Boilers for heating: what is the best heating boiler?

With the first cold weather we have to return to the city – our climate is not that we can live in a cold house. Meanwhile, to make the heating of the house – not such an impossible task, especially since everything that this requires, in a large variety on the market.

And having a warm country house, you can get out there for the weekend at any time – regardless of the season, and if the house is not too far from work, and even live there all year round.

The problem of creating a heating system for a single house is not new. But if previously it concerned only a limited category of owners of private houses, living mostly in rural areas, but now, when we almost all have dachas or cottages, it has become universal.

Moreover, with the advent of turbo burners, the functioning of which eliminates the need for a traditional chimney, autonomous heating systems began to be used for individual apartments in multi-storey buildings, and we, not by hearsay familiar with the unreliable and inflexible system of central heating, do not need to explain the advantages of independent systems.

Moreover, as shown not only by experts’ calculations, but also by concrete examples of apartment heating in some areas of New York and New York region, the lack of costs for heating the coolant in pipes which are many kilometers long, besides being in such a deplorable condition that accidents happen one after another, provides several times more savings. Savings, both as an energy carrier that is a national asset, and as a consequence of our individual heating costs.

The possibilities of the liquid system

The most common heating systems, allowing year-round heating of large areas, are liquid heating systems using heating boilers. The principle of operation is simple: the energy released in the boiler during combustion of fuel or heating elements with the help of a heat exchanger is transferred to the heat carrier usually this role is water which flows through the pipes into the radiators installed in the room .

Such a system is the most efficient, and although its installation is quite complex and not cheap, it is simple and economical in operation. For comparison: the use of several electric convectors for heating the house will lead to much higher power consumption, and will not do without additional work during installation – because of the large capacity of devices needed to heat the whole house, the electrical wiring will certainly have to be changed .

By the way, you can “power” the hot water not only radiators, but also a system of “warm floor”, which allows you to achieve the most efficient distribution of temperature. And another important advantage of this system is preserving the freshness and humidity in the room, since the temperature of the radiators not to mention the “warm field” does not exceed 50-70 ° C.

To live in complete comfort, the house must have a system for hot water in addition to the heating system that is the very services for which in a city apartment we are now sent a separate bill with a very tidy figure . You don’t need a water heater for hot water, but you don’t need one if you have a boiler: the boiler is good for both tasks.

This is done in two ways: either by using a two-circuit boiler, representing 2 structurally related heat exchange units one node – for heating, the other – to obtain technical hot water , or by connecting single-circuit heating boiler to a storage boiler built-in device or external .

Of course, the option with a two-circuit boiler is more compact, but you should keep in mind that for the hot water supply of several points of water eg, taps in the kitchen and bathroom, shower , even with a two-circuit boiler can not do without the storage boiler.

Boiler – the heart of the system

It is obvious that the central place in this system is taken by the boiler. Ideas of those for whom the boiler is associated with something very large and certainly grimy, have long been outdated: Modern ergonomic and compact design of the boiler can easily find a place for it in the room, and wall mounted boiler in appearance at times and not distinguishable from the water heater. If you are short of space, you can choose a model designed for outdoor installation such boilers can operate at outside temperatures down to -15 ° C .

Different energy carriers

Although boilers can run on a variety of energy sources, not all of them are available. So, in areas where there is neither electricity nor gas main, the choice is only between the solid coal, wood, peat or liquid diesel fuel. Boilers, working on solid fuel, have low efficiency and are not very convenient in operation the fuel has to be fed manually , so they are not popular.

Unlike solid fuel boilers, the efficiency of liquid fuel boilers reaches 92%, but their use is limited by the rather high costs both start-up and operational and the complexities of installation and maintenance: it is necessary to agree with the fire inspection, equipment of a separate room with a hood, conduct systems and cleaning of fuel, boiler regular cleaning from ash and soot. However, the liquid fuel burner is easy to replace the gas burner – such a boiler can be used even if the area will be gasified.

Gas is the cheapest energy carrier, and gas boilers with high efficiency can have unlimited capacity. For their installation also requires permission of the gas service and a special room with an area of not less than 8 m2 with a window and output to the street, and the boiler itself must be equipped with automatic, which does not allow gas leakage.

Electric boiler does not need a separate room, since the energy required for heating is not released during combustion, but during the passage of current through the heating element, its connection will require a separate reinforced electric wiring, and with a capacity above 9 kW connection is permitted only to the three-phase network.

Electric boilers are safe, environmentally friendly and easy to operate, but the boiler capacity due to the high cost of energy does not exceed 15 kW, and the heating element has a limited lifetime.

We could mention the combined boilers, working on different types of fuel, but it is probably only for the sake of completeness, as there is no special need to work on different types of fuel, and the cost of such boilers – both start-up and operational – is very high.

Firstly it is necessary to define

A wide range of models of boilers offered in the market allows everyone to make the best choice. But first we must determine what exactly you need, depending on specific conditions, your capabilities and requests: the type of fuel, the area of heated space, the number of water outlets.

Let’s estimate the power

Estimate the power required to heat the room, you can be based on a simple ratio, according to which for heating 1 m2 of area requires 100 watts. Of course, this is just a rough estimate based on the assumption that the room is well insulated and no more than 3 m high. For rooms with multiple windows, corners or adjacent to the unheated room, 1 m2 will need at least 150 watts, but the exact calculation, taking into account all the features of the room can only make professionals.

Boilers with capacity from 20 to 45 kW are most popular in our country, which corresponds to the typical size of most private houses. Basically, these are gas boilers that can have both wall mounted and floor standing versions.

The power of wall hung gas boilers that do not occupy the floor area and are easily located in the kitchen or bathroom – from 10 to 35 kW, which is more than enough to create a comfortable environment in a room with an area of 50-350 m2.

Floor standing gas boilers, on the contrary, require additional space for installation, but this drawback is more than offset by their high power, reaching 60-80 kW.

How much hot water do you need for total comfort?

If you are going to install a boiler to kill two birds with one stone, that is to solve both problems – heating the house and providing it with hot water, you must also estimate how much hot water you need.

Two-circuit gas boilers, working in the flow mode, have a capacity t. e. number of liters of water heated in 1 minute from 10 to 20 liters per minute. – Such flow is enough not only for washing dishes and washing, but also for showering and even bathing for reference: a dense stream from the faucet flows at a rate of 6-7 l min. .

However, choosing a variant with a hot water preparation system, do not forget to recalculate the power: it will now be determined by the larger of the two components – for heating and for heating technical water.

The rule of thumb for calculating the power required for heating in flow mode is also very simple: the power is approximately equal to twice the capacity value when heating water at 25 ° C and tripled when heating water at 35 ° C given that usable hot water has a temperature of about 40 ° C, and the cold water temperature varies depending on the season .

In practice, the two-circuit boiler is arranged so that the heating is turned off during the preparation of hot water. This so-called “priority scheme of hot water preparation” does not entail any inconvenience to the consumer: the heating system is so inert, that switching off its heating for a short period of time will not be noticeable.

If your “appetites” are so great that you want to have hot water in all faucets at the same time, it is preferable, as already mentioned, to have a boiler with built-in or external storage boiler, which stores pre-prepared hot water. Boilers are also equipped with wall hung boilers, and floor standing gas boilers usually have a built-in boiler capacity of 60 to 150 liters, which allows you to quickly fill the bath or long soak under the abundant shower jets.

Features of gas boilers

Boiler is a very complex unit, and its design differs significantly depending on the type of fuel it is designed for. Our further consideration will concern only gas boilers – the most common due to a number of significant advantages: cheapness of fuel and absence of problems with its transportation and storage, high efficiency and high power. Nevertheless, even with this limitation, the choice of a suitable model due to the many differences in components, materials used, control and monitoring systems remains very difficult.

Materials

Cast iron or steel is used for the production of boiler bodies. Cast iron is characterized by great corrosion resistance, and thanks to the high thermal conductivity coefficient the heat is transferred to the water evenly along the entire surface of the boiler.

However, cast iron is not elastic enough, so it does not tolerate large temperature differences, as well as low water quality. The design of cast iron boilers is sectional, which facilitates transportation and installation, and is convenient for maintenance. Steel boilers have good elasticity, which ensures their reliability, they are lighter and cheaper than cast iron ones, but corrosion is a constant threat to them.

Cast iron is also used in the manufacture of heat exchangers, but copper heat exchangers are heated faster low inertia due to the highest among the materials used in boiler construction coefficient of thermal conductivity .

Copper heat exchangers are given a special surface coating to protect them from corrosion, and the inadequate heat resistance of copper, which can sometimes cause burn-out, is overcome by covering them with silicone and aluminium. Stainless steel heat exchangers are often used as well.

Assemblies

The most important node, where the energy supplied to the heat carrier is actually released, is the combustion chamber, which can be open or closed. In the open chamber, the air needed to maintain the combustion process is taken directly from the room in which the boiler is installed, and the combustion products are exhausted through a traditional chimney under the influence of natural draught produced due to their higher temperature compared to the ambient air. The room in which the boiler with a closed combustion chamber is installed must have a constant supply of air, since the combustion of 1 cubic meter of natural gas requires 12-15 cubic meters of air.

In a closed chamber – the draft is forced: the output of combustion products and air inflow is carried out with the help of a built-in fan through the smoke and air intake system running into the wall such a system may consist of either two separate pipes, or coaxial, when one pipe is inside the other . In this case, the room air is not used, so there is no need for additional air supply, and most importantly, the oxygen contained in the room air is not burnt. By the way, to spend such a coaxial chimney is easier, but it should be taken into account that without electricity it will not work.

