Heat Pump Systems
For climates with moderate heating and cooling needs, heat pumps offer an energy-efficient alternative to furnaces and air conditioners. Like your refrigerator, heat pumps use electricity to move heat from a cool space into a warm, making the cool space cooler and the warm space warmer. During the heating season, heat pumps move heat from the cool outdoors into your warm house; during the cooling season, heat pumps move heat from your cool house into the warm outdoors. Because they move heat rather than generate heat, heat pumps can provide up to 4 times the amount of energy they consume.
The most common type of heat pump is the air-source heat pump, which transfers heat between your house and the outside air. If you heat with electricity, a heat pump can trim the amount of electricity you use for heating by as much as 30%–40%. High-efficiency heat pumps also dehumidify better than standard central air conditioners, resulting in less energy usage and more cooling comfort in summer months. However, the efficiency of most air-source heat pumps as a heat source drops dramatically at low temperatures, generally making them unsuitable for cold climates, although there are systems that can overcome that problem.
For homes without ducts, air-source heat pumps are also available in a ductless version called a mini-split heat pump. In addition, a special type of air-source heat pump called a "reverse cycle chiller" generates hot and cold water rather than air, allowing it to be used with radiant floor heating systems in heating mode.
Higher efficiencies are achieved with geothermal (ground-source or water-source) heat pumps, which transfer heat between your house and the ground or a nearby water source. Although they cost more to install, geothermal heat pumps have low operating costs because they take advantage of relatively constant ground or water temperatures. However, the installation depends on the size of your lot, the subsoil and landscape. Ground-source or water-source heat pumps can be used in more extreme climatic conditions than air-source heat pumps, and customer satisfaction with the systems is very high.
A new type of heat pump for residential systems is the absorption heat pump, also called a gas-fired heat pump. Absorption heat pumps use heat as their energy source, and can be driven with a wide variety of heat sources.

Heat pumps become a more and more attractive heating device, as costs for oil and gas fuel constantly rise. Heat pumps use environmental (solar) heat stored in the ground, ground water or air. As ground water as heat source is not available at all locations or may be costly to provide, air is available at any location and is therefore an attractive versatile heat source. The following paper describes the advantages in using air as a heat source for heat pumps, and presents the new generation of air source heat pumps that are due to high flow temperatures suitable for the retrofit market.

2. THE UTILIZATION OF AMBIENT HEAT
Ambient heat is a 100 % renewable energy source that is available anywhere by using heat pump technology. The utilization of this technology is economically, sustainable and without harmful emissions on site. This is of the greatest advantage, both for environmental and for economical reasons. Ambient heat is the ever present energy stored in ground water, the ground itself and in the air. Ambient heat is the result of natural processes.

Heat pump technology is mature and has a significant contribution potential towards energy savings and climate protection goals. Therefore heat pumps – and of course also air source heat pumps are part of the EU Directive on the promotion of the use of energy from renewable sources (RES Directive).

Heat pumps are one of the few technologies that can cover the entire heating, cooling and hot water demand through the use of renewable sources. These renewable energy sources can be defined as „renewable non-fossil energy sources: wind, solar, air, geothermal, water, wave, tidal, hydropower, biomass, landfill gas, sewage treatment plant gas and biogases. (EHPA)

Various methods can be applied for using ambient heat for heating and hot water supply of households as well as for the air conditioning of buildings:
 The use of ground water as heat source.
 Direct expansion/terrestrial heat register.
 Glycol and water-heat pipes
 Heat pipes without circulation pumps (CO2-heat pipes)
 Air as a heat source

3. ADVANTAGES OF THE HEAT SOURCE AIR

Ambient air is a heat source that is unlimited, available anywhere and can be utilized without any permissions.

For heat provision using air the utilization of ambient heat is necessary with larger heat loads respectively rated useful heat since only ambient air can make available enough air capacity for the necessary performance. These heat pumps based on ambient air are very multifarious in their applications and versions.

While other heat sources need a certain phase for recovery to get stored up after the temperature withdrawal, the natural recovery of the heat source ambient air happens during use.

Currently many house owners do not even consider utilizing the heat pump technology. They consider the installation of the ground source heat pump as too sophisticated. For these customers the heat pump technology with ambient air as a heat source promises a large benefit. As a rule ambient air conducted heat pumps need no sophisticated heat source facility since the airflow is relatively simple to implement. For the air heat exchanger nor earth movement neither drillings have to be carried out, the energy saving in comparison to fossile fuels amounts to approx. 50 %
Air is also very suitable as a heat source due to the fact that no safety-related facilities - as with a water/water system - are necessary. Furthermore there is no danger of leakage.

4. TECHNICAL UTILIZATION OF AMBIENT AIR THROUG HEAT PUMPS

Using an air channel the ambient air is transported to the evaporator. The evaporator passes on the heat, which is developed in the refrigerant cycle, through the condensor to the heat utilization device.

