Heating boiler piping schemes for various types of circulation and circuits

Recommendation points

• Connecting the boiler to power supplies
• Single and double-circuit boilers
• Boiler piping diagram with natural circulation
• Boiler piping diagram with forced circulation
• One- and two-pipe heating system
• Collector wiring diagram of the heating system
• Primary-secondary rings
• Emergency circuits

When building an autonomous heating at home, it is important to correctly think over and perform the piping of gas, solid fuel and electric boilers. Let’s look at the possible schemes and piping elements, talk about classic, emergency and specific circuits, as well as about the main equipment of these schemes.

The basic principles of piping a boiler of any design are safety and efficiency, as well as the maximum resource of all elements of the heating system. We will consider various options for organizing heating in order to make a balanced and most suitable decision for a particular case during individual construction.

Connecting the boiler to power supplies

If the boiler runs on gas fuel, then it is necessary to organize a gas supply to it. In the case of main gas supply, this must be done by a gas service employee. If heating is from cylinders, you need to conclude a lease with Gaztekhnadzor, and entrust the installation to a company that has permission for this type of work. All work related to gas is potentially dangerous and this is not the moment when it is worth saving and doing work with your own hands..

1. Heating supply. 2. Hot water for domestic needs. 3. Gas. 4. Cold water to the DHW circuit. 5. Heating return

When using bottled gas, a reducer must be used that combines a group of cylinders

The electric boiler must be connected to the network. The boiler and the terminal box must be grounded, all connections are made with copper wiring with a cross section not less than that specified in the technical passport for the equipment.

A solid fuel boiler is always autonomous and requires only the connection of heating pipes and hot water supply. Electrical connections are only required by automatic control units, if used..

Single and double-circuit boilers

Single-circuit boilers are designed primarily for heating. Only one circuit passes through them, including automation, piping and radiators. An indirect heating boiler can also be included in the circuit to supply hot water to the mixers of washstands, showers and bathtubs. Boiler power is selected with a corresponding power reserve. The expediency of such a connection in most cases is somewhat doubtful, since it disrupts the stability of the functioning of the heating system by a sudden extraction of heat. The problem can be solved by equipping the circuit with a complex control system, which in some models may come with a boiler..

Single-circuit boiler with indirect heating boiler: 1. Boiler. 2. Boiler piping. 3. Radiator. 4. Boiler for indirect heating. 5. Cold water inlet

In a double-circuit boiler, hot water supply, along with heating, is included in the functions of the boiler and constitutes one of its two circulation circuits. More stable operation of both systems is achieved when boilers are equipped with two separate heat exchangers for two circuits. System feature: no hot water storage tank.

Connecting a double-circuit boiler: 1. Boiler. 2. Heating boiler piping. 3. Heating circuit. 4. Cold water inlet

Boiler piping diagram with natural circulation

Natural circulation is based on the laws of physics – thermal expansion of the coolant and gravity, therefore the boiler piping does not include pressure equipment.

In order for the water in the circuit to make a continuous movement, several rules must be observed.

The boiler should be located at the lowest point of the house, preferably in the basement or in a specially equipped pit.

The pipeline from the top point to the heating radiators, and from them to the “return” must be made with a slope of at least 0.5 ° to reduce the hydraulic resistance of the system.

Heating with natural circulation. H – the difference in the levels of the supply and return lines, determines the head in the heating circuit

The diameter of the heating distribution pipes must ensure a water velocity of at least 0.1 m / s and not higher than 0.25 m / s. Such values ​​must be taken in advance and checked by calculation based on the temperature difference at the inlet and outlet (gradient) and the difference in height along the axes of the boiler and radiators (at least 0.5 m).

Boiler gravity circuits can be open and closed. In the first case, an open-type expansion tank is installed at the highest point of the system (in the attic or roof), it also acts as an air vent.

The closed system is equipped with a membrane tank located on the same level with the boiler. Since a closed system does not have direct contact with the atmosphere, it must be equipped with a safety group (pressure gauge, safety valve and air vent). The group is positioned so that the air valve is at the highest point of the circuit.