The choice of type of chamber depends on the situation: if the boiler is installed in a room already equipped with a chimney, it is easier and cheaper to use a boiler with an open combustion chamber, if there is no chimney – boiler with a closed chamber is preferable.

The burners themselves can also be of two types: atmospheric or supercharged in other words – fan or turbo burners . In the atmospheric burners, the air is mixed with the gas supplied under the pressure of the gas main, due to the natural draught of the chimney. In the supercharged gas is mixed with the air blown by a fan, so the boilers, equipped with such burners, emit a characteristic hum, which, however, is easy to eliminate installation of sound insulation.

Control

Modern gas boilers, equipped with all kinds of automation, are extremely easy to manage. The boiler is started by means of a piezo or electric ignition. In the first case to start it is enough to press the button on the control panel, and the on off boiler with electric ignition is automatic at the moment of gas supply or its termination.

The gas flow rate on the modulating burner used in most modern boilers is controlled by the water flow, so that the temperature of the outgoing stream remains constant regardless of the pressure in the water supply network, or whether other taps are open.

The control system of burner output, which allows to change it stepwise from 30-40% to 100%, not only improves comfort, but also reduces the probability of scale formation in the heat exchanger, the growth of which increases sharply when the water temperature reaches 65 degrees. In practice, if the boiler operates at maximum output when heating water, the output is automatically reduced further on, when it is only necessary to maintain the temperature at the reached level. This in turn reduces the frequency of switching on and off of the boiler, which significantly increases its service life.

Water temperature is set by the thermostat built into the system, which regulates heating in both circuits. However, due to the inertia of the system, the temperature in the heating circuit is better to be set with an additional room thermostat that automatically adjusts the boiler output to the temperature fluctuations in the room.

But the best option is to use weather-controlled automatic devices that work according to a signal from a sensor located outside the room, so the temperature in the room will always be as comfortable as possible, no matter what is going on outside, and without any effort on our part. In addition, the real gas savings achieved in this case is quite significant.

Safety

A safety system serves to ensure both the safety of the user and the protection of the boiler components.

For the user, maximum operational safety is guaranteed by two control systems: draught gauge and ionisation flame detection. The draught sensor monitors the complete removal of combustion products, and if this is not done for any reason due to a clogged chimney or fan failure , the gas supply will be instantly cut off.

The system reacts in the same way if the burner does not light up or goes out – no matter for what reason: the lack of water in the system or a faulty pump that does not provide the necessary amount of flow.

It will be possible to find the cause of the situation will be in a safe situation, and a significant help in this will have an electronic system self-diagnostics, allowing to determine up to 10 types of possible problems: no gas supply and blocking the output of combustion products, lack of water or overheating in the heating circuit, failure of the temperature sensor in one or both circuits ..

For the trouble-free operation of all elements of the boiler, there are various safety precautions. A safety thermostat monitors the overheating of water and heat exchangers and switches the heating off when the critical temperature is reached. In the opposite case, if the temperature falls too low to cause freezing of the water in the system, the boiler heating is automatically activated.

Water pressure is controlled by a pressostat, which activates in the event of insufficient pressure, and a safety valve, which does not allow its exceeding in the heating circuit. To prevent the pump and the three-way valve from jamming under the influence of limescale deposits, the water is run through the system every 24 hours in addition, an electronic protection or magnetic treatment is used to prevent scale formation and a particle filter is installed on the cold water inlet. And to ensure that the boiler electronics is not triggered by extraneous sources, in abundance present in any house, a radio interference filter is installed in it.

Adaptation to American conditions

Since the vast majority of boilers on the market “of foreign origin”, it is very important that they are adapted to the conditions in which they will operate in our.

First of all it concerns the gas pressure in the network. The thing is that while most of European manufacturers test the burner at nominal gas pressure of 18-20 mbar, the default value of our rated pressure is 13 mbar and sometimes it is half as much . At such pressure, the boiler does not develop the rated output and therefore it is not suitable for the intended application.

At least 90 % of the maximum boiler output is achieved at 13 mbar, provided that the setting is correct. What’s more, some models fire up steadily and work even when the pressure drops to 2 mbar, which is not uncommon in our unstable gas grids.

Unfortunately, fluctuations are also characteristic of water and electricity networks, so the adaptation of boilers should take into account the instability of these parameters as well. Many problems are caused by poor water quality: boilers should be equipped not only with filters for impurities, but also with a system of protection against salt deposits.

And the last thing you should pay attention to – the size of transitional elements and connections used in the connection and installation of devices. Failure to match the gas fittings of imported devices to American standards will force the buyer to make complex, unsafe and expensive welding.