Due to stereotypes, the name “boiler” is often associated with an electric hot water tank. Although there are other versions of household appliances that provide autonomous hot water supply to private homes and apartments. Under certain conditions, the use of gas appliances and indirect heating tanks is much more profitable and comfortable. To choose a storage water heater, it is worth comparing the principle of operation of different types of boilers, the nuances of connection and operation features.
What is important to know about the electric boiler
The design of the water heater shown in the diagram below includes the following elements:
- an external metal case of cylindrical or rectangular shape, equipped with a wall mount bracket;
- enamelled or stainless steel inner tank;
- a heater - a heater with a power of 1.5-2.5 kW, installed vertically in the lower zone of the tank;
- magnesium or titanium anode;
- thermostat - remote or mounted in a heater;
- cold and hot water supply tubes;
- thermometer;
- an obligatory element of the piping - a two-in-one non-return safety valve usually comes with a heater;
- controls are located on the lower end of the cylindrical tank or on the front panel of the rectangular version.
Note. The space between the outer casing and the inner water tank is filled with polymer insulation. In cheaper models, conventional tubular electric heaters are used, in more expensive ones, “dry” type heaters with ceramic anti-scale protection are used.
How does an electrically heated boiler work:
- After installation and connection (the diagram is shown in the next section of the article), the internal volume of the tank is filled with cold water through a tube that goes to the bottom of the tank.
- Next is the inclusion and heating of the mass of water by the heating element. When the temperature reaches the set or maximum value, the thermostat turns off the electric heater.
- Water is drawn through a pipe ending in the upper zone of the tank, where the water temperature reaches its highest point. At the same time, the tank is recharged from the water supply through the lower tube.
- During the operation of the DHW system, the water in the tank is cooled, the thermostat automatically turns on the heating element. If there is no water intake, the contents of the tank are periodically heated by a heating element in order to maintain the desired temperature.
Reference. The maximum heating temperature of most boilers is 75 degrees; the recommended temperature for saving electricity is 55 ° C. Some models are equipped with an overheating sensor that turns off the heater when the threshold is +85 ° C.
Wiring diagram
Installing and connecting an electric water heater to the pipes is not difficult and, if desired, is performed independently:
- Fix the tank on the wall using standard brackets. The room for the location of the boiler is a kitchen, bathroom or boiler room.
- Connect the device to the water supply and DHW networks, guided by the scheme.
- Power is supplied from a conventional outlet equipped with a grounding contact.
Let us explain the functions of some parts of the harness. The key element is a 2-in-1 valve installed at the boiler inlet and solving 3 tasks:
- do not allow the container to empty back into the water pipe;
- relieve excess pressure resulting from heating and expansion of the fluid inside the closed tank;
- forced discharge of water.
The remaining shutoff valves are needed for the convenience of repairing and cleaning the water heater.To remove the unusable magnesium anode, the container must be emptied. The discharge through the spout of the standard valve takes too long due to the small bore, it is better to put a tee and an additional tap.
Comment. The quick drain scheme is especially relevant in country houses with periodic heating. In order to protect the water supply from defrosting in winter, the owners have to empty the system each time before leaving.
Americans and shut-off valves are useful in the event of a breakdown, when the heater needs to be removed and repaired without disassembling the water lines. Why a sane homeowner knows why a filter is needed at the entrance to a building.
Advantages and disadvantages
Enumerating the advantages of boilers, we will not mention the features inherent in all storage heaters. Pluses of electric devices:
- reasonable price of a water heater;
- ease of installation and strapping;
- permission to connect to the mains is not required;
- relatively small sizes;
- execution of units - vertical or horizontal, wall or floor;
- maintenance - not more than 1 time in 2-3 years, performed independently.
Reference. The cost of a DHW cylinder with a 100 liter tank starts at 120 oz. e. (Ariston model SB R 100 V). Chinese counterparts will cost even cheaper.
Maintenance of the boiler includes flushing, cleaning, replacing the magnesium anode. If the moment of critical wear of the anode is missed, electrochemical corrosion will take on the copper of the heating element and the metal of the tank. The rusted capacity is not restored - you need to buy a new device. The same with the burned heater.
Now about the cons of electrical appliances:
- according to the heating rate (about 2 hours), the products lose to gas and indirect devices of the same volume;
- consumption of expensive energy;
- the inability to check the condition of the anode without disassembling the unit;
- limited capacity.
Electric heaters are sensitive to water hardness. The higher the content of magnesium and calcium salts, the sooner the anode "melts" and the thicker the scale layer on the walls and the heater body. The issue is resolved by annual cleaning.
