🚿Water Heater

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 16 Error Fix: Over-Temperature Warning

The outgoing water temperature has exceeded the set temperature by more than the allowable threshold. The unit will shut down to prevent scalding. This can be caused by low water flow rate, high inlet water temperature, scale buildup in the heat exchanger reducing flow, or a malfunctioning water flow control valve. Check the inlet filter screen for debris. Flush the heat exchanger with a descaling solution. Verify the water flow rate meets minimum requirements.

High severity2 fixes available✨ Free fix available

Quick Answer

Error 16 on the A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater means: Over-Temperature Warning. The top-ranked community fix is “Flush Heat Exchanger and Inspect Water Flow Control Valve” (medium difficulty, ~60 min, DIY cost: $15-$20). 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: $220-$350.

Other A.O. Smith Models with Error 16

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

Ignition Failure

2 fixes

Flame Failure

2 fixes

Combustion Abnormality

2 fixes

Overheat Protection Activated

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 16

What does error code 16 mean on a A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater?

Error code 16 on the A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater means: Over-Temperature Warning. The outgoing water temperature has exceeded the set temperature by more than the allowable threshold. The unit will shut down to prevent scalding. This can be caused by low water flow rate, high inlet water temperature, scale buildup in the heat exchanger reducing flow, or a malfunctioning water flow control valve. Check the inlet filter screen for debris. Flush the heat exchanger with a descaling solution. Verify the water flow rate meets minimum requirements.

How do I fix error code 16 on my A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater?

The most successful fix is "Flush Heat Exchanger and Inspect Water Flow Control Valve" (medium difficulty, ~60 minutes). Estimated DIY cost: $15-$20. HomeMD has 2 community-ranked fixes for this error.

Is error code 16 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 16 myself?

Yes — the top-ranked community fix ("Flush Heat Exchanger and Inspect Water Flow Control Valve") is rated medium difficulty and takes about 60 minutes. Tools needed: Phillips screwdriver, Adjustable wrench, Descaling pump, Multimeter.

How much does it cost to repair A.O. Smith GT15-340-NI Commercial 340,000 BTU Commercial Natural Gas Water Heater error 16?

DIY cost: $15-$20. Professional repair typically costs $220-$350. 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: 11 (Ignition Failure), 12 (Flame Failure), 13 (Combustion Abnormality), 14 (Overheat Protection Activated), 29 (Reversed Polarity / Neutral-Ground Cross), and 3 more.

Which other A.O. Smith models have the 16 error?

Error code 16 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:

11 — Ignition Failure (2 fixes)
12 — Flame Failure (2 fixes)
13 — Combustion Abnormality (2 fixes)
14 — Overheat Protection Activated (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 16 error?

Error code 16 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

Ad Space — banner

Replace ADSENSE_PUBLISHER_ID in AdUnit.tsx