Construction of the heat exchanger in a water heater

Construction of the heat exchanger in a water heater

Water heating systems are based on various types of heat exchangers. Their advanced design allows for efficient transfer of heat from a heating device (e.g. boiler, heat pump or infrastructure of the municipal heat distribution network) to the boiler water circulating in the system, and then from the circuit to the rooms. There are many types of heat exchangers, from large industrial shell and tube constructions, to widely used plate-type heat exchangers (municipal networks, air conditioning, ventilation with heat recovery), through to finned coil heat exchangers, which can be found, among others, in heat pumps and water heaters. 

What does the heat exchanger in a water heater consist of? 

The heat exchanger in a heater should be constructed in such a way as to ensure the largest possible contact area between the air pumped by the fan and the pipes in which the boiler water flows. It is for this reason that finned coil heat exchangers are used in them. They consist of a densely arranged copper coil pipe, which already creates quite a large heat exchange surface. To further enlarge it, fins are mounted on it – properly formed, thin, densely arranged aluminium plates. In the sonnEC water heaters, the 1-, 2- and 3-row heat exchangers are installed. Each additional row of pipes increases the heating power of the device and allows the connection of low-temperature heat sources.

In order to optimise the heat exchange even better, the heat exchangers are connected in a counter-flow arrangement. This means that the direction of the flow of the circulating water is opposite to the air flow. Thanks to this, it is possible to keep the smallest possible temperature difference between them, which is reflected in the efficiency of the whole process. 

Why copper and aluminium?

The factor that largely determines the efficiency of the heat transfer process from the boiler water to the air is the thermal conductivity of the metal of which the heat exchanger is made. The higher it is, the better. For this reason, copper is often used for the production of coil pipes, due to its high resistance to corrosion and durability. The production of the entire finned coil heat exchanger of copper is quite expensive, and the resulting device is heavy. Therefore, the fins are often made of aluminium – a cheaper and lighter material that simultaneously provides satisfactory thermal conductivity. 

Safety of use

Each heat exchanger installed in the sonnEC devices undergoes leak tests. Therefore, the risk of any leakage is negligible. The most common source of leakage is usually connection elements, which during installation of the heater were incorrectly screwed and sealed, not the exchanger itself.

The tight arrangement of fins and coils favours the accumulation of dirt around them. If you want to remove it, you should be careful – thin elements are quite delicate and the use of excessive force may cause their deformation, which will negatively affect the efficiency of the heat exchange process. 

High quality and affordability 

Modern heat exchangers used in water heaters allow for effective and cost-efficient heating of rooms. The advanced design gives the possibility of reducing the heating water parameters, thanks to which it is possible to use more environmentally friendly, low-temperature energy sources.


Tags: