Water heater locks out with E02 on display, burner does not ignite, circulator may run briefly then stop.

Safety first: Turn off power to the Triangle Tube water heater at the service switch and close the gas shutoff valve before touching any gas components. Allow the unit to cool.

• 1. Reset and observe: Restore power, open the gas valve, and attempt a reset from the control panel. Watch through the sight glass: you should see sparking and then flame. If E02 returns after several tries, continue below.
• 2. Check gas shutoff and supply: Verify the manual gas shutoff valve to the heater is fully open. Confirm other gas appliances in the home work normally. If you suspect low gas pressure, stop and call your gas supplier or a licensed technician.
• 3. Inspect ignition electrode: With power and gas off, remove the burner access cover. Locate the ignition electrode assembly. Check for cracked porcelain, heavy carbon buildup, or loose wiring. Clean the electrode tip gently with fine emery cloth and ensure the gap and position match the Triangle Tube service manual.
• 4. Clean flame sensor: Many Triangle Tube burners use a combined ignition/flame rod or a separate flame sensor. Remove the flame sensor rod and gently clean it with fine steel wool or emery cloth until shiny. Reinstall firmly and reconnect the wire.
• 5. Check wiring to gas valve and ignition module: Inspect the harness from the main control board to the gas valve and ignition transformer/module. Look for loose plugs, corrosion, or damaged insulation. Reseat all connectors.
• 6. Inspect burner and combustion chamber: Remove the burner assembly if accessible. Vacuum out dust and debris from the burner head and combustion chamber. Do not enlarge or poke burner ports with hard tools.
• 7. Test operation: Reassemble, restore gas and power, and attempt ignition. If E02 persists, the gas valve, ignition transformer, or control board may be defective.
• 8. When to call a professional: If you do not have a manometer to verify gas pressure or are not trained to work on gas valves and combustion, contact a qualified Triangle Tube service technician. Do not continue cycling the unit in lockout.