Tankless Water Heater Problems

Common problems with tankless hot water heaters and how to troubleshoot

Common Problems with Tankless Water Heaters

Tankless problem #1: No ignition

Tankless problem #2: Flame failure

Tankless problem #3: Overheating and thermal fuse failure

Tankless problem #4: Temperature fluctuates

Tankless problem #5: Water is not hot enough

Tankless problem #6: Water is too hot

Other problems

Troubleshooting no ignition problem. Burner does not ignite when the hot water tap is open

• Proper gas pressure coming to your tankless heater has to be provided.

• To avoid problems with the heater, ensure that the unit is properly grounded.

• Verify the fuses in the control unit are OK.

• Ensure wiring harness and igniter are operating properly and that the electrode can produce a spark.

• Check the electrical short on components.

• Check gas valve, does it open.

• Check inside the combustion chamber that burners are properly installed and seated.

• Check that there is no condensation or any kind of debris on the burner that can lead to the gas burning problem.

• Check is the flow sensor works correctly.

• The flow switch doesn't open as the minimum pressure in the incoming supply is not met. If the flow is too low, the burner will not ignite. Low pressure is one of the most frequent tankless water heater problems easy to fix.

• An inlet filter is dirty and clogged.

• Check for the correct hot and cold water installation (make sure that lines are not installed in reverse order).

• You might experience sediment build up in the faucet aerators or shower head which causes the problem where the tankless unit doesn't activate.

• Crossover in plumbing due to failed washer at a single lever faucet, incorrect plumbing or faulty mixing valve.

Troubleshooting flame failure problem

• Check is the proper venting installed.

• Is the heater condensation collar correctly installed?

• Vent length should be within limits specified by the manufacturer.

• Check for the loose electrical connections on the electrode.

• Ensure that the proper voltage is within limits.

• Check components for electrical short.

• Gas valve works properly?

• Is flame rod wire connected?

• Deposits on the flame rod? Carbon build-up can be cleaned with the sand paper.

• Presence of condensation and debris on the burner?

How to solve the problem with the overheating, thermal fuse failure or heat exchanger sensor fault

• Is the wrong gas type used?

• Air flow around the heater and its vent terminal is blocked.

• There is a low flow inside the heat exchanger.

• The presence of the foreign materials inside the combustion chamber and venting.

• Cracks on the heat exchanger.

• Scale build up inside the heat exchanger creates an uneven temperature distribution and hot spots.

• Clogged heat exchanger.

• Dirty sensor.

How to solve problem when hot water temperature fluctuates

• Ensure that there are no restrictions in the flow (dirty or clogged shower heads, faucet aerators).

• Clean the filter if it is dirty.

• Check for plumbing crossover.

• Check for the water pressure that it doesn't fluctuate.

Troubleshooting when outgoing water is not hot enough

• Temperature selection is too low. Increase the temperature either on the unit or on the remote control.

• If the water runs cold, increase the flow so the minimum required pressure is met. Keep in mind that you will not get the hot water immediately, it takes time for hot water to reach the tap. The longer the distance between tankless water heater and your fixture the longer it gets for hot water.

• Tankless water heater doesn't produce enough heating power. An adequate gas pressure and gas line has to be provided for different models and manufacturers.

• Ensure that temperatures sensors are making contact and are firmly mounted on the pipes.

• Crossover in plumbing - cold water is mixing with the hot water and therefore decreasing the outlet water temperature.

Troubleshooting when outgoing water is too hot

• Selected temperature on your tankless water heater is too high. Select the lower temperature.

• Inlet filter is dirty... clean it.

• Make sure that there are no water path obstructions, including faucet aerators, shower heads...

• Is the heater using the specified gas type?

• Temperature sensors are loose... ensure that sensors are firmly mounted and are making contacts.

Other problems that you might experience

Prevent Tankless Water Heater Problems

• Clean the burner, control compartments and circulating air passageways.

• Inspect the venting system.

• Do the visual inspection of the flame to ensure that it burns with a clean, blue and stable flame and evenly on the entire surface of the burner.

• Keep fan and motor free of dust and dirt.

• Flush the heat exchanger with a descaling solution if mineral build up is evident.

• Keep the area around the vent exhaust free of snow and ice.

• Overheating - the unit will automatically shut down when the appliance exceeds a predetermined temperature.

• Flame failure - the water heater will shut down if the flame is gone.

• Power failure - if the appliance loses the power the safety feature will cut the gas off.

• The fuse will blow when overcurrent occurs.

• Fusible link will break if the extreme temperature occurs.