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A.O. Smith · GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater

A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater 11 Error Fix: Ignition Failure

The unit failed to ignite after multiple attempts. No flame was detected by the flame rod after the igniter fired. Check gas supply — ensure the gas shutoff valve is fully open and other gas appliances are working. Verify the gas line is properly sized for the unit's BTU rating. Clean the igniter and flame rod with fine sandpaper. Check the igniter wire connections. Ensure the venting is not blocked — check both intake and exhaust for obstructions.

High severity2 fixes available

Quick Answer

Error 11 on the A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater means: Ignition Failure. The top-ranked community fix is “Test and Replace Igniter and Flame Rod Assembly” (hard difficulty, ~90 min, DIY cost: $20-$40). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · water heater

Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.

When to Call a Professional

While many water heater repairs can be done safely at home, consider hiring a qualified technician if:

This is a high severity error — continued use may cause damage or a safety hazard
The repair involves electrical wiring, gas lines, or refrigerant
You've tried the top-ranked fix and the error persists
You smell gas, see sparking, or notice water leaking
The repair requires specialized tools you don't have
Your appliance is still under manufacturer warranty

Average professional repair cost for this issue: $180-$250.

Other A.O. Smith Models with Error 11

ATI-540H-N 0.54 GPM 199,900 BTU High Efficiency Tankless Gas Water Heater

water_heater · 2 fixes

Other A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater Error Codes

Flame Failure

2 fixes

Combustion Abnormality

2 fixes

Overheat Protection Activated

2 fixes

Over-Temperature Warning

2 fixes

Reversed Polarity / Neutral-Ground Cross

2 fixes

Inlet Water Temperature Sensor Failure

2 fixes

Outlet Water Temperature Sensor Failure

2 fixes

Heat Exchanger Temperature Sensor Failure

2 fixes

People Also Ask About A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater Error 11

What does error code 11 mean on a A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater?

Error code 11 on the A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater means: Ignition Failure. The unit failed to ignite after multiple attempts. No flame was detected by the flame rod after the igniter fired. Check gas supply — ensure the gas shutoff valve is fully open and other gas appliances are working. Verify the gas line is properly sized for the unit's BTU rating. Clean the igniter and flame rod with fine sandpaper. Check the igniter wire connections. Ensure the venting is not blocked — check both intake and exhaust for obstructions.

How do I fix error code 11 on my A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater?

The most successful fix is "Test and Replace Igniter and Flame Rod Assembly" (hard difficulty, ~90 minutes). Estimated DIY cost: $20-$40. HomeMD has 2 community-ranked fixes for this error.

Is error code 11 on a A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater serious?

This error is rated high severity. You should address it promptly — continued use could cause damage or safety concerns.

Can I fix A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater error 11 myself?

Yes — the top-ranked community fix ("Test and Replace Igniter and Flame Rod Assembly") is rated hard difficulty and takes about 90 minutes. Tools needed: Phillips screwdriver, Multimeter, Adjustable wrench.

How much does it cost to repair A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater error 11?

DIY cost: $20-$40. Professional repair typically costs $180-$250. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater have?

The A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater has 8 other known error codes, including: 12 (Flame Failure), 13 (Combustion Abnormality), 14 (Overheat Protection Activated), 16 (Over-Temperature Warning), 29 (Reversed Polarity / Neutral-Ground Cross), and 3 more.

Which other A.O. Smith models have the 11 error?

Error code 11 also appears on 1 other A.O. Smith model: ATI-540H-N 0.54 GPM 199,900 BTU High Efficiency Tankless Gas Water Heater. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater have?

The A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater has 8 other known error codes:

12 — Flame Failure (2 fixes)
13 — Combustion Abnormality (2 fixes)
14 — Overheat Protection Activated (2 fixes)
16 — Over-Temperature Warning (2 fixes)
29 — Reversed Polarity / Neutral-Ground Cross (2 fixes)
31 — Inlet Water Temperature Sensor Failure (2 fixes)
32 — Outlet Water Temperature Sensor Failure (2 fixes)
33 — Heat Exchanger Temperature Sensor Failure (2 fixes)

Which other A.O. Smith models have the 11 error?

Error code 11 also appears on 1 other A.O. Smith model:

ATI-540H-N 0.54 GPM 199,900 BTU High Efficiency Tankless Gas Water Heater (water heater) · 2 fixes

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