Is it possible to use an air conditioner for heating in frosty conditions and how to prepare it for this work?
The cold weather is coming, but you haven’t decided how to heat your home yet? Using an air conditioner for these purposes is very economical and tempting, but you don’t want to risk its performance, right? We will help you figure out whether it is possible to use an air conditioner for heating in frosty conditions, why and in what cases this can be dangerous for the equipment.
We will also tell you what to do so that you can use the air conditioner longer, at lower temperatures. Let's look at how practical and effective this application is. For complete clarity, we will show all the important points in photos and diagrams, and at the end of the article you will find educational videos on the topic.
The content of the article:
Why does the split system heat up?
To understand what can go wrong when you turn on the air conditioner in cold weather, you first need to understand what happens during normal operation of the heating system.
Unlike portable heaters of any type, a split system does not produce heat from the energy consumed, but only transports it from the street to the house or vice versa, depending on the mode. Does it sound unrealistic to take heat outside when the temperature is below zero? This is only at first glance.
The main components of any split system are a compressor, a radiator with a fan in each unit and a freon pipeline connecting them.The refrigerant is the main magician in this kit: it is thanks to its physical properties that it becomes possible to obtain heat in the cold and coolness in the heat.
The path of freon in air conditioners used in winter for heating at low temperatures looks like this:
- Cooled liquid refrigerant is supplied from the radiator of the indoor unit.
- Getting into the outdoor unit, it heats up and evaporates, because the boiling point of the refrigerant is -40 or -510C, and it’s warmer outside even in winter. After passing through the street radiator, the temperature of the freon rises, that is, it receives thermal energy.
- The resulting energy is low-potential and therefore cannot be immediately transferred to the air in the room. The compressor compresses the refrigerant gas and its temperature rises to 70 - 900C. In this state, freon is supplied to the indoor unit.
- Passing through the radiator of the indoor unit, blown by a fan, the refrigerant gives off heat to the room air, and itself cools and condenses into liquid. The circle is closed, everything is repeated from the beginning.
Thanks to this principle of operation, split systems are also classified as heat pumps, because they transport and pump heat from the street to the room or vice versa in the same way.
To operate, electricity is needed for the pump itself - the compressor, as well as two fans.Together they consume 3–7 times less energy than the system produces, which means that heating with an air conditioner is 3–7 times more economical than with an electric and gas convector, infrared stove or other heater.
Why is frost dangerous for an air conditioner?
The operating principle of an air conditioner is quite simple, but changing conditions at any stage can lead to serious damage.
Firstly, starting a cold compressor is dangerous. The oil in it thickens at low temperatures, and therefore the unit operates under increased load.
In addition, without lubrication, the friction of metal parts produces chips that clog and damage the system. Therefore, even a new compressor installed to replace a broken one can quickly fail even with correct operation.
Secondly, the freon in the external radiator may not have time to evaporate. The activity of heat exchange depends on the temperature difference. Therefore, with a slight plus on the street, freon, warming up from -400C, will absorb a lot of thermal energy.
If it's -30 outside0C, then the refrigerant may not have time to warm up even to the boiling point. The result is liquid freon entering the compressor and its inevitable breakdown due to water hammer.
The third danger is condensate freezing and icing..
An ice shell on the outdoor unit interferes with heat transfer and can interfere with the fan, which increases the load on all parts of the system. Automatic defrosting is designed to solve this problem, but the water draining from a heated radiator often immediately freezes in the pan.When the ice layer reaches a certain thickness, the fan blades freeze into it, and the air conditioner stops working.
Condensation in the drain pipe can also freeze at the point of exit to the street - if the air conditioner is working on cooling. This may be necessary in winter in server rooms or in the defrosting mode mentioned above. Such an ice plug prevents further drainage of condensate, and it begins to ooze down the wall, provokes the development of mold in the indoor unit, and can damage it.
Even cooling work in winter can cause problems. In this case, the air conditioner takes too much cold from the street, and the condensation on the indoor unit turns into frost and ice. Naturally, this is also detrimental to the equipment. In addition, the problem of cold start of the compressor remains relevant.
What kind of air conditioners can be used for heating?
When buying a split system, you should look for the word “reversible” in the description: it indicates the ability of the device to change the direction of freon flow and work for heating.
After the problems described, you may get the impression that the heating function in air conditioners is useless and dangerous for the device, but this is not the case. Split system Although it won’t save you in severe frosts, it will help create a comfortable microclimate in the off-season, when the central heating is turned off and it’s cold outside, or in a temperate climate.
The lower temperature limit at which the split system can be turned on for heating depends on the model - it is indicated in the instructions.
There are certain patterns in the distribution of these temperatures:
- Air conditioners with linear control type can usually only be turned on down to -50C, since the compressor is constantly switched off and has time to cool down before restarting.
- Inverter models usually work until -150C, but some specialized devices are effective down to -20 and even -300WITH.
- It is sometimes possible to expand the range of operating temperatures declared by the manufacturer by installing a winter kit - we’ll talk about this in more detail later.
- Monoblock air conditioners with a heating function do not depend on the outside temperature, but they are no different in terms of efficiency. In winter they work like regular convector, with an efficiency slightly less than 1.
- Systems with R22 refrigerant are less efficient and resistant to low temperatures than those filled with R410A or R32 freon.
It is worth noting that even those models that operate smoothly at low temperatures significantly reduce the efficiency and economy of heating when it gets cold outside.
Given operating temperature limitations and inconsistent performance, air conditioning cannot be the primary heating appliance for homes in northern regions.
Differences in the design of frost-resistant air conditioners
Why can one air conditioner be turned on at 30 degrees below zero, while it is undesirable to start others at -5?0WITH? The answer is simple: structural features and configuration. The cost of a split system is not always directly proportional to its capabilities, and therefore it is useful to know what effective design solutions exist.
To understand whether it is possible to turn on a particular air conditioner for heating in winter, or whether this is dangerous for the device, pay attention to such details.
Firstly, a low temperature kit should be built in from the factory to prevent cold starts of the compressor and condensate freezing.
As we have already mentioned, inverter models are preferable in winter, since their compressor does not stop when the set temperature in the room is reached, but only slows down. This means that it will not cool down every time and start up with an overload, and it is also more profitable in terms of energy consumption.
The heat exchanger of the outdoor unit can be enlarged so that the freon inside has time to completely evaporate and absorb maximum heat from the air before entering the compressor.
There are also double-circuit heat exchangers in which the performance is regulated by connecting an additional freon circulation circuit. The external unit and heat exchanger may include additional casings and heat accumulators to use the energy generated by the operating equipment.
A high-power compressor compresses the gas more strongly, heating it to higher temperatures. In industrial models, there are also scroll compressors that are not afraid of the ingress of liquid freon.
The refrigerant itself may have different properties. Cheap and abundant R-22 evaporates at -400C, while being able to absorb heat of 233 kJ/kg. For comparison, the newest R-32 evaporates at -51.70C, and can retain heat up to 390 kJ/kg.
This means that under the same conditions, the second one will heat up faster and more efficiently in the heat exchanger, and air conditioner or split system will operate with less energy consumption and higher efficiency.
The type of oil that lubricates the compressor also depends on the type of refrigerant. R-22 works with mineral oil, maintaining an acceptable viscosity down to -50C, and R410A and R32 – with synthetic, resistant to -70S. It would seem that the difference is small, but in combination with other factors it is significant.
The more of the listed upgrades the air conditioner has, the lower the temperature it can operate at. However, for many inverter models You may not even know the maximum permissible temperature: the electronic control simply will not start the system if it is too cold outside.
Winter air conditioner kit
Recently, more and more often you can find proposals for equipping an air conditioner with a winter kit. Sellers of this equipment assure that its installation will make the air conditioner an effective heater throughout the winter, even in frosty weather. Whether this is so - we will figure it out.
Components of a winter work kit
A low-temperature kit, as a rule, includes 3 components: a heating pan, a compressor crankcase and a fan speed controller. Sometimes there is also a temperature sensor and a control board - separate for each component or common to all.
Heating the pan is necessary to prevent the condensate draining from the radiator from freezing when the defrost mode is turned on.
The crankcase heater is a wire or plate that surrounds the compressor in the place where oil accumulates.
It is advisable to turn on the compressor heating before starting the air conditioner so that the oil has time to warm up. In practice, heating often occurs either only during operation or only during idle time. Only the second option will ensure safety for the compressor, but it is less profitable due to increased energy consumption.
Adjusting the fan speed determines the activity of heat exchange between freon and the external environment: the stronger the air flow, the more heat is transferred. When working for heating, this is not critically important, because maximum heat transfer is needed, and high fan speed is set from the factory.
It’s another matter if the air conditioner works for cooling at temperatures below +14 - +180permitted by the manufacturer. Then the freon can give off too much heat, and the indoor unit will begin to freeze: it will become covered with frost and ice, and the condensate will freeze. To prevent this from happening, the fan is slowed down.
Is it advisable to install a winter kit?
After installing a low-temperature kit, the owner may have a question: is it now possible to heat the room with an air conditioner at low outside temperatures? The answer is yes, you can, it is now safe for the air conditioner. The exception is unqualified installation or home-made equipment.
Is it effective? Air conditioning heating is valued for its efficiency: its efficiency can reach 3 – 5 and even 7, depending on the model. This is achieved by the fact that the split system is the only heater that does not produce heat. The compressor and fans require much less energy to operate than the system can move into the home.
The declared efficiency, or, as manufacturers write, COP, is relevant when operating for heating at +70 on the street. As it gets colder, the temperature difference between air and freon decreases, which means heat exchange worsens and the efficiency of the air conditioner decreases.
At temperatures below -150With the efficiency of the air conditioner reduced to approximately 1%, that is, for every kilowatt of electricity consumed, only 1 kW of heat can be obtained. Conventional convectors or infrared heaters, which are cheaper and do not depend on the outside temperature, also have such indicators.
Of course, these calculations are approximate; the result greatly depends on the model of the air conditioner, the low-temperature set, and even the connection diagram of the second one. But the fact is that the lower the temperature outside, the less effective and economical heating with a split system is.
Considering that the cost of a good winter kit for turning on the air conditioner heating with installation it can amount to 40 - 150% of the cost of the air conditioner, and it will help to work effectively only up to -150C, the feasibility of the purchase is highly controversial.
It's another matter if you need to cool the room in winter. For example, for a room with equipment.Then the lower limit of permissible temperatures drops from +16 declared by the manufacturer to severe frosts, and the efficiency of the air conditioner will not decrease.
Installation and connection of the winter kit
As we already mentioned, professional installation of a low-temperature kit is not cheap. Not every owner of a split system is ready to pay 5,000 rubles or more for the opportunity to turn on air conditioner for heating at a temperature 10 - 15 degrees lower than stated. If you're not prepared for that kind of expense, you might be interested in installing a winter kit yourself.
Let us remind you that to operate in winter, the air conditioner requires heating of the sump, the compressor crankcase and the RDK unit - a condensation pressure regulator that controls the fan speed. You can buy a ready-made kit and install it yourself.
Then you will be freed from the difficulties of choosing and searching for components, and will also save money on installation, but you will probably lose the warranty on the split system. Naturally, self-installation means additional hassle.
The most economical option is to buy 2 pieces heating cable, better than self-regulating, and connect them yourself. Controlling the fan speed when working for heating can be neglected; we explained why above.
To heat the tray, you will need a piece of heating cable about 3 m long. They lay it around the radiator both from the outside and from the inside, as well as along the entire tray in a snake.You can connect the power supply to the outdoor unit, like the factory heating, to the main phase - then the cable will always heat as long as the air conditioner is plugged in, even when idle.
Alternative options are to bring a separate cable with a plug to the outlet and turn it on manually, connect it to the network through a thermostat on the street or through a timer.
To warm up the oil in the compressor, wrap a piece of heating cable around it at the bottom. The electrical connection is carried out together with the heating of the pan.
If you purchased an RDK, you need to find free space for it in the control compartment, above compressor, and secure it with self-tapping screws. The electrical connection differs for different models and is always described in detail in the instructions. For correct operation, the sensor included in the kit is attached to the middle loop of the radiator, coated with thermal paste, and wrapped with heat-insulating material.
Conclusions and useful video on the topic
Some practical aspects are difficult to fully imagine from a text description, so we suggest you see and evaluate everything with your own eyes.
You can watch how to install the winter kit in this video:
What can happen to the air conditioner when operating without a winter kit is shown here:
The experience of heating a house only with air conditioners is described in detail here:
To summarize, we say that most air conditioners are designed to heat the room only in the off-season, before turning on the main heating. Even those models that are capable of operating at -300They are unlikely to be able to provide enough heat in such frost. However, if in your region the temperature rarely drops below -150Since, then heating with a split system is a very profitable and successful solution.
Do you already have a split system installed? Do you use it in cold weather? Did you need to install a low temperature kit? Share your experience, additions and amendments to the article in the comments.
