Do you want to equip convection heating in the house, where an air-to-air heat pump is used to heat the coolant, which provides significant savings in heating costs? Agree that getting a full heating in a company with hot water is almost free - a very tempting event.
But you don’t know how to build such a system in order to heat rooms and get hot water for domestic needs in an alternative way?
We will help to deal with this issue - the article highlights the principle of operation and the design of the pump. The energy of such a system will have to be spent only on the operation of the compressor, and the bulk of the heat will be taken just from the street from the atmosphere, for which we do not require money.
The advantages of its implementation in the system and significant disadvantages are also considered. Special attention is paid to the selection and calculation of the pump.
And for lovers to do everything with their own hands, we offer to build such a pump on their own, using improvised materials. We provide photographic materials and video recommendations on the design and functioning of the heat air pump to help.
Air-to-air heat pump characteristic
Any heat pump refers to equipment from the field of alternative energy. He takes the thermal energy of the air masses on the street, from the surrounding space in the room, to warm it with residential and non-residential objects.
No combustible fuels are used.
Externally, the heat pump (TN) air-to-air is similar to an inverter air conditioner, a split system from an outdoor and indoor unit.
And according to the principle of action, it is more like a refrigerator, it only acts “vice versa”. But unlike both of them, this heat pump is capable of both cooling and heating the air masses in the house.
The heat pump takes low-grade heat energy from the atmosphere from the street and heats the room air with it to comfortable temperatures
Principle of operation and internal arrangement
A simple physical phenomenon of thermodynamics is the cornerstone of the operation of air-to-air heat pumps - a liquid cools the surface with which it is dispersed during evaporation. For example, steam above a mug of hot tea shows the same effect.
An ordinary refrigerator also works on this principle. Inside it are tubes through which the refrigerant circulates under high pressure. It takes heat from the inside of the freezer, slightly warming up at the same time.
Then the collected heat is transferred to the room air through a heat exchanger (grilles behind the refrigerator).
In winter, the air-to-air heat pump heats the room air, and in summer it can cool it
And so that after the refrigerant cools to operating temperatures, it is compressed in the compressor. Moreover, during the cycle of operation, the freon inside the compressor-condenser-evaporator system constantly changes from a gaseous state to a liquid state and back.
The air heat pump functions in exactly the same way. He only takes heat from the street, and not from a closed freezer. Even if it is frosty outside, there is still a lot of thermal energy in the atmosphere.
To produce heat, the heat pump only needs the energy spent on the compressor. The diagram shows in detail the process of heat transfer
The air-to-air heat pump consists of the following elements:
- compressor;
- Evaporator with forced air blower;
- expansion valve;
- copper pipes for pumping freon between the street and the house;
- a condenser with a fan for supplying heated air to the room.
The first three elements make up the external unit, and the last refers to the inside of the heat pump. Heat-insulated copper tubes are designed for continuous movement of the coolant between these modules of the split system.
The movement of freon in the heat pump occurs in a vicious circle, as a result of which it constantly contracts and expands
The algorithm of the air-to-air heat pump is as follows:
- The street air is drawn in by the fan into the outdoor unit and driven through the fins of the external evaporator. The freon circulating through the heat exchanger absorbs the thermal energy in it, turning into a gaseous state.
- Then the gas enters the condenser, where it is compressed. And then it is pumped through copper pipes to the indoor unit.
- In the condenser located in the house, the gas passes back into the liquid, transferring heat to the indoor air.
- Then the excess pressure is vented by means of an expansion valve, and the liquid freon is again sent to the primary evaporator.
The temperature of the freon entering the external unit is always lower than the ambient temperature. Therefore, it always takes heat from the atmosphere.
But the level of “cooling” of the coolant in the system is constant, and the outside temperature is constantly fluctuating. For this reason, in severe frosts, VT loses its effectiveness.
The cycle of movement of the heat carrier of the air-air heat pump: 1. it is compressed by the compressor, 2. condenses in the heat exchanger, while giving off heat, 3. enters the external heat exchanger in the form of liquid, 4. it evaporates there, capturing the thermal energy of the external medium during evaporation, 5 returns to the capacitor again
To increase the capacity of the heat pump, the surfaces of the condenser and evaporator are made as large as possible. And for uninterrupted operation in the winter, the outdoor heat exchanger is equipped with its own defrosting system.
Pros and cons of an air heat pump
Each technically complex system has its own advantages and disadvantages. Handouts are one thing, but in reality heat pump owners run the risk of encountering certain problems.
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Using the pump all year round
Air-to-air system mounted next to the house
Indoor air-to-air pump unit
Outdoor unit for a branched system
Air-to-air heating / cooling plants are beneficial for a number of reasons.
The main advantages include:
- Universality. Systems allow you to heat and cool rooms depending on the purpose of the room, needs and the climatic season.
- Environmental friendliness. They make it possible to completely abandon the burning of natural gas, coal, firewood, etc., clogging the natural environment with combustion products.
- Easy installation. It is not difficult to assemble a system of components of factory production. You can build your own heat pump from improvised means.
- Fire safety. The process of generating heat is not associated with the use of fuel. Even irregularities in the operation of the installation cannot cause fires.
- Profitability. Attracted by a high heat transfer coefficient at minimal cost (they produce 4–5 kW of heat for the consumed 1 kW of electricity). In addition, they quickly pay off.
- Affordable for the price. The cost of factory-made systems allows you to purchase a heat pump for almost everyone. Self-made installation will be almost free.
- Convenience of operation. The most technically sophisticated device in the system is a compressor, the maintenance of which is difficult not to cope. With a load typical of heat pumps, compressors rarely fail before the manufacturer's promised time.
To organize heating in one room, it is enough to install a split system by hanging an external module on the facade, and a convector on the internal wall.To heat several rooms will have to equip the distribution channels of heated air.
For every kilowatt of electricity consumed, the heat pump delivers up to five kilowatts of thermal energy
All control of the air-to-air heat pump is done by integrated automation. Particular attention will not be paid to the operation and configuration of this system. You will only need to clean the air filters regularly and sometimes change them.
Among the negative sides of heat pumps are the following:
- albeit a slight, but still noisy background;
- direct dependence of system efficiency on external temperature;
- increased power consumption during cold weather on the street;
- dust constantly hanging in the air due to continuous operation of the fan and air convection in the room;
- dependence on power supply (for uninterrupted operation, a generator is required).
At temperatures outside to -10 ° C everything works fine, the heat taken from the street is enough to create comfortable conditions in the house. But with further cooling, the efficiency of the pump sharply decreases.
If the cottage is built in an area with a cold climate and severe frosts in winter, then you can not do without an additional boiler or fireplace.
In a warm climate, an air heat pump can easily cope with the tasks of heating a private house, but in severe frosts an additional heat source will not hurt
Such systems are ideally suited for arranging air heating. Minimum energy consumption, installation effort and maintenance problems. But they can not heat the water. To do this, you will have to additionally install a boiler or connect to centralized networks.
Air-to-air heat pumps are the best way to heat buildings made of wood or SIW. Such buildings have low heat losses, the air heat pump capacities for their heating are in excess.
In summer, the air-to-air heat pump can be used to heat pool water
The main differences from the air conditioner
Externally, the air-to-air heat pump is similar to a domestic air conditioner. But it has its own distinctive design features and specifications.
The first device is used as the main source of heating, working year-round. And the second is more intended for cooling air in the summer heat.
The main function of the heat pump is heating. However, many models are also capable of cooling room air. But in this mode of operation, they are significantly inferior to the air conditioner in energy efficiency. This is rather an extreme case of their use.
In appearance, air conditioning and air VT are similar, but have completely different purposes and operational characteristics.
On the other hand, many inverter air conditioners can heat indoor air. But at the same time they consume much more heat pumps. Each device has its own purpose.
The use of air-to-air heaters is primarily a switch to renewable energy sources.
These systems are economically viable, despite large initial investments. Reducing heating bills pays off all upfront costs.
Selection and calculation of the heat pump
An air-to-air heat pump will be effective only if it is correctly selected. It is necessary to calculate its power in advance, depending on the quadrature of the house. And only then look at the prices of different manufacturers.
In the calculations, the coefficient of energy efficiency of the COP is used (the ratio of the power of the VT to the energy consumed).
Under “greenhouse conditions” it often reaches 4–5 points, and the most modern models up to 7–8. However, when the outdoor temperature drops to -15–20 ° С, this indicator drops sharply to just two.
The heat pump gives optimal productivity for heating at outdoor temperatures of -10 ... + 10 degrees Celsius, so it takes up to ¾ of thermal energy from the street
When calculating air heating, it is necessary to take into account:
- thermal insulation and insolation of rooms;
- area of rooms;
- number of residents in the cottage;
- general climatic conditions of the area where the house stands.
For most homes, about ten kW of heat pump power is needed for every ten square meters. But everything here is rather arbitrary. If the ceilings above 2.7 m or the walls and windows are poorly insulated, then more heat will be required.
There are many manufacturers of air-to-air heat pumps in Asia and Europe.
Good reviews have systems from Daikin, Dimplex, Hitachi, Vaillant, Mitsubishi, Fujitsu, Carrier, Aertec, Panasonic and Toshiba. Almost all of their models are adapted to domestic operating conditions and have proven themselves well.
Even with voltage drops, they do not break, continuing to work properly after turning on the electricity.
The price of running air heat pumps varies in the range from 90 to 450 thousand rubles. Here a lot depends not only on the capacity of the unit, but also on additional functionality and the country of manufacture.
Separate models complement:
• filters for cleaning and disinfecting air;
• backup heaters;
• electric generators;
• GSM modules to control the system;
• ionizers and ozonizers.
Practice shows that in frosts below -15 ° C in rooms heated only by a heat air pump it becomes cool. And without an additional heater, the comfort in the rooms frankly does not smell.
However, in southern regions where such frosts are rare, VT is quite effective and justifies the money spent more than due to energy savings.
Homemade from an old refrigerator
It is quite difficult to assemble an air-to-air heat pump from separate compressors and condensers without any specialized engineering knowledge. But for a small room or greenhouse, you can use the old refrigerator.
The simplest air heat pump can be made from the refrigerator by stretching an air duct into it from the street and hanging the fan on the rear grill of the heat exchanger
To do this, make two holes in the front door of the refrigerator. Through the first, street air will enter the freezer, and through the second lower one it will be taken back to the street.
At the same time, during the passage through the inner chamber, it will give part of the heat present in it to freon.
You can also simply refrigerate the machine into the wall with an open door to the outside, and a heat exchanger at the back to the room. But it should be borne in mind that the power of such a heater will be small, and it consumes a lot of electricity.
Indoor air is heated from the heat exchanger at the back of the refrigerator. However, such a heat pump can only work at outdoor temperatures of at least plus five Celsius.
This household appliance is designed for indoor use only.
In a large cottage, the air heating system will have to be supplemented with air ducts that distribute warm air evenly throughout the premises
Installation of an air-to-air heat pump is extremely simple. It is necessary to install the external and internal blocks, and then connect them together by a circuit with a coolant.
The first part of the system is installed on the street: directly on the facade, on the roof or next to the building. The second in the house can be placed on the ceiling or wall.
It is recommended to mount the outdoor unit a few meters from the entrance to the cottage and away from the windows, do not forget about the noise made by the fan.
And the inner one is set so that the stream of warm air from it spreads evenly throughout the room.
If you plan to heat a house with several rooms on different floors with an air-to-air heat pump, you will have to equip the ventilation duct system with forced discharge.
In this case, it is better to order the project from a competent engineer, otherwise the TN power may not be enough for all rooms.
The meter and protective device must withstand the peak loads created by the heat pump. With a sharp cooling outside the window, the compressor begins to consume electricity many times more than usual.
It is best for such an air heater to lay a separate supply line from the distribution panel.
Particular attention should be paid to the installation of tubes for freon. Even the smallest shavings inside can damage compressor equipment.
Here you can’t do without the skills of brazing copper. Refueling refrigerant generally should be entrusted to a professional in order to avoid later problems with its leaks.
Step-by-step instructions for making a heat pump from a refrigerator are described in this article.
The principle of operation of the thermal split system "air-air":
Air heat pump in the heating system of a two-story house:
Air conditioning inverter or heat air pump - which is better?
Air-to-air heat pumps are highly efficient devices. They are easy to maintain, easy to operate and economical.
On sale now is a huge assortment of similar systems, for any home you can choose a heating installation. It is only necessary to correctly calculate its power, then it will effectively serve for many years.
What do you think about the efficiency and feasibility of using air-to-air heat pumps? Share your opinion, leave feedback on the use of units and ask questions. The comment form is located below.