For the organization of autonomous hot water supply (DHW) of apartments and private houses, 2 groups of heaters are used - boilers and columns. The former gradually accumulate heat in a tank of 30 ... 500 liters, the latter warm water “on the go”, immediately after opening the tap. We propose to consider the pros and cons of each type of household appliances and find out which water heater is better - flow or storage.
On the types and principle of operation of different heaters
Before embarking on a comparison, we briefly list the varieties and design features of domestic water heaters. The first group - boilers - these are insulated tanks with a capacity of 30 to 500 liters, heated by low-power heat sources:
- electric heating elements consuming 1.5 ... 3 kW;
- gas burner with a thermal power of 3 ... 5 kW;
- a spiral coil heat exchanger connected to the heating system (more precisely, to the boiler).
Accordingly, all storage water heaters are divided into 3 types - electric, gas and indirect heating. Storage tanks with a volume of up to 200 l are offered in wall and floor versions, over 200 liters - in floor.
Note. There are also combined water heaters, for example, indirect heating tanks with electric heating elements.
The principle of operation of the boiler is simple: a heater, a burner or a coil heats the entire volume of water in the tank until the temperature set by the user is reached. Then the heat source is turned off and started only to maintain this temperature. The heating of the tank lasts 1 ... 3 hours, depending on the amount of water and the type of heating element (the burner copes faster than the heater).
Flowing water heaters differ from boilers in power - it is much higher. After all, the device must have time to instantly warm up the water as soon as the user opens the faucet in the bathroom or in the kitchen. The heat source is the same heating elements and high-performance gas burner devices. The heater is turned on automatically - by the signal of the flow sensor.
In private houses and apartments, 3 types of instantaneous water heaters are installed:
- geysers;
- electric speakers for showers;
- electric heaters in the form of kitchen taps.
The thermal power of natural gas-fired speakers starts at 8 kW, and the electric power starts at 3 kW (kitchen taps). Flowing shower heaters consume more - from 8 kW. All household appliances of this type are designed for wall mounting.
Comparison of water heaters
To choose the right flow or storage water heater for your own apartment or country house, we offer to compare these devices according to 4 important criteria:
- The complexity of installation and connection.
- Convenience of use.
- Profitability.
- Service.
Reference. Comparing water heaters at a cost does not make much sense, the price range is quite large. If you take a boiler and a column of approximately the same class and performance, the first will cost 20–40% more.
The reliability of the devices is highly dependent on the operating conditions and the manufacturer. Example: theoretically, the European Gorenje drive is much more reliable than the Chinese Novatek, but with significant voltage drops in the network it will fail just as quickly. Similarly with the columns: due to poor water quality, problems with the details of the water unit - the membrane and the valve - will soon arise.
Installation complexity
From the installation point of view, the pros and cons of instantaneous water heaters look like this:
- Due to its small size and weight, the device is easily placed in any (permitted by the norms) premises. The mounting method is wall mounted.
- The connection scheme to the cold water supply and hot water supply is simple - we connect the pipes through the shut-off valves, we put a dirt filter.
- Minus the electric speaker - you need decent power at the entrance to the house, a separate power line, a protective ground loop.
- A significant drawback of the gas flowing "water heater" is the difficulty of connecting to the natural gas pipeline. It will require the permission of the supplier, the project, qualified installation and official commissioning.
Addition. To divert the combustion products of the geyser, you need a separate chimney channel plus supply and exhaust ventilation, at least a kitchen window. It is prohibited to use the existing ventilation duct as a chimney.
Preliminary conclusion. If there is no chimney in the apartment or there is not enough allocated electric power, it will not be possible to install a flow-through hot-water apparatus. In this case, only a 3 kW electric faucet is available.
Now consider the advantages and disadvantages of storage boilers:
- For the operation of the tank with electric heating, 3 ... 5 kW of power allocated to the apartment will suffice.
- Installation of an electric heater or indirect heating tank is done without the permission of third parties. The gas boiler is connected to the fuel line by analogy with a column, therefore, it is fraught with bureaucratic difficulties.
- Accumulative capacity is more difficult to place in the house due to the large size and weight.
- A gas or electric heater is connected to the water supply network in the simplest way - shut-off valves, a filter and a safety valve (usually included) are installed.
- Indirect heating boiler requires more complex strapping. An example of connection is shown below in the diagram.
- For the installation of a tank equipped with a gas burner, it is necessary to arrange a chimney and normal air exchange.
So, the boiler is allowed to be installed wherever there is enough space or there is the possibility to securely attach the tank to the wall. Large electrical power is not required. The exception is the gas apparatus, serious requirements are imposed on it. An indirect water heater is more difficult to connect, in addition to shut-off valves, a circulation pump and an expansion tank will be needed.
Ease of use
The difference between the storage and instantaneous water heaters is the method of heating - the first brings a large volume of water to a predetermined temperature, the second heats the flow "on the go", using high power. From here the following restrictions arise:
- The column raises the temperature of the water by a certain delta, as far as the performance of the heater allows. Example: an electric device with a capacity of 10 kW is able to provide a shower head (flow rate 5.5 l / min) at an initial water temperature of +15 ° C. Details of the characteristics of water heaters under different conditions are indicated in the table.
- If the flow rate in the DHW network increases, the outlet flow temperature will decrease. Imagine you are washing in the shower, and someone from the household opened the faucet of the kitchen faucet and you get a portion of cold water. You need to buy a column with a decent margin of power or open the valves one at a time.
- A heated boiler is capable of immediately delivering a large amount of hot water to several consumers. Only the volume of this water is limited, and it will take 2 ... 3 hours to heat the next portion.
So, the storage tank is limited by the amount of water, and the flow tank is limited by temperature. To make the use of the device as convenient as possible, it is necessary to increase the capacity of the boiler or the power of the column. An alternative solution is scheduled cleaning, saving hot water to the detriment of comfort.
Which water heater is more economical
As already mentioned above, flow heaters are more powerful than storage heaters. Nevertheless, in terms of energy consumption, columns are more profitable than boilers for 3 reasons:
- regardless of the insulation layer, the heated storage tank constantly loses heat, which is why the automation periodically turns on the heater or starts the burner to maintain the temperature;
- the boiler begins to warm long before the moment of consumption of hot water, spending electricity or gas;
- the column includes heating only during tapping, there are no heat losses.
Note. If, when comparing, the efficiency of gas water heating plants is taken into account, then a turbo column with a closed combustion chamber will receive an additional advantage over the boiler, since it burns fuel more efficiently.
It is hardly possible to evaluate profitability in practice. You will have to supply 2 different water heaters of comparable performance and use alternately for 1–2 months. None of the homeowners will do this.
Need for service
According to this criterion, storage capacities lose to flow-through devices. Often, you do not have to service the water heater, but prophylaxis needs to be done once in 1-2 years. What does it consist of:
- flushing the tank and cleaning the heater from scale (except for ceramic "dry" type electric heaters);
- Once every 2–4 years, the protective magnesium anode is replaced;
- weekly, the boiler warms up to the maximum in order to destroy pathogenic bacteria, in particular Legionella.
Scales also form in heat exchangers and heating elements of the columns, but the process is much slower due to running water. Preventive cleaning / flushing of heaters is best done at least 1 time in 3 years, and with hard water - annually.
Which water heater to choose - recommendations
When we studied the features of various household appliances, it becomes clear that the choice of a heater for domestic hot water depends on the conditions of installation and operation. Here are some tips:
- In an apartment where power supply is limited and a chimney is not built, you can only buy a storage electric water heater of 1.5 ... 2 kW. Another solution is a turbocharged column, provided that it is possible to coordinate the output of the coaxial pipe through the wall.
- In a gasified private house, it is better to install a flowing gas heater, this is the most profitable option.
- In the absence of main gas, but in the presence of permitted power at the input of 10 kW, definitely choose an electric column. It takes up little space and helps save on electricity compared to a boiler.
- In other cases, a boiler should be installed. To select the volume of the water heater, study the table below, which indicates the capacity of the storage tank, depending on the number of family members and the mode of operation.
- An indirect boiler is very appropriate if there is a solid fuel boiler or a furnace with a water circuit in a country house. It will help to remove the excess heat generated by wood heaters.
Comment. An indirect heater works just as successfully with gas, diesel and any other boilers.
The most common issue is the use of a gas storage water heater. It is not very clear why to purchase and install a large tank, if it is cheaper and easier to buy a gas column. The registration procedure is exactly the same. Judging by the reviews on the forums, such devices are not too popular among homeowners.
Conclusion
Let's try to give an unambiguous answer to the question of which water heater should be chosen - flow or storage. When there is a technical possibility, we recommend always placing the column - gas or electric. The main thing is to choose the right power. Boilers are more expensive, larger and consume more energy.But there are exceptions, for example, heating the drive at night at a cheap rate for electricity with the further use of hot water during the day.