Boiler: Instantaneous water heater & hot water tank

If you do not have a central hot water supply, you must connect a decentralised hot water boiler to each individual tap in the bathroom and kitchen. Under-table appliances, open small cylinders and electronic instantaneous water heaters are available.

Instructions: Connecting a hot water boiler

If the water for washing, showering, bathing or rinsing is not centrally heated by the boiler in the cellar, the alternative is: electricity. Since the energy from the socket is considered the most expensive variant due to the efficiency losses during generation, efficient, energy-saving heating is all the more important here. The decentralised heating of water always takes place in the immediate vicinity of the standpipes. This avoids the heat losses that would otherwise have to be accepted when distributing water from a central heating system to remote tapping points. In addition, water at the desired temperature is available immediately after the tap is turned on, so that no drinking water is lost.

In order to make decentralised water heating as demand-oriented and efficient as possible, our table gives you advice on the most common device types for all typical applications. Open small accumulators have proven their worth on kitchen sinks or individual washbasins. They are called ‘open’ because the water vapour generated during heating escapes dripping through an outlet. This is why open under-table units are always installed in conjunction with a low-pressure fitting.

Under-table unit for 230 V connection

A single washbasin – in the converted attic – you can also supply a small instantaneous water heater with hot water. All you need here is a normal 230-volt socket near the washbasin (be careful: it must be splash-proof!). The units from 3.5 to 6.5 kilowatts are small and inconspicuous and fit even in narrow niches under small hand basins. And unlike a small storage tank, water is only heated when it is needed. This reduces energy consumption by up to 65 percent.

Electronic instantaneous water heater: Setting the temperature
If you are sometimes in the shower and cannot regulate the water temperature as desired despite a single-lever mixer, this is annoying in many respects. On the one hand you don’t get to shower, on the other hand the water flows unused into the drain. This is often the fault of the instantaneous water heater. This type of water heating can be controlled in two different ways: hydraulically or electronically. With hydraulic instantaneous water heaters, the control of the water temperature depends on the flow rate. If this decreases, i.e. if too much cold water is added or the overall flow rate is reduced, the relay does not switch on and the water is no longer heated at all. Electronic instantaneous water heaters regulate the water temperature independently of the water pressure or flow rate. This means that even if only one trickle flows through the pipe and runs out of the fitting, the water is still heated to the temperature set on the appliance. Unwanted changing showers are then a thing of the past, and you also save energy and money.

Electronic instantaneous water heaters, however, require a little adjustment: in order to work really economically, the water temperature should be set on the device exactly as it is actually needed. So if you prefer to shower with 38 degrees Celsius warm water, this temperature should be entered on the appliance and the single-lever mixer should be set all the way to the left (no mixing of cold water!). If you want the water to be warmer or colder, press the plus or minus switch on the appliance and set the new temperature in the twinkling of an eye. With our instantaneous water heater, two temperatures can also be programmed. Just press one of the program buttons for about five seconds and the temperature is stored.

Replacing the hydraulic instantaneous water heater

Attention: An exchange may become problematic if the devices have a different performance. If, for example, you have a 13 kW device that is fused with 20 amps, you cannot simply connect a 24 kW heater, because it must be fused with 35 amps. If it is not, the fuses will fly out regularly at full power. Since you are not allowed to make any changes to the fuse box, you must consult an electrician. The same applies to the existing conductor cross-section: for 13 kW devices the required cross-section is 2.5 mm2 , for 24 kW devices it should be 6 mm2 . If the conductor cross-section is underdimensioned, but the fuse is correct, the fuses do not switch off in the event of overload and a cable fire occurs. It is therefore very important to select a continuous-flow heater that matches both the existing fuses and the conductor cross-sections or to have the necessary changes made by an electrician. For a shower and a washbasin 21 kW devices are sufficient. However, the more taps you supply, the stronger the appliance should be, because stronger appliances can supply more hot water per minute. It may therefore be advisable to connect a 24 kW unit.

When buying, you should therefore know how many taps you want to supply so that you can be recommended a suitable appliance. Follow water tech’s pinterest to discover more water tank pins and boards related updates.


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