The fluctuation in temperature of the heat source is varied throughout the year and shows the largest range between high ambient temperature in summer and the transition period as well as relatively low temperatures in winter. At decreasing temperatures the heat demand of a building rises. At the same time, though, the heat pump’s heat output and coefficient of perfomance decrease. The new air/water heat pumps, though, reach flow temperatures of 65 degrees even at temperatures below zero. These temperatures are suited to operate existing radiator heaters. Through the, in OCHSNER air/water heat pumps integrated defrosting device a proper function even at temparatures below –15 degrees is given.

The area of application retrofit gains more and more importance. In many cases a retrofit of system using ground or water as a heat source is not possible, since the heat source is not sufficiently available or the existing space conditions prevents retrofit. Air heat pumps are not subject to such restrictions and therefore, in many cases, offer the only posibility of retrofit.

Ambient air, though, is not only suitable for restoration but also for new buildings with a lot too small for the necessary area of a flat collector. Often the garden area is used for other functions (swimming pool, garden hut) whereas the, for the collector necessary, area is lost. Air/water heat pumps are the ideal solution for buildings with low heat demand. In Austria the market for passive houses, such with a useful heat demand of max. 15 kWh/m2a, gains increasing importance. For such highly efficient buildings any other heating system is oversized. Air/water heat pumps, that cover the necessary remaining energy, are very suitable for this application.

Mostly no detailed planning of the heat source facility is necessary with ambient air heat pump facilities as for example with earth coupled heat sources. The evaporator with the, for the airflow responsible, fan is already an ex factory part of the heat pump. During installation only the connections and the air duct cross section must be considered to provide the, at any time, necessary air volume. 
Sound emission
Modern air/water heat pumps excel through very low operating sound. Apart from that the weather-resistant casing of the heat pump is also sound insulated as is the version for interior installation. The heat pump’s sound emission depend on the local circumstances, is, however, steady in its performance. According to norm VDI 2058 the following sound emission are not allowed to be exceeded

The Ochner air/water heat pumps fall significantly below these values and therefore count as the most quiet facilities.

5. DIFFERENT DESIGN OF AIR/ WATER HEAT PUMPS

Ambient air-heat pumps are distinguished in different designs. The differences are only in the respecitive kind of installation. One distinguishes between interior installation, exterior installation and split construction.

5.1 Split facilities

Especially efficient are air heat pumps in split construction. The charactarization of split construction means that the facility’s refrigerant cycle is split. The refrigerant piping that is directed into the house from the evaporator is  connected to the heat pump’s refrigerant cycle. The OCHSNER split air/water heat pumps offer the advantage that the heat pump (compressor, condenser, electronics) is placed within the building and is therefore weather protected. The fan blows the ambient air through the separately installed evaporator. The evaporator herewith withdraw heat from the ambient air. Then the working medium is transported to the heat pump inside the house. Possible maintenance work can be carried out easily in winter. The heat is placed in immediate vicinity to the heat utilitzation facility and heat can therefore be delivered to the heat distribution system without loss. Fig. 2 shows the split-evaporator

This design needs the smallest wall opening for duct of the supply line. Furthermore the refrigerant pipings do not necessarily have to be installed in the earth since the evaporator itself can be placed significantly closer to the building.

The evaporators of the split facility are equipped with the extremely quiet axial fan. They are installed outdoors. The connections are made with cooling pipes, elaborate and noisly air channels are omitted.

Using the incombustible refrigerant R 407C makes the installation possible at any place. Keeping it frost free is not necessary since the cooling agent in the evaporator cannot freeze even after longer standstill of the facility.

Installation of machine part
The use of the machine part with safety working appliance is possible in any room that is dry and not threatened by frost. The installation should be carried out on an even, horizontal area. The device’s location should be chosen in a way that makes operation and maintenance comfortable. Normally full thermal compressors (reciprocating or scroll compressors are used which have the advantage that they can guarantee a completely quiet operation). Mostly stainless steel plate heat exchangers are used for the condenser.

Installation of evaporator
Split facilities allow the use of large, powerful evaporators and slow running, quiet exhausters. The installation of the evaporator can be carried out in such a way that the distance to the heat pump can amount to 20 m. Likewise the installation on flat or pitched roof is possible since the max. height difference can amount to 20 m as well.

Even if the split design can also be installed in new buildings they are especially suitable for retrofit. This because it is very simple to insert cooling lines into the house.

5.2 Compact systems
These devices, depending on the design, are suitable for installation outdoor or indoor. The ambient heat is sucked in by the integrated fan and blown through the horizontally installed evaporator. Hereby quiet axial fans are used.

The installation of the compact system is possible within the building, but also outdoors. 

Interior installation
The heat pump is placed within the building in a housing technology room in immediate vicinity to the hot water tank. If the airflow runs through the wall sufficient distance must be considered to avoid a short circuit. Hereby also the wind conditions must be considered. The airflow can be made over corner zu exclude the air circuit. The air can also be redirected targeted through suction hoods.

