Which boiler to choose – comparison on the principle of operation, complexity of connection and price

Selecting the ideal boiler for your house is an important choice that will affect your comfort level, energy economy, and even your pocketbook. It’s important to carefully consider your options because there are many different types of boilers on the market, each operating on a different set of principles and offering varying degrees of installation complexity and cost. This post will go over the important things to think about when choosing a boiler to heat and properly insulate your house.

Boilers are available in various varieties, each with a unique way of working. Making an informed decision requires an understanding of these differences. Conventional boilers, including system and conventional boilers, heat water and then distribute it to radiators or underfloor heating systems. However, combination boilers, or combi boilers for short, heat water as needed, doing away with the need for a separate hot water cylinder. We will discuss the benefits and drawbacks of each type in more detail.

The decision-making process is heavily influenced by the complexity of the connection, aside from the operating principle. Making sure a boiler blends in perfectly with your current heating system is just as important as choosing the appropriate unit when installing one. Because conventional and system boilers have separate hot water cylinders and expansion tanks, which complicate installation, they usually take up more space. On the other hand, combi boilers are a popular option for smaller homes or properties with limited space because of their small size and ease of installation.

Cost is yet another important consideration when selecting a boiler. The price of the unit itself can change based on a number of variables, including size, brand, and installation complexity. Combi boilers may be more expensive initially than conventional boilers, but over time they can save money on maintenance and energy costs because of their efficiency and compact design. To choose the most economical course of action for your house, you must consider the potential savings over time in addition to the initial investment.

Principle of Operation	Complexity of Connection
Comparison of different types of boilers based on how they work: gas, electric, or oil boilers.	Assessment of the difficulty in setting up each type of boiler, considering factors like plumbing and electrical work.

What is important to know about an electric boiler

The following components are part of the water heater construction depicted in the diagram below:

• external metal casing of cylindrical or rectangular shape, equipped with a wall mounting bracket;
• an inner tank made of enameled or stainless steel;
• heater – heating element with a capacity of 1.5-2.5 kW, installed vertically in the lower area of the tank;
• magnesium or titanium anode;
• Thermostat – remote or mounted in the heating element;
• cold water supply and hot water extraction pipes;
• thermometer;
• obligatory element of piping – a two-in-one safety check valve is usually included with the heater;
• The controls are located on the bottom end of the cylindrical tank or on the front panel of the rectangular version.

Note: Polymer insulation fills the gap between the inner water tank and the outer casing. More expensive models use "dry" type heaters with ceramic limescale protection, while cheaper models use standard electric heaters in tubular form.

How an electric heating boiler operates:

1. 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 pipe that exits to the bottom of the tank.
2. Next is the switching on and heating of the mass of water by the heating element. When the temperature reaches the set or maximum value, the thermostat switches off the electric heater.
3. Water is drawn through a tube ending in the upper zone of the tank, where the water temperature reaches the highest point. At the same time, the tank is fed from the water supply system via the bottom tube.
4. During the operation of the DHW system, the water in the tank cools down and the thermostat automatically switches on the heating element. If there is no water supply, the contents of the tank are periodically heated by a heating element in order to maintain the desired temperature.

Citation. Most boilers have a maximum heating temperature of 75 degrees, although 55 degrees Celsius is advised to conserve electricity. A sensor that senses overheating and turns off the heating element when the temperature reaches +85 °C is present in certain models.

Installing a magnesium anode next to the heating element is necessary because the metals that make up the bodies of the tubular heater and the tank are different (copper, steel). The intention is to keep the tank’s walls from being destroyed by electrochemical corrosion. The following video provides a detailed explanation of the water heating boiler’s mechanism and operation:

Wiring diagram

It is simple to install and connect the electric water heater to the pipes, and if preferred, it can be done on its own:

1. Fix the tank on the wall using the standard brackets. Room for the boiler – kitchen, bathroom or boiler room.
2. Connect the appliance to the water supply and the DHW network, following the diagram.
3. The power supply is provided by an ordinary socket with an earthing contact.

Allow us to elucidate the purposes of a few piping components. The "2 in 1" valve, which is installed at the boiler’s inlet and handles three functions, is crucial.

