Rising energy prices lead to a steady increase in utility tariffs. The deterioration of boiler equipment and dilapidated lines reduce the reliability of centralized heat supply. There are autonomous options for heating a country house: the right choice of boiler will reduce dependence on external factors, increase the efficiency and functionality of the system. Foreign and domestic manufacturers produce heat generators for private homes. Generators run on electricity, solid, liquid and gaseous fuels. Each type of energy resource has its own advantages and disadvantages, however, the choice of the boiler depends on the available fuel.
Options for heating a country house: how to choose a boiler
How to choose a boiler for heating a private house? Individual construction presupposes the existence of a project which includes the heat engineering design of the building. Schemes, detailing and recommendations of designers on the arrangement of the heating system constitute the engineering part of the document. If there is no ready-made solution, then the article offers the reader the principle of self-selection of boiler equipment.
Generator power must correspond to the heat load of heated premises. Deviations lead to uneven heating of heating devices, excessive fuel consumption, overheating of the coolant and equipment failure.
The formula for determining the power of the boiler:
Wcat = (S x Wud)/ten (kW) where
Wcat – boiler power, kW;
S – heated area, m2;
Wud – power density of the climate zone per 10 m2 floor space, kW.
Table 1. The value of specific power by climatic zones:
|Climate zone||Moscow region||Northern areas||Southern areas|
|Power density||1.2? 1.5||1.5? 2.0||0.7? 0.9|
Important! Simplified method for calculating power (1 kW per 10 m2 area) does not take into account the climatic conditions of the area, height, materials and the degree of insulation of the house.
Effective operation of autonomous heating is impossible without compliance with a set of measures:
- insulation of ceilings, floors, exterior walls, roofs, basements, attics, installation of double-glazed windows and modern door blocks;
- carrying out a preliminary heat engineering calculation (determination of heat losses through the building envelope);
- compatibility of heating equipment – design recommendations;
- high-quality installation of the system, compliance with the rules of commissioning and operation of equipment;
- timely prevention – flushing and hydraulic testing of the heating system at the end of the heating period;
- preliminary water treatment – filtration and softening of boiler water.
Water heating system is simple, reliable and economical: the boiler produces, and the water flow through the secondary circuit transfers thermal energy to the dwelling. The volume of water in the heating system is conventionally taken as 15 liters per 1 kilowatt of boiler power. The enlarged standards take into account the filling of the boiler and secondary circuits, the capacity of radiators, risers, wiring pipes, heat exchangers, hydraulic separators, distributor combs and heat storage tanks.
The natural transfer of thermal energy occurs according to the laws of gravity. Forced circulation of coolant makes the process directional, predictable and manageable.
Heating houses up to 100 square meters. m
Heating of houses of a small area does not require installation of pumping equipment – the movement of the coolant occurs in a natural way. The liquid, passing through the heat exchanger of the boiler, heats up. The density of the medium decreases, and the volume increases and pushes the flow from the boiler to the main riser. The heated water rises, enters the distribution line, then into the heating devices. After transferring heat to the radiator body, the coolant cools down, and its density increases. At the outlet of the heating devices, the cooled water enters the return line and moves towards the boiler.
The supply and collecting pipelines are laid with a slope in the direction of flow (supply line to the heating devices, return pipe to the boiler).
Heating houses over 100 square meters. m
Houses with an area of more than 100 m2, Equipped with a system of forced circulation of the coolant. The power of the boiler and the pump depends on the heat load of the room, the total heat loss, the number of heating circuits and appliances. Traditionally, pumps are installed on the bypass of the return line, through which the cooled coolant returns to the boiler. Additionally, they pressurize the long-distance hot water system and the independent low-temperature heating circuits of the underfloor heating.
Circulation pumps for heating are chosen as a compatible element of the system, taking into account the nominal capacity and head. The operational characteristics of the pump specified in the technical data sheet must correspond to the calculated values.
