with flow-through DHW heating

Gas boilers Junkers, Protherm, Vaillant and others with flow-through heating (plate heat exchanger)

Condensing boilers with flow-through heating are used for heating radiators or underfloor heating, and at the same time heat domestic hot water directly in the boiler via a small flow-through heat exchanger built directly into the boiler's construction.  The boiler primarily heats the heating circuit, and when a water tap is opened, water starts flowing through the boiler, the three-way valve automatically switches, and the boiler starts heating this water at full output. The boiler can draw combustion air from the room or directly through the wall from outside.  Flue gas exhaust must be carried out using a plastic flue pipe that is sealed against condensate. 

The boiler can be controlled using a classic room thermostat, or an equithermal (weather-compensating) controller.

Frequently Asked Questions

• What is the difference between flow-through heating and a storage tank? With flow-through heating, water is heated instantly on demand directly in the boiler, without a storage tank – the boiler is therefore more compact, but the hot water output is limited by the boiler's instantaneous power.
• Is flow-through heating sufficient for multiple bathrooms at the same time? With simultaneous draw-off at several points (e.g. two bathrooms at once), the boiler's output may not be sufficient – in that case a boiler with a storage tank, or a set including a storage tank, is more suitable.
• Is flow-through heating more economical than a storage tank? Yes, since only the water that is actually drawn is heated, without the heat losses of a storage tank while it is kept hot.
• What boiler output is suitable for flow-through domestic hot water heating? For a typical household with one bathroom, an output of around 24 kW is sufficient; for higher hot water flow demands, a higher output is recommended.