• prevent the vessel from emptying back into the water supply pipe;
• Release excess pressure resulting from the heating and expansion of the liquid inside the closed tank;
• forced drainage.

Additional shut-off valves are required for simple water heater maintenance and cleaning. It is necessary to empty the tank in order to remove the useless magnesium anode. Because of the small cross-section of the standard valve’s spout, it takes too long to discharge; it is preferable to install a tee and an additional valve.

The fast drainage scheme is particularly important for summer houses that have sporadic heating. Every time the owners leave the house in the winter, they have to empty the system to prevent the water supply from defrosting.

When a heater breaks down and needs to be removed and repaired without removing the water lines, American and cut-off taps come in handy. The necessity of a filter at the building inlet is evident to any prudent homeowner.

Advantages and disadvantages

While enumerating boiler benefits, we will omit some features that are present in all storage heaters. Advantages of electric devices:

• affordable price of the water heater;
• easy installation and piping;
• permission for connection to the power grid is not required;
• relatively small dimensions;
• execution of the units – vertical or horizontal, wall-mounted or floor-mounted;
• maintenance – not more often than once in 2-3 years, can be done independently.

Accreditation. An Ariston model SB R 100 V tank water heater with a capacity of 100 liters costs 120 u.е. Chinese equivalents will be even less expensive.

Flushing, cleaning, and magnesium anode replacement are all part of boiler maintenance. The heating element’s copper and the tank’s metal will succumb to electrochemical corrosion if you miss the anode’s critical wear point. A corroded tank needs to be replaced; repairs are not possible. Likewise with a heating element that has burned out.

Let’s talk about the drawbacks of electric appliances now:

• in terms of heating speed (about 2 hours), the products lose out to gas and indirect units of identical volume;
• consumption of expensive energy carrier;
• impossibility to check the condition of the anode without disassembling the unit;
• Limited capacity.

Water hardness can affect electric heaters. The anode "melts" faster and the layer of scale on the heating element’s walls and housing gets thicker when the concentration of magnesium and calcium salts increases. An annual cleaning resolves the problem.

Choosing the right boiler for your home involves considering factors like how it works, how easy it is to install, and its price. There are different types of boilers, each operating on various principles such as gas, electric, or biomass. Gas boilers are common, efficient, and relatively straightforward to connect, but they require a gas supply. Electric boilers are easy to install and don"t need a flue, but they might be more expensive to run. Biomass boilers use organic materials like wood pellets, offering sustainability but requiring more maintenance. Price-wise, gas boilers are often the most affordable upfront, while electric boilers might have a higher initial cost but lower long-term expenses. Your choice depends on your home"s setup, your budget, and your environmental preferences.

Gas storage water heaters

The unit’s exterior features, including its cylindrical body, pipe connection fittings, and thermometer on the front, give it a vertical version of the electric storage unit look. There is a chimney spigot only at the top, and there is an extra section with gas equipment at the bottom.

There are notable distinctions in the internal construction of a boiler that uses liquefied or natural gas:

• In the lower additional section there is an open (atmospheric) combustion chamber and a gas burner;
• the tank is penetrated by a vertical flame tube that discharges the combustion products to the outside through an external spigot with a hood;
• inside the flue duct there is a draught sensor and a turbulizer, which makes the glowing gases move slower and actively exchange heat with the water tank;
• a condensate collection tank is located below the burner;
• The fuel supply is controlled by a safety automatism – a non-volatile gas valve from SIT Group or another manufacturer;
• the tank has a submerged sleeve for the thermostat sensor connected by capillary tube to the safety valve.

Note: Floor type gas boilers use these automatic valves. The operating algorithm for every installation is the same: when the draught stops, the flame goes out, or the gas pressure in the pipe drops, the element cuts off the fuel supply. The relevant portion of our resource contains a thorough description of the features of gas automatics.

This kind of boiler works on the principle of heating the water tank twice: once from the burner and once from the heat from the flue gases. The operation of the gas-fired water heater:

1. After opening the valve, the gas flows to the igniter, where it is manually ignited by a spark from a piezoelectric button. When the user sets the desired temperature by turning the regulator, the main burner is switched on.
2. The water mass is heated from the combustion chamber and chimney, the resulting condensate flows into a special container and gradually evaporates.
3. When the set temperature is reached, the thermostat is activated and the automation switches off the main burner.
4. The combustion is automatically restarted in the event of cooling or water intake.

