This article we begin a series of articles devoted to the use of HVAC equipment for heating and domestic hot water (DHW) .
On our domestic market climate in the eyes of consumers conditioned firmly established reputation devices that buy solely for cooling the indoor air . The function of heating, and in rare cases it is regarded as more . However, around the world related to modern split- systems is quite another . In some countries , such as Britain, Norway, Sweden , Germany and others, the majority of purchases of air conditioners is made mainly due to the heating function . Modern split – systems operating in heat pump mode (Heat Pump), can work not only for heating the air in the room , but also used in the heating system for hot water .
In this article we will try to simple language accessible to the consumer in the form of talk about the use of air conditioners for heating . We will not go into technically sophisticated consumer jungle describe heat pumps , and in a simple manner try to convey to him the story about the pitfalls that exist in the field of application of air conditioners, as well as the principles of selection models. We hope that this article will be useful to buyers , and they will be happy with the choice that will make after reading this article .
Reversible operation mode
Basically, to get to work on the air conditioning heat is not very difficult – just change the direction of flow of the thermodynamic cycle . Conditioners that can run on both cold and heat , called reversible . AC working on heating , absorbs heat from the outside space: in this case the function outdoor and indoor as it reversed. Accordingly , heat is obtained not by direct conversion of electricity into heat , and due to the thermodynamic cycle . This method is economical conversion as per kilowatt of electricity consumed is produced by more than 3 kW of heat ( some manufacturers this figure has long passed the point of 4.5 kW of heat energy per 1 kW of electricity). This class of equipment in the world is called heat pumps (Heat pumps).
Reversible models of air conditioners, which in addition to the cooling function , capable of operating in the heating mode , have long ceased to be a rarity in the market. Moreover, now almost all models produced by manufacturers , are reversible . The difference in price of split systems , which can run on heating and air conditioning, which do not have such a function , has become so insignificant that many manufacturers are excluded from the production of so-called “cold model”.
Problems of air conditioners at subzero temperatures
1. Usually when the outdoor temperature is below -5 ° C , refrigerant R22, and -10 ° C, refrigerant R410a, the air conditioning is not recommended: the changing physical characteristics of refrigerant and compressor oil. At lower temperatures, the compressor oil ceases to be dissolved in the refrigerant , resulting in a so-called “dry” the start of the compressor , which can cause failure of the compressor at the start. But in the case where the compressor is broken up until the oil dissolved in the coolant , the wear of the compressor is increased , thereby reducing the life of the compressor .
2 . At negative temperatures frostbite occurs outdoor heat exchanger and then including air conditioning heat exchanger defrost mode . When you turn on the air conditioner starts defrosting the heat exchanger to raise the temperature of positive temperatures . Melting of ice occurs . The temperature of the water that falls into the sump of the outdoor unit is 0-1 ° C. Then the water that falls into the pan , naturally flows into the drainage holes . However, some of the water does not have time to drain from the drain pan and freeze it . This represents a threat to the normal functioning of the split system , as overgrown ice stops the operation of the fan , which usually leads to failure of the fan motor. The formation of ice in the tray of the outdoor unit also causes deformation of the bottom part of the exchanger (in some cases there is even a depressurization of the refrigerant heat exchanger and out into the atmosphere ) .
3 . Further problem is that when the temperature of air in the street begin to change the characteristics of the heating mode . Since the enthalpy of the air when the temperature begins to drop , the thermal energy from the air conditioner is becoming harder and harder to take . This leads to a drop in productivity and thus an increase in power consumption. In the HVAC industry all manufacturers made in the catalog data give power heating mode when the outside air temperature +7 ° C. When selecting a model should take into account this fact and require the supplier specifications conditioner is at the temperatures at which you want to operate the air conditioner .