Ruud 12 Error Code

What does Ruud 12 mean?

On Ruud RUTGH condensing tankless water heaters, error code 12 means the gas shut-off valve is not fully opened. The unit needs full gas supply to fire the burner; when gas flow is restricted because the manual gas valve is partly or fully closed, the controller cannot establish combustion and displays code 12.

Symptoms

• 12 shown on the remote control LED display
• Burner does not ignite
• No hot water
• Heater attempts to start then faults out

Common causes

• Manual gas shut-off valve not fully opened
• Gas valve partially closed during service or installation
• Restricted gas supply to the unit

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Diagnostic steps

1. Locate the manual gas shut-off valve

   Find the gas shut-off valve on the gas line serving the water heater.

2. Check and open the valve completely

   The manual's solution for code 12 is to check the shut-off valve and open it completely so the unit receives full gas flow.

3. Restart the heater

   Turn off the faucets, turn the heater off, then turn on a hot water faucet and recheck the display. If it persists, unplug for about 30 seconds, plug back in, restart, and recheck.

4. Call for service if the code remains

   If 12 is still displayed with the gas valve fully open, note the code and contact a qualified service technician.

When to call a professional

If opening the gas shut-off valve fully does not clear code 12, call a qualified service technician. The manual warns, for your safety, not to attempt repair of gas piping, burners, or other safety devices, and to refer those repairs to a qualified service technician. Do not attempt to find the cause of a gas problem yourself if you suspect a leak.