To be clear. Modern gas boiler models, like the Baxi SAG3 100, have an ignition system that functions without an igniter that burns continuously. As with many flow water heaters (also known as gas-fired boilers), a spark is created on a specialized electrode by means of batteries.

Other than that, the boiler’s design is comparable to that of electric appliances. The DHW intake is located at the top, and a magnesium anode shields the metal from corrosion. The cold water pipe is located at the bottom. The connection spigots on the floor version emerge from the tank’s top cover. The English-language video provides a very clear demonstration of the unit’s operating principle:

Installation nuances

Similar to an electric heater, the boiler must be connected to the home water supply. At the outlet, there is a quick emptying system, a safety check valve, and a shut-off valve. Another item is the fuel line connection, where stringent guidelines that apply to all gas-using installations come into effect:

• even if gas is brought into the house, it is necessary to execute or correct the project, which will reflect the location of the appliance and the connection scheme;
• need a full-fledged chimney, built in accordance with the requirements of SNiP;
• the room is provided with a supply and exhaust ventilation capable of ensuring a standard air exchange (3 room volumes per hour plus combustion air);
• ceiling height of the room – not lower than 2.5 m, minimum volume – 15 cubic meters.

Advice: It’s best to install the water heater right away in the boiler room, where the chimney channel and ventilation are already set up, to avoid having to set aside a separate space for it. The gas boiler installation handbook contains more specific installation requirements as well as connection order information.

Pros and cons of gas appliances

One particular product is a natural gas-powered boiler. See for yourself: it is simpler to install a two-circuit gas boiler right away or to use a single-circuit with an indirect heating tank in the CIS countries, where this energy carrier is sold at a low cost. This kind of purchase is useless in the EU and Ukraine.

Flow heaters (columns) are a compromise solution because the first option won’t give the required flow of DHW and the second requires a sizable investment. Thus, there aren’t many people who support gas boilers considering the cost of the storage tank.

Aid. An excellent 100-liter tank water heater from the reputable brand Baxi will set you back 450 u.е. This is similar to the same brand’s 24 kW wall-mounted turbo boiler.

Problematic installation, which is related to the registration of permits for the installation of gas-using equipment, is another major drawback of the water heater. The process is very time-consuming and not free.

After enumerating the drawbacks of boilers, let’s attempt to counter them with their advantages:

1. In terms of heating speed, the units are the record holders among all storage devices. The tank with a capacity of 100 liters is ready for use 20…30 minutes after starting the burner.
2. Water heaters do not need much attention and frequent maintenance, preventive maintenance is recommended to be done annually.
3. Cheapness of energy carriers for residents of the Russian Federation, Kazakhstan and other CIS countries.

Water-heating equipment’s dependability is called into question. Users frequently report burning joints close to the flue pipe, which causes tank leaks. Other common errors include clogged igniter nozzles, thermocouple failure, and issues with the draught sensor’s electrical circuit.

Indirect heating tanks

When comparing the various water heater designs, the indirect boiler is the most straightforward and dependable type of DHW storage tank. The unit gets its energy from an external source, such as a hot water boiler, rather than producing heat on its own. This is accomplished by installing a heat exchanger—a coil—within the insulated tank, which receives hot coolant.

To be clear. The water in the tank is heated by a single heat exchanger in less expensive models of water heaters. Two coils are included in bivalent models to allow the unit to be connected to multiple heat sources, like solar collectors and a boiler.

