Steam heating: pros, cons, device

One of the most important life support systems in our rather unkind climate is heating. There are several different ways to make a heating system. And one of them is steam heating. The system is effective, but it is used very rarely – it has too many disadvantages. 

What is it and how is it different from conventional water systems

Many people believe that steam and water heating are one and the same. This is an erroneous opinion. With steam heating, there are also batteries and pipes, there is a boiler. But it is not water that moves through the pipes, but water vapor. The boiler is required completely different. Its task is to evaporate water, and not just heat it to a certain temperature, respectively, its power is much higher, as well as the requirements for reliability.

Elements of the system

With steam heating, water vapor moves through the pipeline. Its temperature is from 130°C to 200°C. Such temperatures impose special requirements on the elements of the system. First, pipes. These are only metal pipes – steel or copper. Moreover, they should be seamless, with a thick wall.

Secondly, radiators. Only cast iron, registers or finned pipe are suitable. Cast iron under such conditions is less reliable – in a heated state, from contact with a cold liquid, they can burst. More reliable in this regard are pipe registers, coils or a pipe with ribs attached to it – a convector-type heater. Steel is more tolerant of cold water entering its heated surface.

Service life and scope

But do not think that a steel steam heating system will last a very long time. Very hot and humid steam circulates in it, and these are ideal conditions for steel to corrode. Elements of the system quickly fail and fail. Usually they burst in the most corroded places. Despite the fact that steam with a temperature above hundred degrees is under pressure inside, the danger is obvious.

Therefore, steam heating is recognized as dangerous and is prohibited for heating public places and apartment buildings. It is also used in some private houses or for heating industrial premises. In production, it is very economical if steam is a derivative of the technological process. In private houses, steam heating is used mainly in seasonal residences – in dachas. All due to the fact that it normally tolerates freezing – there is little water in the system and it cannot harm, and also because of its efficiency at the device stage (compared to water systems) and the high speed of heating the premises.

Advantages and disadvantages

Steam heating is not the most popular, but it has both positive and negative points. And the advantages are quite significant:

• High heating efficiency. The fact is that the steam in the system does not just heat radiators and pipes to a certain temperature. Due to the large temperature difference, it condenses. And during condensation, 1 liter of steam gives off 2300 kJ of heat. Whereas when the same amount of water cools down by 50°C, only 100 kJ is released. Therefore, a very small number of radiators are required to heat the room. In some cases, a certain number of pipes is sufficient.
• Since steam heating is a small system, it has a low inertia. The room begins to heat up literally a few minutes after the boiler is started.
  

The disadvantages of steam heating systems are even more impressive:

• High steam temperature leads to heating of all elements of the system up to 100°C and above. This leads to the following consequences:
  • very active air circulation in the room, which is uncomfortable, and sometimes harmful (if you are allergic to dust);
  • the air in the room dries up;
  • hot elements of the system are traumatic and must be closed, and pipes too;
  • not all building materials normally tolerate prolonged heating to such temperatures, therefore the choice of finishing materials is very limited (in fact, it is only cement plaster with subsequent painting with heat-resistant paints).
• Simple steam heating has very limited possibilities for adjusting heat transfer. There is only one way to change the temperature – to make several parallel branches and turn them on as needed. The second way is to turn off the boiler when it overheats and turn it on after the room has cooled down. This process is controlled by automation, but this method is far from the most comfortable, as there are constant temperature fluctuations.
• The system is noisy. It makes a lot of noise when moving. In production workshops, this does not really interfere, but in a private house it can be a problem.

As you can see, steam heating is not the best choice, although it is quite inexpensive to set up.

Types of steam heating systems

According to the method of the device, two types of steam heating are distinguished: with a closed and open system. In a closed system, condensate flows into a special receiving pipe, which is connected to the corresponding inlet of the cat. It is laid with a slight slope, so that the condensate flows through the system by gravity.

In an open system, condensate is collected in a special container. When it is filled, it is fed into the boiler using a pump. In addition to the different construction of the system, different steam boilers are also used – not all of them can work in closed systems.

In general, there are steam heating systems with pressure close to atmospheric or even lower. Such systems are called vacuum-vapor systems. What is so attractive about this setup? The fact that at low pressure the boiling point of water decreases and the system has a more acceptable temperature. But the difficulty in ensuring tightness – air is constantly sucked through the connections – has led to the fact that these schemes are practically never found.

Steam heating with low pressure is more common. Available steam boilers for domestic purposes can create a pressure not exceeding 6 atm (at a pressure of more than 7 atm, the use of equipment requires permission).

Wiring types

By type of wiring, steam heating happens:

• With upper wiring (the steam pipeline is located under the ceiling, pipes go down from it to the radiators, a condensate pipeline is laid below). Such a scheme is most easily implemented, since hot steam moves through one pipes, cooled condensate through others, the system is stable.
  

• With bottom wiring. The steam pipe is located at floor level. This scheme is not the best choice, since hot steam moves up through one pipe, condensate moves down, which often leads to water hammer and depressurization of the system.
• With intermediate wiring. The steam pipeline is laid just above the radiators – approximately at the level of the window sills. The system has all the advantages of overhead wiring, except that hot pipes are within reach and there is a high risk of burns.

When laying, the steam pipeline is made with a slight slope (1-2%) in the direction of steam movement, and the condensate pipeline – in the direction of condensate movement.

Boiler selection

Steam boilers can operate on all types of fuel – gas, liquid and solid fuels. In addition to the choice of fuel, it is necessary to correctly select the power of the steam boiler. It is determined depending on the area that will need to be heated:

• up to 200 m2 — 25 kW;
• from 200 m2 to 300 m2 — 30 kW;
• from 300 m2 to 600 m2 — 35-60 kW.

In general, the calculation method is standard – 10 kW of power is taken per 1 square meters. This rule is true for houses with a ceiling height of 2,5-2,7 m. The choice of a specific model follows. When buying, pay attention to the presence of a quality certificate – the equipment is dangerous and must be tested.

Which pipes to use

Temperatures during steam heating can normally only be tolerated by metals. The cheapest option is steel. But to connect them, welding is required. It is also possible to use threaded connections. This option is budgetary, but short-lived: steel quickly corrodes in a humid environment.

Galvanized and stainless pipes are more durable, but their price is not at all modest. But the connection is threaded. Another option is copper pipes. They can only be soldered, they are expensive, but they do not rust. Due to their higher thermal conductivity, they transfer heat even more efficiently. So such a heating system will be super efficient, but also very hot.