Takagi Error Code 720: Remote Control Error

Severity
Warning
Type
digital display
Estimated repair cost: $100 — $350 (parts + labor)
Warning: Your Takagi tankless water heater has detected a communication problem with the remote control and has locked out. You will not have hot water until this is resolved.

How to Fix Takagi Code 720

  1. Step 1: Check the remote control's batteries (if applicable) and replace them if needed.
  2. Step 2: Inspect the wiring connections at the remote control and the main unit (if easily accessible without removing any panels) for any obvious signs of damage or loose connections. Gently try pushing the wires into their terminals.
  3. Step 3: If the problem persists, contact a qualified HVAC technician to diagnose and repair the issue.

How to Reset Takagi Code 720

  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.

Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.

What Does Takagi Error Code 720 Mean?

The Takagi error code 720 indicates a problem with the communication between the main control board in your tankless water heater and any connected remote controls (if you have one installed). The remote control allows you to adjust the water temperature from a different location, like a bathroom. This error means the main unit isn't 'hearing' from the remote, or vice versa. The unit will shut down to prevent unexpected temperature changes or operation without proper control. This error can stem from a simple wiring issue, a faulty remote control, or a more serious problem with the main control board in the tankless unit itself. Because the unit locks out, you won't have hot water until the issue is resolved. Troubleshooting requires some electrical testing, so if you aren't comfortable with that, it's best to call a qualified technician.

Common Causes

  • Loose or corroded wiring connections between the remote control and the main unit.
  • Faulty remote control unit.
  • Damaged or improperly shielded remote control wiring.
  • Defective main control board in the tankless water heater.

Diagnostic Steps

If... Check Expected
Remote control is installed and wired to the main unit Measure the voltage at the remote control terminals on the main control board. Typically 5-12 VDC. Refer to the Takagi service manual for your specific model.
Voltage is present at the remote terminals Check the continuity of the wiring between the remote control and the main unit. Low resistance (near 0 ohms) on each wire.
Wiring is intact Substitute a known good remote control (if available) to see if the error clears. Error 720 disappears, and the remote functions normally.

Applicable Takagi Models

Replacement Parts

Part OEM Number Est. Cost Where to Buy
Remote Control — — —
Main Control Board — — —

Related Codes on Same Models

Other codes that affect the same Takagi model families as 720.

Code Description Severity
101 Combustion Abnormality Critical
111 Ignition Failure Critical
121 Flame Failure Critical
200 Overheating Warning
207 Bypass Valve Error Warning
291 Flow Rate Issue Warning
312 Outlet Temp Sensor Warning
321 Inlet Temp Sensor Warning
391 Exhaust Temp Sensor Warning
510 Gas Solenoid Valve Critical