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Troubleshooting On Demand Water Heaters

Tankless water heaters heat water directly without the use of a storage tank. When a hot water tap is turned on, cold water travels through a pipe into the unit. Either a gas burner or an electric element heats the water. As a result, tankless water heaters deliver a constant supply of hot water. It is always recommended to hire a professional to do all the important work on your tankless water heater. It is obvious that a customer would rather spend some money to fix their problem once and for all instead of working on it themselves and end up having complications later. Below is a list of few of the troubleshooting tips for tankless water heater so you may have an idea of whats wrong with your system.

No hot water
No hot water is one of the most common tankless water heater problems. The first things you should check are the electric power, water and gas supply to the water heater. Check the shut-off valves, they might be in the closed position.
Check the burner and does the flame rod generate the sparks.
See is there an error code on the unit's control panel, which blocks the heater from running before the previous problem has been solved and system reset.
Is the minimum flow rate achieved? Make sure that the tap is open enough and there are no obstructions in the piping line. Are the unit or water pipes frozen?

Water is too hot
The temperature is set too high. Reduce the temperature to avoid the problem with the scalding.
If water flow is reduced due to the obstructions in the water filter or plumbing, only small amount of water will be heated. Clean the water passageways.
Check are the showerhead or hot water tap clogged and reduce the flow of hot water. Clean the fixtures.
If there is a sediment buildup, you should perform flushing and descaling.
If the temperature sensor is broken, or it is not correctly positioned, try to either re-position it so it is firmly attached to the pipe or replace it with a new one.
Check the output temperature sensor, it might be broken.

Water is not hot enough
Water temperature is set too low. Increase the temperature to approximately 125-130 F.
Reduced the water flow when the water filter or fixture aerator are clogged.
If there is a plumbing crossover, cold water is mixing with the hot water. One of the reasons for the plumbing crossover is if the single-lever mixing valve was installed, and it failed.
Gas valve does not provide enough pressure; either due to the low gas pressure or if it is not open fully. Is the gas line sized correctly?
Sediment and limescale build-up inside the heat exchanger. You might want to use the discaling procedure and flush all the deposits. The scale deposits acts as an insulator and it prevents heat exchanger to transfer heat to water.
Is venting system clean of the debris and does it provide enough fresh air for proper combustion?

Burner does not ignite and no flame is present
See are the electricity, gas and water turned ON and supply a tankless unit with no problems.
Ensure the gas type and pressure are correct and the gas line is properly sized.
Bleed all the air from the gas line.
Check are the flame rod and wiring harness operational, not loose, out of position or damaged.
Does the gas control valve open at all or there is a short circuit?
Is the vent system installed correctly and has a proper length?
Is there an excessive condensation that can distinguish the flame?
Is the flow rate over its recommended minimum? Ensure the flow sensor is working properly.

The unit is too noisy

Check the fan for debris.
Check the burner is it burning the gas with the clear, light blue flame.
Leak in the sealed combustion results in irregular gas combustion.
Unstable burner flames due to the improper venting, lack of combustion air and gas pressure.