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How to fix Navien tankless hot water system when it has no error code?

Alton Alexander
By Alton AlexanderUpdated on June 4th, 2022

If your Navien tankless water heater is showing the error code "no hot water," it means that the unit is not heating the water to the set temperature. There are a few potential causes for this error code:

  1. The water heater's inlet water temperature may be set too low. Try turning up the water heater's inlet water temperature knob to see if that fixes the problem.

  2. The water heater's gas valve may be turned off. Check to make sure that the gas valve is in the "on" position.

  3. The water heater's flame sensor may be dirty. Cleaning the flame sensor may fix the problem.

  4. The water heater's control board may be faulty. If the control board is faulty, it will need to be replaced.

If your Navien tankless water heater is showing the error code "no hot water," it is likely due to one of the above issues. Try troubleshooting the problem by checking the water heater's inlet water temperature, gas valve, and flame sensor. If the problem persists, the control board may need to be replaced.

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1. Check the thermostat settings

  1. Open the front cover of the thermostat.
  2. Look for a temperature setting that reads "Fan Only."
  3. Change the temperature setting to "Heating."
  4. Check the "On Demand" setting to make sure it is set to "Auto."
  5. Look for a "No Heat" or "No Hot Water" error code. If the error code is present, take the following steps to correct it: -Check the water pressure. -Check the fuses. -Check the wiring.

2. Check the pressure relief valve

  1. Turn off the water supply to the house
  2. Remove the water meter from the water line
  3. Remove the water line from the valve box
  4. Remove the pressure relief valve
  5. Clean the valve and mounting surfaces
  6. Reinstall the pressure relief valve

3. Check the inlet water supply valve

The steps to check the inlet water supply valve in order to fix navien no hot water no error code are as follows:

  1. Open the front cover of your refrigerator.
  2. Look for the inlet water supply valve on the left side of the fridge.
  3. Turn the valve to the off position (clockwise).
  4. Wait 10 minutes.
  5. Turn the valve back to the on position (counterclockwise).
  6. Wait another 10 minutes.
  7. If the water has not been restored, the inlet water supply valve may be defective and needs to be replaced.

4. Check the gas supply

  1. Turn off the gas to the range and all other appliances in the area.
  2. Check the gas supply to the range by using a gas detector. If there is no gas, then the range may need a new gas line.
  3. If there is gas, then check the gas supply to the range by using a gas meter. If there is no gas, then the range may need a new gas line.
  4. If there is gas, then check the gas supply to the range by using a carbon monoxide detector. If there is no gas, then the range may need a new gas line.
  5. If there is gas, then check the gas supply to the range by using a hot water tap. If there is no hot water, then the range may need a new water line.
  6. If there is gas, then check the gas supply to the range by using a thermostat. If there is no gas, then the range may need a new thermostat.

Some users might also have success with the following opitons:

  1. Check the power supply to the unit.
  2. Check the igniter.
  3. Check the burner assembly.
  4. Check the heat exchanger.
  5. Clean the heat exchanger.
  6. Replace the heat exchanger.