War for hot water: Boiler or flow heater? This decides

Understandably, this issue may not be of interest to residents of households connected to district heating and hot water distribution. However, there are less than half of these in the country, and the statistics do not include family houses.

They, as well as small recreational facilities, cottages and cottages, use water from the municipal water supply or from their own well. In order for it to change from lukewarm to hot to boiling, its molecules need to be shaken up. And that’s exactly what happens in a tank heater. After all, the water flowing from the red tap is the basis of the daily running of the household.

To each according to his needs

A classic water heater is usually a double-walled steel enameled tank with protective elements and heating spirals, which usually also have safety fuses and protection against freezing and moisture.

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From the point of view of the source, there are both electric boilers on the market, which can heat water efficiently even in times of lower tariffs (at the so-called night current), and combined boilers, which can operate on both electricity and gas at the same time.

They often send hot water to a smaller circuit connected to radiators. Depending on the size, the heaters are further divided into small flow-through without storage containers and then medium to really large ones with a capacity for hot water of 50-150 liters.

Choose according to the size of your household

The volume of the boiler must correspond to the size and consumption of the household. If you reach for a piece that is too big, your costs will increase disproportionately. If you buy a small one, you will be stuck with a lack of hot water.

A family with one child should expect a minimum daily consumption of 200 liters of heated water, if it grows by another member, it will be 250 liters. It is best to base it on the readings of the water meter or invoicing.

In a place where high consumption is not expected, only a pressureless heater (with a volume of 5-15 liters) will do. It quickly and efficiently prepares enough water at a temperature of 40-65 °C, suitable for washing dishes or hands. In addition, it is possible to install it above or below the sink and wash basin. It is protected by IP25 electrical protection, so it doesn’t mind even higher humidity. However, it has a high demand for immediate power and cannot be considered as a substitute for a boiler.

Heavyweight wins

Most boilers are installed in a vertical position and must be properly anchored to the wall. After all, even without infused water, it weighs several tens of kilograms. Higher-quality heaters tend to be heavier, as they are especially reinforced in places where there is a risk of cutting through during long-term use.

For example, the Mora brand strengthens the usual 1.8 mm thick shell up to 2.25 mm. Enamel is then applied to the rolled sheet at a temperature of 850 °C, which guarantees high resistance even when connected to a water supply line, from which hard mineralized water often flows. And then high-quality polyurethane insulation limiting heat loss is essential. The heating of the water is taken care of by a heating flange with dry tubular bodies housed in a steel casing, which means that they are not at risk of limescale deposits, as is the case in a washing machine, for example.

Additional protection of the boiler is provided by a large magnesium anode, from which no harmful substances are released, in contrast to the anode, where electrochemical processes are manifested by its gradual dissolution.

Therefore, the boiler should be regularly cleaned of deposits and the anode should be replaced once in a while. A new water heater usually lasts at least one decade, after all, better manufacturers provide up to an eight-year warranty on these appliances.

Invisible changes

One of the true proverbs says that you can’t see inside a watermelon… The same can be said about storage containers. What exactly is hidden inside, however, is described by various numbers and technical parameters.

The power of dry tubular bodies is given in kW, and appliances with consumption higher than 5 kW must be connected in three phases and connected to them with a three-pole switch. Another important data is the heating time from 15 to 60 °C, which can easily vary by an hour.

Information on some products in the photo gallery

• In the cylindrical 80l heater Mora Komfort Slim, the temperature is controlled by an electronic thermostat, which prefers an economical setting of 55 °C. You can heat up to twenty degrees higher, but then limescale forms and electricity consumption increases. Mora, Datart
• Heaters of the Mora Excelent series conveniently combine size with volume. Those with a square shape also save space, as they do not protrude into the space as much. They can also be placed lengthwise, but then mixing of water and heating occurs in a larger space, so they consume more and are not as fast. SIKO
• A simple visualization shows a glimpse under the metal shell of the DZ Dražice heater. You can only imagine how high the flanged units with ceramic heating elements and a thermostat in the DHW temperature control range of 5-74 °C reach in the body of the boiler. DZ Dražice
• The Okhe One 20 flat water heater from the DZ Dražice brand has a completely inconspicuous appearance, which can not only be connected to HDO (low price electricity tariff), but also controlled remotely via the HZD application. In addition, it enables really fast heating thanks to the concept of two containers. Heureka
• Vitocell 100-B steel bivalent storage tank for water heating with Ceraprotect surface treatment and highly effective all-round thermal insulation that ensures low heat loss. Thanks to the large indirect spirals, the water is heated quickly and evenly. There are storage tanks with a volume of 300, 400, 500, 750 or 950 liters to choose from. Viessmann
• Small electric pressure water heaters Stiebel Eltron SHC are intended for the preparation of hot water wherever frequent withdrawals in a smaller volume are required. The volume of the reservoirs is 10 or 15 liters and they are installed under the sink. They can be used for one or more hot water intake points in combination with conventional pressure batteries. Stiebel Eltron
• Velis Wifi flat electric water heater in energy class B, which is not only space-saving (only 27.5 cm deep), but also powerful enough for a family. The construction of two interconnected reservoirs provides users with comfortable heating of the TV with a smaller volume of heated water, and thus with lower operating costs. Wifi gateway for connecting to home wifi will enable control from anywhere using the app. Ariston
• Wall-mounted storage water heaters Stiebel Eltron PSH Trend are suitable for supplying multiple take-off points. They are intended for vertical installation on the wall. They achieve very low heat losses thanks to the extremely strong thermal insulation of 48 mm. The inner tank of the heaters is equipped with a special high-quality CoPro enamel. Stiebel Eltron
• Lydos Hybrid Wifi is the first hybrid electric water heater in energy class A, which combines classic resistance water heating and heat pump water heating. Combined with a number of smart functions integrated into the control system, you can achieve up to 50% savings on water heating costs compared to an older heater. An interesting feature is the possibility to hide unsightly hot and cold water pipes in the body of the heater. Ariston
• Electric water heaters from the DZ Dražice cooperative called simply TO (thermal heater) can be placed under (so-called in) or above (so-called up) the collection point. Depending on the size, they also differ in the heating element with an input power of 1.5 kW or 2 kW. A whole series of these modules won the prestigious Big See Product Design Awards. DZ Dražice

Energy classes will tell

And then there is the scale of energy classes. Water heating is the second most financially demanding household activity, so it undoubtedly deserves more attention. Most heaters still fall into category C, but you can already find energy-saving modules classified in class B as well as devices with the eco smart function for economical operation and diagnostics.

“The regime is suitable for those who have established habits related to water consumption. For example, they shower at the same time every weekday. You record these requirements in the electronic module, thereby reducing your electricity bill.” explains Ján Takáč from Mora. You can save up to 15% of costs this way.

As already mentioned at the beginning, heaters are connected to the network every day, so in the long term, lower consumption and smart use (similar to refrigerators, for example) must show.

You could find this article in Dům&Zahrada magazine No. 2/2024.
Source: House&Garden

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