A.O. Smith Error Code E2: Dry Fire Protection

Severity
Warning
Type
digital display
Estimated repair cost: $150 — $350 (parts + labor)
Warning: Your A.O. Smith water heater has shut down due to a potential dry-fire condition. This means the unit detected overheating, likely due to insufficient water flow. You may be without hot water until the issue is resolved.

How to Fix A.O. Smith Code E2

  1. Step 1: Check that the main water supply valve to the house and the shut-off valves to the water heater are fully open.
  2. Step 2: Inspect the inlet water filter (if equipped) and clean it if it's clogged. The filter is usually located on the cold water inlet line to the unit.
  3. Step 3: Try resetting the water heater by turning it off and then back on. Some models have a reset button. If the error reappears, call a qualified technician.

How to Reset A.O. Smith Code E2

  1. Turn off the unit using the power button on the front panel.
  2. Turn off the gas supply valve.
  3. Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
  4. Restore power at the breaker, then open the gas valve.
  5. Turn the unit back on. If the error returns, the underlying issue needs repair.

What does E2 mean?

The E2 error code on your A.O. Smith tankless water heater indicates a 'Dry Fire Protection' lockout. This safety feature is triggered when the unit senses the burner is firing without adequate water flow to cool it. The heater's control board monitors temperature sensors, and if the temperature rises too rapidly or exceeds a set limit, it assumes a dry-fire condition and shuts down the unit to prevent damage.

This is important because running a tankless water heater without sufficient water flow can cause the heat exchanger to overheat and potentially crack or rupture. A cracked heat exchanger can lead to water leaks and, in some cases, carbon monoxide production if combustion gases are not properly vented. The E2 error is a protective measure to prevent these issues. The unit will remain locked out until the problem is resolved and the error is cleared.

Affected Models

Replacement Parts

PartOEM NumberEst. Cost
Flow Sensor — —
Inlet Water Filter — —
Thermistor — —

Related Codes on Same Models

CodeDescriptionSeverity
E1 Thermistor Failure Warning
E3 Sensor Fault Warning
E4 High Temperature Cutoff Critical
E5 Communication Error Warning
E06 Flammable Vapor Detection Critical
ECO Emergency Cutoff Critical
LOC Controls Locked Warning
UPR Upper Element Fault Warning
LWR Lower Element Fault Warning