The Thermo Top series has been around for a while and is a loyal servant who is still alive. The heater series comes in four variants and what separates the heaters are the following:
Thermo Top Z is an auxiliary heater that does not have a water pump. It is often mounted on diesel vehicles to help the engine reach operating temperature when it is cold outside.
Thermo Top E is a complete parking heater of 4.2kW. It is about the same size as the other models but gives a little less power.
Thermo Top C delivers 5.2kW and is the equivalent (predecessor) to EVO 5. It is well suited for normal sized passenger cars.
Thermo Top P also delivers the 5.2kW but has a different control unit compared to the others. Among other things, it pulsates the water pump, which causes the water to heat up faster.
You can find the exploded sketch by clicking on this link. It downloads a clickable pdf with all components to the heater. In order to read the downloaded file, a pdf reader is required.