leak, leave the building and call your gas supplier or the fire department from outside. If you spot severe damage, shut the unit down and schedule certified service. Don’t try to fix gas pipes on your own.
- If error 12 persists after comprehensive DIY steps, the underlying issues probably need advanced diagnostics tools and technical knowledge. Any complex disassembly also requires certified technicians to retain your warranty coverage.
- If you don’t feel comfortable or sure about working with electricity, gas lines, ignition sequences, or sensors, it’s time to call a professional. Don’t take shortcuts with heating systems.
Locating Certified Rinnai Technicians
Seeking professional service starts with finding certified technicians familiar with Rinnai systems. Rinnai’s Find a PRO tool at rinnai.us/find-pro lists professionals near you.
Ask any technician you hire whether they service Rinnai heaters and hold the gas and plumbing licenses your state requires.
Visit this page to request estimates from local technicians.
Knowing when to tap a professional and where to find certified experts ensures error 12 gets resolved promptly and safely.
Preventing Future Error Code 12 Occurrences
Resolving the immediate code is a priority, but we also want to minimize repeat issues. Here are pro tips to avoid recurring error code 12:
1. Preserve Proper Airflow Clearances
Ensure the area around the installed unit meets the minimum clearance requirements outlined in Rinnai manuals.
Blocking ventilation openings or adding enclosures limits air supply to the fan and burners, leading back to code 12.
2. Schedule Annual Maintenance Checks
Routine maintenance tunes up key components and detects issues before they cascade into shutdown errors.
Have a licensed professional inspect the heater every year, which Rinnai’s manual requires. Cleaning the inlet water filter is a listed maintenance item, and Rinnai says the heat exchanger should be flushed periodically by a professional installer.
3. Keep Air Paths Obstruction-Free
Ensure the exterior PVC air intake and exhaust terminal remain debris and snow-free year-round.
Clogged pathways are prime culprits of limited airflow and subsequent fault codes. Periodically inspect terminals and remove any buildup.
4. Consider Service Plans
Preventative maintenance plans provide regular system analysis, cleaning, and discounted rates for any repairs needed over time.
A service plan can reduce repeat visits, but compare what it covers before you buy. But when issues pop up, use the outlined troubleshooting tips and contact certified support to resolve problems promptly.
Content writer and HVAC expert. Erica has written HVAC content and features for Forbes, My Domaine, U.S. News and The Spruce.