321 🟡 Repair Required

Takagi Error Code 321: Inlet Temp Sensor

⚠️ Your Takagi tankless water heater has detected a problem with its inlet water temperature sensor and has shut down to prevent potential damage. You will have no hot water until this is resolved.

How to Fix Takagi Code 321

  1. Step 1: Check the water heater's display for any other error codes. Note them down, as they may provide additional clues.
  2. Step 2: Reset the water heater by turning off the power at the breaker for 30 seconds, then turning it back on. This may clear a temporary error.
  3. Step 3: If the error persists after resetting, contact a qualified HVAC technician to diagnose and repair the issue.
Type: digital display

What Does Takagi Error Code 321 Mean?

The Takagi error code 321 indicates that the water heater's control board is receiving an unexpected signal from the inlet water temperature sensor. This sensor is responsible for measuring the temperature of the incoming cold water supply. The control board uses this information to properly modulate the burner and maintain a consistent output temperature. If the sensor is faulty, or the wiring is damaged, the control board won't know the incoming water temperature, and the unit will lock out for safety. This prevents the unit from overheating or operating inefficiently. It's important to address this issue promptly to restore hot water service and prevent potential damage to the unit.

Common Causes of Takagi Code 321

  • Faulty inlet water temperature sensor
  • Loose or corroded wiring connections to the sensor or control board
  • Damaged wiring harness leading to the sensor
  • Sediment or scale buildup on the sensor, affecting its accuracy
  • Control board failure

Applicable Takagi Models

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Replacement Parts for Takagi HVAC System Code 321

Inlet Water Temperature Sensor OEM: TK10014
Control Board