This is one of the most common "problems" that is often easy to fix. We'll first explain the construction of the heater and how the various components work together.
The heater has a flow guard (FS) that moves from the water flow provided by the circulation pump. The flow through the heater needs to be at least 3600 l/h for the flow switch to activate the microswitch (MS). It then supplies current to the heating element until the set water temperature has been reached. During the time that it is heating, the indicator light (ML) also lights up.
If the water flow is insufficient, there will not be enough water flow to move the paddle enough to activate the microswitch (MS). If there is too little water, the pump starts to suck in air and then the overheating protection (T2) can trip. The cause can also be a dirty filter.
If any of the above occurs, the circuit is broken and the heating element cannot function.
Watch the video carefully and it will be easier to understand the text. Also feel free to pause the video to be able to read the text and look at the picture at the same time.
Faults that may occur to cause the heater not working:
>> Figuring out the reason why the heating does not work can also be done by measuring the current circuit.
Digital thermostat settings and thermostat errors can also cause the heater to not function.
According to the instructions, the knob on the mechanical thermostat must always be set to the maximum position if a digital thermostat is used. The function can be checked by turning the thermostat knob between minimum and maximum. If a faint click is then heard, the thermostat is OK. If no click is heard, the thermostat may be out of order and needs to be replaced. BUT, if there is also a digital thermostat, the heater's own thermostat is not needed and it can be bypassed.
Here are also various instructions that come with the products: