Rheem Tankless Water Heater Code 11 (A011): No Ignition, Flame Not Detected (Meaning, Causes, Fixes)

What the code means

Rheem's tankless troubleshooting manual defines error 11 as Flame Not Detected by Flame Rod. When ignition fails the heater retries, and if it still sees no flame it shows 11 on the built-in display or the remote. On newer Rheem tankless models with a digital user interface the same fault shows as A011, and Rheem's training manual says those units make up to 10 ignition attempts before posting it. Rheem's SVC 820 service manual says the code is most commonly the result of gas supply and/or venting, and that a technician who finds every heater component OK still has to inspect the gas supply and venting thoroughly. The Use and Care error-code guide lists 11 together with 12 (flame loss) because the homeowner checks are the same.

Likely causes

• The gas shutoff valve to the heater isn't fully open, or gas service to the house was interrupted
• Propane running low or empty (LP models)
• Air in the gas line, common after new installation or after the gas was shut off
• Wrong gas type for the unit, or gas inlet pressure too low, often from an undersized gas line, meter or regulator. Rheem's 2008 service manual also warns that flex gas line can restrict flow enough to cause code 11
• Venting that's blocked, disconnected or not installed to the Use and Care manual
• Power supply not properly grounded
• On the technician side: an igniter rod or coil that doesn't spark, carbon buildup on the flame rod, a clogged gas inlet filter, a bad gas valve, or a failed control board

Safe DIY checks

1. Reset the way Rheem's Use and Care manual says: close the hot water faucet, turn the remote control off, wait about 5 minutes, turn it back on and open the hot water faucet again.
2. If 11 is still showing, close the faucet and turn the remote off before checking anything.
3. Make sure the gas shutoff valve to the water heater is fully open, and that other gas appliances in the house are working. If none are, contact your gas utility.
4. On propane units, check the tank level and refill or swap the cylinder if it's low.
5. Look at the vent termination outside (both intake and exhaust on direct-vent units) and clear any blockage such as leaves, snow or a nest. Don't take apart vent connectors yourself.
6. If the heater was just installed or the gas was recently off, the installer or a gas technician should bleed air from the gas line and confirm the gas type and line sizing.
7. Try the heater again. If 11 returns, write down the code, turn the remote off and call Rheem customer service or a licensed technician. Rheem's manual says not to attempt repairs to gas piping, burners, vent connectors or safety devices yourself.

Parts that commonly fix it

Always match the part number to your exact model.

Related codes

• 0 Rheem Gas Furnace 0
• E15 Bosch Dishwasher E15
• E24 Bosch Dishwasher E24
• E25 Bosch Dishwasher E25
• 24 Carrier Gas Furnace 24
• 33 Carrier Gas Furnace 33

All Rheem codes →

Sources

1. Rheem Tankless Troubleshooting Manual (files.myrheem.com): 11 Error Code, Flame Not Detected by Flame Rod (ignition retries, gas pressure ranges, gas filter, venting, igniter and flame rod checks)
2. Rheem Technical Training and Service manual (files.myrheem.com): Error A011, Flame Not Detected From Flame Rod (up to 10 ignition attempts)
3. Rheem Tankless Gas Troubleshooting Manual SVC 820 (2011): 11 Error Code, most commonly gas supply and/or venting
4. Rheem/Ruud Tankless Service Manual SVC810 (2008): Error Code 11, no ignition scenarios and flex gas line warning
5. Rheem Tankless Water Heater Use and Care manual, error code guide page 33 (reset steps, codes 11 or 12 causes and actions)