Gas storage water heaters
Externally, the unit resembles a vertical version of an electric drive - a cylindrical body, pipe fittings and a thermometer on the front side. Only on top appeared the chimney pipe, and below - an additional section with gas equipment.
The internal structure of a boiler using natural or liquefied gas has significant differences:
- in the lower additional section is an open (atmospheric) combustion chamber and gas burner;
- a vertical fire tube penetrates the tank, leading the combustion products out through the external pipe with a cap;
- a draft sensor and a turbulator are placed inside the chimney, causing the hot gases to move more slowly and actively exchange heat with the water tank;
- a condensate collection tank is located below the burner;
- fuel supply is controlled by safety automatics - non-volatile gas valve of SIT Group or another manufacturer;
- The tank has an immersion sleeve for a thermostat sensor connected by a capillary tube to a safety valve.
Note. The indicated automatic valves are used in gas-fired boilers of the floor type. The operation algorithm is absolutely the same for all installations: the element closes the fuel supply when the draft disappears, the flame goes out or the gas pressure in the pipe drops. A detailed overview of the functions of gas automation can be found in the corresponding section of our resource.
The principle of operation of this type of boilers is to double heat the tank with water - directly from the burner and the heat of the flue gases. How a gas-powered water heater functions:
- After opening the valve, gas enters the ignitor, where it is manually ignited by a spark from the piezoelectric button.When the user sets the desired temperature by turning the knob, the main burner is switched on.
- The mass of water is heated from the combustion chamber and the chimney, the condensate formed flows into a special container and gradually evaporates.
- When the set temperature is reached, the thermostat is triggered, the automatics turns off the main burner.
- When cooled or drawn off, combustion automatically resumes.
Clarification. In more modern gas boiler models, such as the Baxi SAG3 100, the ignition system works without a constantly burning igniter. A spark on a special electrode is generated using batteries, as is done on many instantaneous water heaters (that is, gas columns).
Otherwise, the design of the boiler is similar to electric appliances. The cold water pipe is at the bottom, the DHW fence is at the top, and the magnesium anode protects the metal from corrosion. In the floor-mounted version, the connecting pipes exit from the top cover of the tank. The principle of operation of the unit is very intelligibly shown in the English video:
Installation Nuances
Connecting the boiler to the domestic water supply is done by analogy with an electric heater - shut-off valves, a safety non-return valve and a quick emptying system are installed at the outlet. Another thing is the connection of the fuel line, here strict rules that are common for all gas-using installations begin to apply:
- even if the gas is brought into the house, it is necessary to carry out or adjust the project, which will reflect the placement of the device and the connection diagram;
- a full-fledged chimney, built in accordance with the requirements of SNiP;
- the room provides for supply and exhaust ventilation, capable of providing regulatory air exchange (3 room volumes per hour plus combustion air);
- the ceiling height of the room is not lower than 2.5 m, the minimum volume is 15 cubic meters.
Tip. In order not to specially equip the room for a water heater, it is better to immediately put the latter in the boiler room, where ventilation has already been organized and a chimney channel has been made. The installation requirements and the connection procedure are described in more detail in the gas boiler installation manual.
Pros and cons of gas appliances
A natural gas boiler is a specific product. Judge for yourself: in the CIS countries, where this energy carrier is sold at a low price, it is easier to immediately put a double-circuit gas boiler or use a single-circuit one with an indirect heating tank. In Ukraine and EU countries, such a purchase is meaningless.
Since the first option does not provide the required DHW flow rate, and the second requires a decent investment, there is a compromise solution - a flow heater (column). Therefore, given the price of the drive, there are few supporters of gas boilers.
Reference. A high-quality 100-liter hot water tank from the well-known company Baxi will cost 450 dollars. This is comparable to a 24 kW wall-mounted turbocharged boiler of the same brand.
Another significant drawback of the water heater is the problematic installation associated with obtaining permits for the installation of gas-powered equipment. The procedure is tedious and not at all free.
Having enumerated the negative sides of the boilers, we will try to balance them with a positive:
- In terms of heating speed, the devices are record holders among all drives. A tank with a capacity of 100 l is ready for use after 20 ... 30 minutes after starting the burner.
- Water heaters do not need increased attention and frequent maintenance, prevention is recommended to be done annually.
- Low cost of energy for residents of the Russian Federation, Kazakhstan and other CIS countries.
There are questions regarding the reliability of the water-heating equipment. Users often notice burnout of joints near a chimney leading to leaking tanks.Other malfunctions are typical - blockages of the igniter nozzle, failure of the thermocouple and problems in the electrical circuit of the draft sensor.
Indirect heating tanks
If we compare the designs of different water heaters, then an indirect boiler is the simplest and most reliable version of the storage tank for hot water supply. The unit does not produce heat on its own, but receives energy from the outside, from any boiler. For this, a heat exchanger is installed inside the insulated tank - a coil, where hot coolant is supplied.