Calculation of pump performance:
G? Q / (? T x 1.16) (m / s, l / s, m3/ hour), where
G – circulation pump capacity, m3/hour;
Q – the maximum power of the boiler, according to the passport data, kW;
?T is the temperature difference in the supply and return pipes of the heating system, ° C;
1.16 – coefficient of specific density of water, Wh / kg ?.
Calculation of the pressure of the circulating pump:
H? (R x L x Z?) / 1000 (m) where
H – the pressure of the circulating pump, m;
L is the total length of the supply and return pipe, m;
R is the maximum value of resistance in straight sections (Pa / m, 0.015 pascal per 1 linear meter);
Z – product of safety factors for local resistance, Pa: resistance in ball valves, bends and fittings; internal resistance in chokes and thermostatic regulators; resistance in mixers and taps. If the heating system includes valves, fittings, thermostatic valves, mixers, then Z? = a x b x c.
Modern technologies allow you to automatically adjust the rotor speed. The pump responds independently to peak changes in operating load. Adapted models of autonomous heating heat generators are equipped with a circulation pump integrated into the boiler circuit.
The eco-friendly and non-volatile version of water heating from a wood-burning stove is successfully used by residents of some regions of Russia. The reasons for the organization of furnace heating of a private house without gas and electricity – the absence or distance of the pipeline, the high cost of connecting communications.
Heating furnaces made of brick are heavy, they are installed on a separate foundation. The furnace is laid out refractory bricks. Inside they install a welded coil of steel with a thickness of 3 × 5 mm, which is connected to the water heating circuit. Sometimes a boiler loop is built into the masonry array, shielding from the high temperature zone.
Dimensions, shape and position of the heat exchanger should ensure the required heating of the coolant. The coil, located in the body of the masonry, allows you to get at the output of heating, sufficient for the low-temperature contour of warm floors (30? 60 ° C). There are no general recommendations for the construction of brick ovens. Experienced stoves work on their own calculations and drawings, keeping the secrets of craftsmanship in the strictest confidence. The cost of services of professional stove-makers (ranging from 40 thousand rubles and above) depends on the region, materials and design of the hearth.
The advantage of stone wood-burning stoves heating: individual project selection and repair, available for self-fulfillment. The array and heat capacity of the material allows you to accumulate thermal energy. Radiation of heat from the surface of the masonry does not stop after the end of the burning of wood, which creates a comfortable environment in the house. Wood burning stoves are additionally used for cooking, water heating and household needs.
The lack of water heating from a brick kiln on the wood: a decrease in the speed of the coolant during cooling of the stone. Installing a circulation pump increases heating efficiency, but makes the system dependent on electricity supply.
Factory models of classic wood-fired boilers belong to the category of solid fuel. Non-volatile equipment made of cast iron or steel. Durable cast iron units consist of prefabricated sections, which allows the repair and replacement of elements. Steel models withstand sudden changes in pressure and temperature. The disadvantages of the classic solid fuel boilers: the need for frequent fuel loads and mechanical cleaning of the furnace, chimney, ashpit.
Pyrolysis (gas generator) units are distinguished by operating time on one tab up to 10 hours, efficiency 90%, complete combustion of fuel. However, the conditions of stable combustion depend on the quality of firewood (coal) and the completeness of the loading of the combustion chamber. Adjustment and automation in the process of pyrolysis is impossible, so the power of the unit changes in stages, from the beginning, the peak and the end of the combustion.
The device of solid fuel boilers long burning is fundamentally different from pyrolysis. Designs with a vertical firebox and metered air inflow increase the burning time.
The possibility of using any type of solid fuel and switching to an alternative method of heating increases the attractiveness of the combined models. Modification of the units allows, if necessary, to install gas burners and electric heaters in the furnace. The manufacturer’s recommendations, indicated in the boiler passport, facilitate the installation of the unit, the installation of the chimney and the choice of additional equipment.
