The traditional water system transfers thermal energy to the premises through water or non-freezing liquid (antifreeze). But there is another solution - purely air heating at home, in which the air of the rooms is heated directly, without hydraulics and radiators. Since this topic is being actively promoted by interested manufacturers of heating equipment, we decided to find out how much better (or worse) air heating than classical and whether it can be mounted with our own hands.
Air heating options
So, our task is to heat the air masses and submit to the premises of a country cottage or apartment. How can you arrange air heating:
- From the fireplace, wood burning stove.
- Use VRF-systems on Freon. Simply put, inverter air conditioners, air heat pumps.
- Install the combined air conditioning system boiler + chiller + fan coil units.
- To organize centralized air heating (abbreviated - IN), combined with ventilation of a private house. To use a heat source, use an electric air heater or a gas air-heating stove.
Reference. The latter option is often implemented in American and Canadian cottages built using frame technology. The heater is a gas furnace.
For heating / cooling of production halls of a large volume, a slightly different scheme is implemented. In the premises 2 networks of ducts were built - supply and exhaust. Both converge to a ventilation unit - a central air conditioner, consisting of such units:
- 2-3 step filters clean the air masses before being fed into the building and released to the outside;
- heat exchanger-air heater No. 1 heats the stream with the help of hot water from the boiler room;
- heat exchanger No. 2 serves to cool the air, works in tandem with the chiller;
- lamellar cross (or rotational) recuperator takes the heat of the exhaust stream and gives it to the supply, saving 50 ... 80% of energy;
- humidification unit;
- centrifugal fans make the flows move through the sections of the central air conditioner and further along the air ducts.
Why did we describe the design of an industrial air conditioner? So that you immediately understand: the device of complete air heating + ventilation + cooling is a difficult and expensive task. But, being the owner of a country house, you can consider all methods of heating, choose the simplest and cheapest, or return to the water scheme - underfloor heating, radiators.
How to organize stove heating
An important advantage of any stove: it simultaneously heats the air and surrounding surfaces with intense infrared radiation. Batteries and coolant pipes are not needed.
Clarification. Stoves or fireplace inserts with a water circuit can be used for heating 2-3 small rooms. The coil is connected to a gravity or closed system with a pump.
How to use the stove for purely air heating:
- On 1 room it is enough to install a cast-iron or steel potbelly stove.
- To heat 2-3 rooms with a total area of up to 40 m², lay a brick stove of a suitable design in the space between the rooms.
- It is not easy to build a stove in an old house. If there are no high aesthetic requirements, we put a potbelly stove, attach convection covers to the furnace and connect air ducts.
Option number 3 involves laying air ducts in neighboring rooms and installing duct fans that can withstand the temperature of the transported medium 100-150 ° C.The air can move through the pipes and independently, but too slowly, and the ventilation duct should go with a slope up. How such an air heating system works, see the video below.
The first two options are well known, but not always applicable:
- it is generally unrealistic to put a stove in an apartment;
- even a large Russian stove is not able to cover an area of more than 50 squares (on one floor), so it is suitable for heating a summer house or a small house;
- foundation plus a brick stove-fireplace is being erected at the stage of construction or overhaul of a building;
- metal potbelly stove takes place and is dangerous for young children (in terms of burns).
You can install an iron stove with your own hands - this is a tangible plus. But it will also have to be drowned, hence a lot of inconvenience arises: frequent downloads, the smell of firewood and smoke in living rooms, dust. The author of the video acted reasonably by placing a potbelly stove in a separate furnace.
We do not recommend repeating one thing for the home master - to install air ducts made of aluminum corrugations. Such pipes create high aerodynamic drag, greatly slow down the flow. It is better to use galvanized boxes.
Preliminary conclusion. Solid fuel stoves are a budget option for air heating with its own advantages and disadvantages. Suitable for small buildings - country houses, garages, greenhouses.
The use of air conditioners and heat pumps
As you know, modern split systems are able to function in heating mode, spending three times less electricity than a conventional electric boiler of the same power. Hence, a completely working solution is to buy and put an inverter air conditioner in each room.
Reference. Why exactly the inverter? The compressor in such "splits" does not stop, respectively, does not freeze in the cold. The air conditioner successfully heats the air to -5 ° C on the street, then the efficiency decreases noticeably.
The advantages of this scheme are obvious:
- lack of batteries, pipes, boilers and other heating equipment;
- relative ease of installation;
- aesthetic appearance of the indoor unit;
- summer cooling mode;
- the ability to install in apartments.
Air conditioning heating is viable in the southern regions, where temperatures rarely drop below -15 ° C. To the north, “splits” are used only in the transitional period - in spring and autumn.
The remaining disadvantages of heating with a split system:
- Air conditioning will have to be installed in all rooms, which is unacceptable for cottages 2-3 floors. A multi-split VRF system will cost more than the same number of single coolers / heaters.
- The device "knows how" to clean, dry and change the temperature of the air stream. Rare models are designed to mix outdoor air. So you have to do a separate ventilation.
- When the external air conditioner unit is operating, a clear fan noise and a humming compressor are heard from behind the wall.
The problem of efficiency at low temperatures is solved by the “air vent” heat pump, whose operability is maintained up to -30 degrees below zero. The design and principle of operation are identical to the split system, the differences are large sizes and price. If the outdoor unit is installed on the ground and carried 2-3 meters from the building, the noise of the unit will become inaudible.
A brief conclusion. VRF systems are good for apartments and small houses in the southern areas. Heat pumps can be installed in northern latitudes, but the cost of equipment plays a role here. If desired, the air conditioner can be installed independently.
Combined multi-zone systems
In this case, the coolant is still used, so the system is called combined. How does this equipment work:
- In each room there is an air heating / cooling unit - a four-pipe fan coil that looks like an indoor unit of an air conditioner.
- In one pair of pipes, the coolant from the boiler is supplied to the units.Hot water passes through a heat exchanger blown by a fan, due to which the room air is heated.
- When it is necessary to switch to cooling, the automation switches the fan coil to a second pair of pipes supplying cold water from the chiller.
- Users in rooms can set different air temperatures, but you cannot turn on cooling and heating at the same time. Hence the second name of the air conditioning system - multi-zone.
Note. Chiller is a type of refrigeration machine designed to cool a liquid. It is usually located on the street under a canopy or in an open area (depending on the design).
Inside the building, various fan coil units are used - wall, duct, floor, ceiling. It all depends on the wishes of the homeowner and the requirements for aesthetics. Duct type units can be built into the ventilation ducts for heating / cooling the supply air.
Advantages of multi-zone air systems:
- applicable in buildings with a large area with the number of rooms of 20 or more - administrative and residential buildings, warehouses and so on;
- can work together with forced ventilation of the cottage;
- any heat generator is used for air heating - a solid fuel boiler, gas, electricity, diesel fuel;
- pipes with a coolant (coolant) take up little space, air units are easily integrated into the ceiling, suspended on the wall or hidden behind the lining;
- closed terraces with stained-glass windows throughout the wall are heated by floor convectors or wall-mounted fan coil units;
- the ability to adjust the temperature in individual rooms, remote control.
We believe that the boiler + fan coil + chiller circuit is the most versatile, successful in terms of aesthetics and operation. Of course, you can’t do such air heating yourself, this is a minus. It is necessary to make calculations, select equipment, install, adjust ... without knowledge of the basics, it is extremely difficult to carry out these works.
We list other negative points:
- high price of air conditioning;
- the boiler and chiller are fairly large-sized devices, covering 2–3 m² of area;
- the operation of the system depends entirely on electricity; when the light is turned off, the heat supply will stop.
Conclusion. A multi-zone combination scheme is the best way to air-heat a home. But implementation will require significant investment.
Combined heating with ventilation
This is a classic way of heating buildings with air, used in enterprises since the last century. Subsequently, manufacturers began to produce small-sized analogues of industrial ventilation units installed in private homes. Thanks to less stringent requirements for air purity, the processing scheme has also been simplified.
Let’s explain the principle of operation of the “ventilation + heating” system step by step:
- The heat source is a stove, usually a gas stove. A burner, an air heat exchanger, a fan and an electronic control unit are installed inside.
- From the furnace, the first network of ducts disperses, distributing the heated air into the rooms. With the help of diffusers, gratings and other supply devices, jets are fed into the rooms (usually in the upper zone).
- The second network of channels collects contaminated / cooled air from the lower zone of the rooms into a common collector connected to the bottom of the furnace.
- After passing through the collector, the exhaust air masses are cleaned in a mesh or mesh filter, then they are sent to a heat exchanger, where they are heated by a burner.
- Electronics monitors the safe operation of the gas air heater, maintains the outlet temperature, and signals the pollution of the filters.
Addition. Since the heater dries the air, an automatic humidifier with an electronic hygrometer is usually placed on the supply channel. The latter is located on the return air duct to measure the humidity of the flow.
Air-heating stove - the unit is quite noisy, so it is placed in a separate room. The combustion products are removed through a conventional or coaxial chimney (depending on the design of the heater). Galvanized steel ducts are laid in several ways:
- on the basement or ground floor;
- hide in floors and wooden floors;
- in the attic;
- vertical channels run along the walls and are sewn up with facing materials.
The air temperature at the feed reaches 40 ... 45 ° C, the speed of movement along the ventilation channels is 4-5 m / s. You can’t do it faster, additional noise will appear. In this situation, the diameter of the main collector reaches 300 mm, we took a typical flow rate of 1000 m³ / h, although it happens more.
A logical question: why heat the air masses to 40 ° C, if the house has enough 22 degrees? We answer: the heating system must compensate for 2 types of heat loss - through building structures and energy consumption for heating the inflow, since ventilation is needed in any case. Accordingly, we bring the air to a temperature of 20-24 ° C (compensate for the loss of the house), then overheat to 40 ... 45 ° C.
Conclusion The “ventilation + heating” scheme is the most cumbersome and expensive. The building must be prepared in advance - even at the design stage, otherwise the ducts will go right through the rooms. Efficiency greatly depends on the ventilation method of the building, which we will discuss later.
3 ways of air exchange
So we smoothly approached the air exchange schemes, of which there are three:
- The method described above is called full recirculation. The same air is driven through an oven or air conditioner, there is no update or is organized by other means. For example, the inflow is provided by wall valves, natural exhaust by vertical shafts inside the walls.
- With partial recirculation, the internal air is diluted with an influx of 30–50% of the total volume. As many polluted gases are thrown out. Natural ventilation is excluded, the system with mechanical motivation is engaged in air exchange, you cannot adjust the proportions in another way.
- Forward flow. All supply air is taken from the street, warmed up and sent to the premises. The exhaust system completely throws out contaminated air masses to the outside.
The first type of air exchange works with air heating with a wood stove, air conditioning and fan coil units. The method allows you to save energy, but the quality of the air remains doubtful, because it depends on the operation of natural ventilation.
The second option is a compromise between a clean home atmosphere and energy saving. We partially refresh the indoor microclimate, but at the same time we lose heat along with the air that is removed.
The third scheme gives us completely fresh air, but makes us spend maximum fuel on heating the inflow. In order not to throw heat out into the street, recuperators (utilizers) were invented - devices that take away the heat of the exhaust jet and give it to the inflow. Depending on the environmental conditions and the design of the utilizer, 50 ... 80% of the heat remains in the house, the heater consumes less energy.
Ventilation combined with air heating operates according to one of the last two schemes - partial recirculation or co-current with heat recovery. The last option is the most expensive, because in addition to the network of channels and the air heater, you need to purchase a heat exchanger-heat exchanger.
Which heating is better - air or water
The main argument in favor of the air heating option is the lack of radiators under the windows, pipe wiring and, in general, an intermediary in the form of a coolant. But even this statement does not hold water - water heated floors are also completely hidden, and the mediator is still present - the air itself.
Clarification. When heating with split-systems or heat pumps, freon acts as an intermediary, changing the state of aggregation.Heat to the fan coil is delivered by water or antifreeze, in other cases air masses carry energy.
We offer to compare water heating with air heating, based on advertising statements:
- The VO system has a higher efficiency. This is not true, the efficiency is the same, provided that in both cases heat generators based on the same fuel are used. The exception is air conditioners that consume 300 watts of electricity to supply 1 kW of heat.
- IN can be turned off in the middle of winter, nothing will freeze, pipes will not burst. This is true, but the radiator network, filled with antifreeze, also does not suffer from frost.
- Low cost of operating VO. The statement is true of stoves, air conditioners, fan coil units, and water systems. When heating with ventilation, you will have to clean the hidden air ducts from dust and bacteria. The operation is performed by specialized equipment.
- For air heating, you do not have to buy expensive shutoff valves, pipelines, batteries, combs. True, galvanized ventilation ducts are cheaper than water network equipment. But air ducts of Ø300 mm (equivalent to a square of 200 x 350 mm) must be laid somewhere, sewn up. The cost of installation will be considerable.
- VO heats rooms faster. Wrong, VO quickly heats the air, surrounding objects remain cold. Both systems will take the same amount of time to fully warm up.
- Together with air systems, additional equipment for cleaning, humidification, and ionization is used. Air quality is improving. That's right, underfloor heating or a radiator network does not clean up the home atmosphere.
The remaining arguments are very unconvincing. Example: by air, you can heat a room of any size on any floor. It is not clear what makes it difficult to lay 2 pipes on the 20th floor, to put batteries or fan coil units there. Instead, it is proposed to pull a hefty duct there.
Well-known expert Viktor Sukhorukov will explain all the pros and cons in detail in his video:
Final conclusions
This is not to say that air heating outperforms water heating in all respects. On the contrary, by the most important criterion for the user - the price - air systems are clearly losing. The cheapest method is heating with a wood stove, but its scope is limited. Only air conditioners are available in the apartment, sometimes fan coils. The most universal and reliable option for a private house is water heating, air heating is done in exceptional cases.