The boiler’s structure is a replication of earlier designs, minus the burners and heaters. The barrel’s lower zone contains the primary heat exchanger, while the upper zone contains the secondary heat exchanger. Every spigot is positioned correctly, and a magnesium anode guards against corrosion inside the tank. The way the "indirect" works

1. From the boiler into the coil comes the coolant heated to 80-90 degrees (minimum – 60 ° C). Circulation through the heat exchanger is provided by the boiler circuit pump.
2. The water in the tank is heated to 60-70 ° C. The rate of temperature rise depends on the power of the heat generator and the initial temperature of cold water.
3. The water intake comes from the upper zone of the tank, the supply from the mains – in the lower zone.
4. The increase of water volume during heating is taken by the expansion tank installed on the "cold" side and withstanding the pressure of 7 bar. Its useful volume is calculated as 1/5 of the capacity of the tank, minimum – 1/10.
5. An air vent, safety valve and non-return valve must be installed next to the tank.
6. The housing has a sleeve for the temperature sensor of the thermoregulator. The latter controls a three-way valve that switches the flow of coolant between the heating and DHW branches.

Important point. The heat transfer fluid loads the water heater layer by layer as it travels through the coil from the top pipe to the bottom pipe.

Typical piping scheme

There are two types of indirect boilers available: horizontal and vertical, with capacities ranging from 75 to 1000 liters. Certain combined models come equipped with an extra heating source called TEN, which keeps the temperature constant in the event that the heat generator is turned off or wood is burned in the TT-boiler’sfurnace. The diagram above illustrates how to wire an indirect heater to a wall heater correctly.

Not every gas or wood boiler has "brains"—electronics that regulate the heating and circulation pump. Next, in accordance with the plan our expert presented in the tutorial video, a separate pumping unit must be installed and connected to the boiler:

Positive and negative aspects

"Indirect heaters" are less expensive than gas boiler models. For instance, the Hungarian manufacturer Hajdu AQ IND FC 100 liters wall-mounted unit costs 290 u. е. Remember, though, that a hot water tank requires a heat source to function on its own. It is necessary to factor in the cost of the plumbing, including the valves, thermostat, circulation pump, and pipes and fittings.

Note: An additional pump, thermostat, and check valve are required if you wish to construct a scheme that uses DHW recirculation.

What makes an excellent indirect water heater?

• water heating from any heating equipment, solar collectors and electric heating elements;
• large reserve of DHW capacity;
• reliability in operation, minimum maintenance (once a month heating up to maximum legionella and timely replacement of anode);
• the boiler loading time can be adjusted, e.g. by moving it to the night.

The thermal unit must have enough power in order for the unit to operate as intended. The associated boiler won’t heat the apartment or provide hot water if it is only set up for the heating system and has no reserve.

A decent size (smaller ones are installed less frequently) and the requirement to heat the boiler in the summer to provide domestic hot water are the drawbacks of the indirect heating tank. These drawbacks are not severe enough, especially considering the equipment’s excellent performance and adaptability.

Your comfort level, energy efficiency, and financial situation can all be greatly impacted by your choice of boiler for your house. We have examined the three most important variables in this comparison: cost, connection complexity, and operation principle.

First and foremost, it’s critical to comprehend the operating principle. Conventional boilers heat and store water in a storage tank so that there is a constant supply of hot water when needed. Conversely, combi boilers heat water only when it is needed, doing away with the need for a storage tank and frequently freeing up space in your house. When choosing the right type of boiler for your home, take into account the hot water usage patterns and available space.

The connection’s complexity is a critical factor to take into account next. A boiler’s installation involves a number of factors, such as your home’s layout, the state of your current heating system, and any applicable regulations. Because traditional boilers require a storage tank and related pipework, installation may be more involved. On the other hand, because combi boilers do not need a storage tank or related pipework, they are usually easier and faster to install. To determine your unique installation requirements, it is imperative that you speak with a licensed heating engineer.

And lastly, a big part of the decision-making process is price. Because they are typically less expensive up front, traditional boilers are a desirable choice for people on a limited budget. However, because of their increased efficiency and capacity for on-demand heating, combi boilers can result in long-term cost savings on energy bills. For your home, the most cost-effective option must be determined by balancing the potential long-term savings against the initial investment.

In conclusion, take price, connection complexity, and operation principle into account when selecting a boiler for your house. Consider the hot water demands, space limitations, and financial situation of your home to decide if a combi or traditional boiler is best for you. To guarantee a safe and effective installation, seek advice from a certified heating engineer. You can benefit from optimal comfort and energy efficiency in your home for many years to come by making an informed decision.

Video on the topic

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