Natural circulation systems are power independent and are most common where power grids are unavailable or unreliable.

Boiler piping diagram with forced circulation

The impetus for the movement of water in a forced circulation circuit is a circulation pump. The circuits can also be open (with an open expansion tank) and closed (with a membrane tank and a safety group).

The circulation pump is usually installed in a place where the water temperature has the lowest value – at its inlet to the boiler, and is mounted on the same site. The choice of the pump is based on the heating calculation, which shows the required flow rate of the heating medium, and the characteristics of the boiler. Regulation of the heating agent flow is carried out on the basis of the return water temperature by a pulse from the sensor installed at the boiler inlet.

1. Boiler. 2. Security group. 3. Expansion tank. 4. Circulation pump. 5. Heating radiators

One- and two-pipe heating system

The one-pipe system is widespread in old apartment buildings. The water temperature from radiator to radiator is constantly dropping, which leads to uneven heat supply to individual rooms. In a two-pipe system, the coolant is distributed evenly over all radiators, and the loss of temperature enters the second pipe – the “return”. Thus, the two-pipe system provides the house with heat more evenly..

1. One-pipe wiring diagram. 2. Two-pipe wiring diagram

Collector wiring diagram of the heating system

With a large number of heating radiators located on different floors, or when connecting a “warm floor”, the best wiring diagram is collector. At least two collectors are installed in the boiler circuit: at the water supply – distributing, and at the “return” – collecting. The collector is a piece of pipe into which branches with valves are cut in order to be able to regulate individual groups.

Collector group

Example of connecting a heating circuit and a “warm floor” system using a collector group

The collector wiring is also called radial, since the pipes with rays can diverge in different directions throughout the house. Such a scheme in modern houses is one of the most common and is considered practical..

Primary-secondary rings

For boilers with a capacity of 50 kW or more or a group of boilers, which are designed for heating and hot water supply of large houses, the scheme of primary-secondary rings is used. The primary ring is made up of boilers – heat generators, the secondary rings – heat consumers. Moreover, consumers can be installed on the direct branch and be high-temperature, or on the reverse – and called low-temperature.

In order to avoid hydraulic imbalances in the system and to separate the circuits, a hydraulic separator (arrow) is installed between the primary and secondary circulation rings. It also protects the boiler heat exchanger from hydraulic shocks..

If the house is large, then a collector (comb) is arranged after the separator. For the system to work, you need to calculate the diameter of the arrow. The choice of the diameter is carried out on the basis of the maximum productivity (flow) of the water and the flow rate (not higher than 0.2 m / s) or as a derivative of the boiler power, taking into account the temperature gradient (the recommended value? T – 10 ° С).

Calculation formulas:

• G – maximum flow rate, m³/ h;
• w – water speed through the cross section of the arrow, m / s.

• Р – boiler power, kW;
• w — speed of water through the cross section of the arrow, m / s;
• ?t – temperature gradient, ° С.

Emergency circuits

In forced circulation systems, the pumps depend on the power supply, which can be cut off. To prevent overheating of the boiler, which can damage the equipment or even lead to depressurization, the boilers are supplied with emergency systems.

First option. An uninterruptible power supply or generator that will power the circulation pumps. In terms of efficiency, this method is one of the most optimal.

Second option. A small backup ring is being set up, operating according to the gravitational principle. When the circulation pump is turned off, a natural circulation circuit is included in the system, providing heat transfer from the coolant. The additional circuit cannot provide adequate heating.

Third option. During construction, two full-fledged circuits are laid, one works according to the gravitational principle, the second with the help of pumps. Systems should be able to transfer heat and mass during an emergency period.

The fourth way. If the water supply is centralized, then when the pumps are turned off, cold water is supplied to the heating circuits through a special pipe with a shut-off valve (a jumper between the water supply and heating systems).

In conclusion, we suggest watching a video on the rules for calculating a one-pipe heating system for a private house.