Models of combined heating boilers (wood / electricity) are in particular demand among buyers. The price of units of the same power is presented for comparison in the overview table:
|Description of the unit (passport specifications)||power, kWt||Dimensions (LxWxH), mm||Price, rub|
|Solid fuel pyrolysis boiler Bourgeois-K (Standard – 10), floor:|
|Solid fuel boiler in the outdoor version Buderus Logano S111-2-12:|
|Solid fuel boiler long burning Zota Poplar M-14 (with the ability to complete a gas burner and electric heaters):|
Domestic developments have gained consumer recognition in the category of quality-price of solid fuel boilers for heating a private house. Reviews, which leave the owners of the equipment in independent forums, indicate the competitiveness of Russian brands.
According to statistics, 2/3 of autonomous heating systems are a variant of gas heating of a country house. Cheap fuel justifies the high cost of the units: the gas enters the furnace automatically, constant control over the combustion process is not needed. Gas heat generators are completed with a burner, an integrated circulating pump, an expansion tank, a heat exchanger, a security system and an automation group.
Consider the classification of gas fired boilers and give an example of calculating the gas consumption for heating a private house.
Gas boiler is chosen according to the power of the unit. The standard condition is 1 kW of boiler capacity per 10 square meters of space is observed if the structural elements of the building are insulated and the ceiling height does not exceed 3 meters. Dilapidated walling or installation of a heat exchanger for hot water is the reason for choosing a heat generator with a performance margin.
Important! The unit capacity stated in the data sheet corresponds to the standard pressure in the supply gas line (0.003 MPa low pressure). In practice, the gas pressure is lower than the agreed values, therefore, the boiler power may differ significantly from that indicated in the passport.
Steel single-circuit heating units with a copper heat exchanger used for heating small houses. Heating gas generators equipped with automatics are used for radiator heating and low-temperature contour of warm floors. For hot water, the system is supplemented with a boiler and a circulating pump.
Dual-gas boilers are used simultaneously for heating and hot water preparation. There are floor models of double-circuit gas boilers made of cast iron, with a built-in storage boiler. The wall version of lightweight construction, with a heating ring and instantaneous water heater, is made of steel.
Open fireboxes take the air for burning gas from the room in which the boiler is installed. The equipment should be located in a special combustion room equipped with fresh air ventilation and a vertical chimney.
Gas boilers with a closed combustion chamber are working due to forced air intake from the street. The associated removal of combustion products warms up a portion of fresh air and increases the efficiency of the heat generator.
The classic way to remove exhaust gases is through natural draft or forced exhaust through a chimney. The modern version is a coaxial hood in the type of pipe in the pipe. This exhaust system does not require the installation of a classic chimney. Combustion products are discharged through the inner tube. Fresh air enriched with oxygen is drawn into the gap between the inner and outer shell of the pipe. External weather conditions do not affect the air supply to the combustion chamber and exhaust gases.
Important! Gas fired boilers are classified as explosion and fire hazardous aggregates. The installation regulations of the generator are prescribed in the regulatory documents concerning individual boiler installations. Compliance with the rules requires personal safety considerations: with a lack of oxygen, natural gas does not burn completely. The resulting carbon mono oxide (CO ^) is colorless and odorless. The presence of 1% carbon monoxide in the air of the room is dangerous to human health and life. Fuel leakage and the formation of an explosive gas-air mixture can lead to tragic consequences.
Gas consumption for heating a house 100 m2
A preliminary calculation of gas consumption is carried out to determine the economic profitability of the generator and the feasibility of using other types of fuel. Estimated gas consumption can be found in the technical data sheet of the boiler. Manufacturers indicate the hourly need of the resource. The value is multiplied by 720 (the number of hours in a day and days in a month), then divided by 2 (the recommended power adjustment) and multiplied by 7 (the average heating period).
According to the theory, the economical operation of the heat generator makes it possible to generate 1 kW of thermal energy when burning 0.1 m3 gas. This means that by burning one cubic meter of gaseous fuel, you can heat a dwelling of 100 square meters for one hour. Daily gas consumption 24 m3.
The question of what kind of heating is better for private houses, each owner decides for himself. However, it must be remembered that the economic feasibility of new-fashioned tendencies is doubtful, and the repair of high-tech boilers in remote areas is problematic. The best option is a combination of units with different fuels.