Buffer tank: rules for selection, operation and calculation of capacity for a heating system + step-by-step connection diagram

Often, a solid fuel boiler becomes the only option that can be seriously considered as the main source of thermal energy for heating a home. The standard situation for many small settlements and countryside villages is that gas mains have not yet reached every consumer, or laying them directly to the house is associated with prohibitive costs. Electric heating, due to the high cost of electricity, seems unprofitable. But local conditions are characterized by the wide availability and low price of firewood or coal. The solution comes naturally...

Buffer tank for solid fuel boiler

But here’s the problem: the operation of solid fuel equipment is always associated with a certain cyclicity - peak production of thermal energy, even in excess quantities, during the main phase of combustion of the fuel load, with a gradual decrease to almost zero during periods of inactivity. Constantly replenishing fuel in the boiler is inconvenient for a number of reasons, it is unprofitable, and in many models it is completely technologically impossible. Is it possible to make sure that the efficiency of the heating system does not suffer from this pronounced unevenness of energy supply, so that during the burning of the fuel fill a reserve of excess heat is created, which can then be usefully used, and not “thrown down the drain”? Yes, this is quite possible - a similar problem is successfully solved by a buffer tank for a solid fuel boiler.

What is a buffer tank

The equipment is a container with an installed heat accumulator. The container itself accumulates excess thermal energy. The container is equipped with a small coil covered with heat-insulating fabric.

The operation of the equipment begins with loading firewood into it. In this case, the container accumulates excess thermal energy, and then this heat is redirected to radiators. Another very important feature of the device is the support of warm liquid in the radiators.

System nuances

Important! Each heating system with a buffer tank implies the presence of a powerful electric pump, which is necessary for continuous cycling of warm air into the batteries.

• When the power supply is interrupted, the thermal system of the buffer tank stops operating.
• At the same time, the burnt material continues to be processed in the furnace, releasing heat.
• As for the water in the pipes, it begins to heat up even more and reaches a maximum boil.
• If the system is not equipped with a powerful pump that sucks out air, an explosion may occur, which poses a direct threat to human life.

It is also worth noting that the buffer system does not require constant fuel supply. This gives the advantage of not defrosting this system due to sudden extinguishing of the boiler.

System operation

Automatic operation of the buffer unit provides the following advantages:

1. Timely transfer of thermal energy to the coolant;
2. Automatic operation system without human intervention;
3. Continuous heat accumulation;
4. The liquid does not boil if the power supply is interrupted.

Operating principle, scope of application

The operation of a thermal storage device of the simplest type is carried out according to the following principle:

• From the heat exchange circuit of the unit, heated coolant flows into the upper pipe of the container.
• As the boiler operates, the tank is completely filled with coolant heated to the specified value.
• At the same time, from the opposite upper pipe the coolant flows into the batteries of the home heating system and other consumers. However, while the unit is operating, the temperature inside the tank does not fall, but, on the contrary, increases - if, of course, the heat storage device is correctly selected and matches the boiler power and consumer consumption.
• In this case, the coolant cooled in the system enters the lower inlet pipe of the tank, but without mixing with the upper heated layer, it enters the heating circuit of the boiler from the outlet pipe.
• When the tank is filled to the maximum level with heated coolant, the unit turns off.
• Next, the heat accumulator pumps coolant through the system using its own circulation pump.

Operating principle of a heat accumulator indicating the movement of the coolant Source altep.ua

• In this case, the hot phase is gradually replaced by a cooled one. However, a high-quality and well-designed heat storage device is capable of fully maintaining the specified heating of the coolant not only for many hours, but also, if necessary, for several days.

A heat accumulator for a heating system can be used not only in a circuit with a solid fuel boiler, but also with any other that runs on an alternative type of fuel - gas, electricity and even wind, solar and subsoil energy.

The scope of application of a thermal storage device is determined by the following range of its capabilities:

1. The number of connected consumers depends on the presence of independent circuits and can vary from 4 to 20.
2. The heat storage tank can be converted into an electric boiler by installing heating elements through the side flanges.
3. The reservoir can be divided into separate interacting sectors using horizontal overlaps inside.
4. An additional heat exchanger can be installed in the lower area of ​​the tank to increase performance.
5. To provide hot domestic water, a storage tank or an additional heat exchanger can be built into the tank.

Diagram of a combined heating system with a heat accumulator Source evan.ru

Note! A thermal accumulator is especially relevant when the energy resource spent on heat generation has periodic or limited access. An example is solar and wind generators that do not function in cloudy and windless weather. It is also useful when the electric boiler is connected at a reduced rate, which is only possible during certain limited hours of the day.

What does the buffer tank consist of?

The buffer tank for a solid fuel boiler is represented by a metal barrel equipped with an external thermal insulation system. The design of the device is quite simple, but the efficiency of heat transfer is at a high level. Which gives a significant advantage in ideal heating of the room.

Buffer equipment design:

• Heat exchanger in the form of a spiral. Made from stainless steel. It is provided for models that perform several functions in the heating system (solar collectors, heat pump);
• Tank. It is a capacious container, which is made of sheet material coated with enamel. And there are also options for creating a stainless steel tank. In this case, elements intended to connect the heating system with the heat generator depart from the container. The material used to make the container affects the longevity of all equipment;
• Built-in system coil. Helps maintain a constant temperature in the coolant and heats water for domestic needs.

Video description

Video example on how to calculate a heat accumulator:
Next, you need to calculate the mass (volume) of water that would be capable of holding such an amount of thermal energy, using the following formula:

• M = Ke / 0.0012 Δt
• M – mass of water, kg,
• Ke – amount of stored energy, kW,
• Δt – temperature difference between the heated coolant and cooled coolant in the system, °C,
• 0.0012 – heat capacity of water, kW/kg °C.

Substituting the input data into the formula, we get:

100/0.0012 (90-70) = 4166 kg or approximately 4 m³.

However, in practice such large containers are rarely used. Therefore, in order to reduce the costs of their installation and maintenance, downtime can be reduced by half, and the coolant cooling level can be reduced to an acceptable 500C. Then, to maintain comfortable heat in a house with good thermal insulation, a capacity of 1000 liters will be sufficient.

Pros and cons of a buffer tank

Before purchasing, you should also pay attention to customer reviews about this equipment.

pros

1. The equipment is protected from overheating;
2. The boiler releases its full thermal energy;
3. Smooth operation of the equipment, which allows you to warm up the room in an equal proportion;
4. Constant hot water;
5. Automatic heating system;
6. Increasing the efficiency of equipment by installing its system.

Minuses

1. The tank takes up a lot of space in the room;
2. A separate room is required for mounting the container;
3. Problematic delivery of equipment due to the above symptoms;
4. It takes time to establish stable operation of the equipment;
5. High cost of equipment compared to the boiler itself.

Criterias of choice

When choosing a heat accumulator for a home heating system, the following criteria should be taken into account:

• Capacity of the container. It is calculated taking into account the characteristics of the system, the power of the unit, and the consumption of domestic hot water.
• Dimensions and weight. They must correspond to the strength of the base on which they will be installed, as well as the characteristics of transportation and installation work.
• Limit pressure level. It must be no lower than the same parameter in the system. They determine the thickness of the walls, the material from which they are made, as well as the geometry and design features of the tank.
• Case material. Products made from carbon steel alloy are cheaper, but also have a shorter service life due to their susceptibility to corrosion. Stainless steel models are more expensive, but are durable.
• Additional heat exchangers. The number is determined by the presence of connected circuits and the complexity of the circuit.

The main feature of the difference between heat accumulators is capacity Source termico.com.ua

• Functional. Depending on the capabilities, manufacturers equip their products, in addition to the basic parameters, with various additional functions - installation of heating elements, installation of control and measuring equipment, installation of automation and safety devices, such as, for example, air valves, thermostats, etc.
• The quality of the thermal insulation layer. Not only the thickness of the coating is taken into account, but also the type of material used. The longer the tank stores heat, the more cost-effective it is in a private heating system.

On a note! It is better to purchase a thermal storage device only at a specialized retail outlet. The product must be branded, have a certificate, a guarantee and a full instruction manual.

Boiler capacity

The amount of heat that will be supplied at the appropriate power of the heating device depends on the parameters of the equipment’s capacity. If the equipment produces 35 kW/hour, then the volumetric capacity data must be exceeded up to 30 times. It is worth paying attention to additional factors when calculating capacity.

• Firstly, the heating battery in the buffer tank is installed in such a way that it does not affect the system in any way at a temperature of -30 degrees.
• In this situation, the boiler will continue to operate, but only bypassing the buffer installation.
• When the external temperature rises, the heat accumulator begins to work, which accumulates all the excess heat.

Power is calculated based on natural conditions. If we take a temperature of -29 C, then the device will lose 33 kW in one hour and the power must correspond to this temperature regime.

The size of the room also affects the buffer heating boiler. For large areas, appropriate container sizes are purchased. For small rooms it would not be advisable to buy a large boiler.

Tips for buying a buffer tank

Before purchasing, it is advised to contact professionals who work with heating devices. They will take into account the nuances of the room for which the buffer boiler is purchased. And they will help you make the right and optimal choice on all counts.

If you have to make a purchase yourself, it is recommended to pay attention to such components of the buffer unit as:

• Container volume;
• Heating system pressure;
• Availability of an auxiliary heat exchanger;
• Weight and external characteristics;
• Functionality of the device in case of installation of additional elements.

Prices: summary table

Connection rules

Buffer equipment will delight you with its long service life if the following rules were taken into account when connecting it:

1. Availability of water purification filters;
2. For main heat supply, a locking mechanism is required;
3. Connections in the system must be flanged or threaded;
4. The presence of a valve for air removal;

The presence of a pressure gauge and a safety valve on the heat exchanger.

Online calculator

*If the calculator shows 0 (zero), it means you have no excess energy to accumulate.

Explanations:

The rated power of the boiler is indicated by the manufacturer. If the documents for the equipment have not been preserved, you can find the specifications on the Internet.

The power needed to heat your home. It is calculated by specialists using a complex form, which includes: the volume of the room, the heating system, and the energy efficiency of the entire house.

Supply and return temperatures. If the system does not have thermometers installed, it can be removed with any heat remover.

Photos of the best buffer tank models