Clarification. Inexpensive versions of water heaters are equipped with a single heat exchanger that heats the water in the tank. Bivalent models are equipped with 2 coils to connect the unit to several heat sources, for example, a boiler and solar collectors.
The structure of the boiler repeats the previous designs, only without burners and heating elements. The main heat exchanger is located in the lower zone of the barrel, the secondary - in the upper. All nozzles are arranged appropriately; the tank is protected from corrosion by a magnesium anode. How does the "indirect" function:
- From the boiler, the coolant enters the coil, heated to 80-90 degrees (minimum - 60 ° C). The circulation through the heat exchanger is provided by the boiler circuit pump.
- The water in the tank warms up to 60–70 ° С. The rate of temperature gain depends on the power of the heat generator and the initial temperature of cold water.
- The water is taken from the upper zone of the tank, the supply from the highway to the lower.
- An increase in the volume of water during heating is perceived by an expansion tank mounted on the “cold” side and withstanding a pressure of 7 bar. Its net volume is calculated as 1/5 of the tank capacity, at least 1/10.
- An air vent, safety valve and non-return valve are always placed next to the tank.
- In the housing there is a sleeve for the temperature sensor of the thermostat. The latter controls a three-way valve that switches the coolant flows between the heating and domestic hot water.
An important point. The coolant moves along the coil from the upper pipe to the lower, providing a layered loading of the water heater.
Typical strapping scheme
Indirect boilers are produced in horizontal and vertical versions, capacity - from 75 to 1000 liters. There are combined models with an additional heating source - a heating element that maintains the temperature in the event of a stop of the heat generator or burning of firewood in the furnace of the TT boiler. How to properly tie an indirect heater to a wall heater is shown in the diagram above.
Not all wood and gas boilers are equipped with “brains” - electronics that control the heating and operation of the circulation pump. Then you need to install a separate pumping unit and connect it to the boiler according to the scheme proposed by our expert in the training video:
Positive and negative points
Compared to gas boiler models, “indirect” are inexpensive. For example, a wall-mounted unit of the Hungarian manufacturer Hajdu AQ IND FC 100 l costs 290 u. But do not forget: the hot water tank is not able to work independently, without a heat source. It is necessary to take into account the costs of strapping - the acquisition of valves, thermostat, circulation pump and pipes with fittings.
Comment. If you want to assemble a circuit with DHW recirculation, you will need an additional pump, a thermostat and a check valve.
What is a good indirect heating boiler:
- water heating from any heat-power equipment, solar collectors and electric heating elements;
- large stock of productivity for hot water supply;
- reliability in operation, minimum maintenance (once a month warming up to the maximum from Legionella and timely replacement of the anode);
- Boiler loading times can be adjusted, for example, moved overnight.
The main condition for the correct operation of the unit is the sufficient power of the thermal installation.If the boiler is selected purely for the heating system without a reserve, the attached boiler will not let you warm the house or you will be left without hot water.
The disadvantages of an indirect heating tank are a decent size (small ones are less common) and the need to heat the boiler in the summer to provide hot water. These disadvantages cannot be called critical, especially against the background of high performance and versatility of such equipment.
In conclusion, selection recommendations
Homeowners with a limited budget can only choose the right model of electric heating apparatus. This is the most affordable option for the cost of the purchase and installation of equipment. Subsequently, you will have to save energy and put up with the inconvenience of operation - prolonged heating and a small tank capacity.
Which boiler is better to choose based on living conditions and the availability of heating equipment:
- In an apartment building, the easiest and fastest way is to put an electric heater. For the installation of any gas apparatus you need to get permission, and the "indirect man" has nowhere to place and nothing to heat.
- The best solution for a private house is a barrel of indirect heating. By setting the tank to 200-300 liters, you will definitely close the question on domestic hot water.
- If there is not enough space in the furnace room, purchase an indirect boiler in the wall horizontal design.
- When choosing an apparatus of any type, pay attention to the material of which the anode is made. Magnesium elements are being replaced by more durable titanium rods.
- With insufficient boiler power, the connection of an additional tank is contraindicated. There are 3 ways to solve the problem: replace the heat generator, buy an electric drive or install a gas boiler. In terms of comfort / installation cost, the latter option seems preferable.
Note. If the house already has a gas boiler, then obtaining permission to connect additional equipment is simplified. You will have to adjust the existing project and coordinate the documentation with the gas supplier.
The undisputed leader in the rating of storage household heaters is an electric boiler. Popularity is due to the affordable price, simplicity and speed of connection - the device is installed literally in 1 day.