Outdoor installation
If the facility is installed outdoors the connection between the heat pump and the building is through the heat supply and return system, an electrical feed line as well as the control wire. The lines as well as the electricity and control wires are installed in the floor. The devices for the outdoor installation can be placed at any area outdoor. Any part of the refrigerant cycle is integrated in this compact system and therefore no air channels are necessary. The casing is designed weather-restistant. Fig. 4 shows the OCHSNER compact heat pump „Air station plus“

Refrigerant Cycle
As a rule the refrigerant cycle is equipped with a full thermal compressor as well as an integrated, internal overload protector. The devices dispose of lamellae evaporator of copper pipes with aluminium lamellaes. Axial Axial exhausters, but also radial exhausters, are used for a low noise development. As well as in split devices clorine-free refrigerants are used in any case. Hereby the safety refrigerants ( R 407C, R 404A, R 410A, R 134a etc.) are concerned.

Design for 65˚C flow temperature
If a heat flow temperature of 65˚C utilizing the heat source ambient air should be reached a special technique or a double-stage compression is necessary. Especially at high temperature hoisting at outdoor temperatures of approx. -15˚C conventional refrigerant cycles would operate outside the tolerable limits of use. Through the cycle process with partial current steam injection the area of application is not only extended, but also the coefficient of performance and heat output are improved.

6. THE NEW AIR/ WATER HEAT PUMPs BY OCHSNER

The so called „GOLF“ series heat pumps and the „air station plus“ are models of success in modern heating technology. The new air/water heat pumps are available in compact as well as in split design. For this reason the heating operator can be offered the design that is most suitable to his needs.

With the split-construction the heat pump is installed indoor, protected from the weather.

The „super-split-evaporator is installed outdoors, as near to the house as possible. The fan draws air over the evaporator and an automatic defrost unit keeps the evaporator free of ice and snow. The generous sizing of the unit, the construction and the slow rotation of the fan ensure very silent operation all year long.

The super split Evaporator requires very little space. The distance to the house shouldn`t be more than 20 meters. Ideal installation is on the south side of the house, where solar gains provide additional warmth. The evaporator can, however, be installed in any open space. In contrast to conventional outdoor air source heat pump units, the Super-Split-System is not in danger of freezing, even in a power outage, and has no piping losses. In comparison to compact indoor units, the complicated placement of the often times loud air ducts can be eliminated.
The O-Tronic classic heat pump manager makes the GOLF Super-Split independent of winter weather and enables it to achieve high performance coefficients. The O-Tronic classic is a weather driven comfort controller developed specially for heat pumps and has been proven through years of operation. Many functions such as a diagnostic system and safety functions are integrated.

The GMLW model series has been developed especially for optimal use of outdoor air as heat source. The „GOLF plus“ series, offer standard heating supply temperatures up to 65˚C. The heat pump can also be used for cooling purposes in summer without additional air conditioning system. To work in the cooling mode, the heat pump principle is reversed. The indoor air is cooled and the heat is given off outdoors using the Super-Split-Evaporator. The Super-Split evaporator dissipates the surplus heat to the outside and the „heat“ distribution system (e.g. the wall heating system, radiant floors) becomes a cooling system.

Fig.5: GOLF Air/water Heat pump in heating and cooling mode
      

The new generation of heat pumps utilizes the refrigerant R407C as well as new scroll compressors.

This model is not only suitable for new buldings, but also for retrofits of heating systems in existing buildings. No expensive or complicated excavation or drilling work is required, as is with ground source systems. Also air ducts, which are needed in compact indoor installations, are not required.

Drilling of finger-thick holes in the outer wall is all that is necessary to connect the indoor and outdoor units of the Super-Split-System. Outdoors, the space requirement is minimal, as only the evaporator is installed on a concrete base.

If desired the Super-Split-System can also be used for hot water preparation with an external hot water tank. The O-Tronic-Controller automatically ensures that sufficient hot water is available at the proper temperature. The air/water heat pump can also be used for heating a swimming-pool.

Advantages of the Super-Split
 Reliable and quiet operation with proven technology
 Heating and cooling possible
 Supply temperatures up to 65˚C at -16˚C outdoor air temperature
 Also suited for radiator heating systems
 Ideal for heating system retrofits in older buildings
 Installation of evaporator outdoors to increase efficiency
 Heat pump unit installed in the protection of the home
 Only finger-thick lines are placed through outer wall
 No air ducts required
 No excavation or drilling work required
 High performance coefficients, even at low outdoor temperatures
 Domestic hot water preparation and pool heating options available


What Heat Source to use

Tip: The heat source with the highest temperature level brings the highest coefficient of performance and thus lowest heating costs.
 

Water

Earth Coupled Systems

Horizontal earth collectors use about 98 % solar heat stored in the ground. The soil temperature stays at a considerably high level of temperature even during very cold winter days, enough to heat your home. There are different ways to use the energy from the soil: