Patent Description:
Known heat source units generally comprise an external housing accommodating at least the compressor, the heat source heat exchanger and an electric box accommodating electrical components configured to control the air conditioner, particularly the refrigerant circuit of the heat pump.

At least some of the electrical components contained in the electric box require cooling. For this purpose <CIT> discloses an electric box having an air passage comprising an air inlet and an air outlet opening into an interior of the external housing and a fan configured to induce an air flow through the air passage from the air inlet to the air outlet for cooling the electrical components.

The electrical components transfer heat to the air flowing in the air passage. The heated air is subsequently introduced into the interior of the external housing. A similar disclosure may be found in <CIT>, which discloses a heat source unit for an air conditioner according to the preamble of claim <NUM>.

<CIT> additionally suggests a heat dissipating plate disposed with a first portion in direct contact with an electrical component and with a second portion outside the electric box. A refrigerant piping connected to the refrigerant circuit is coupled to the second portion of the heat dissipating plate. It may for maintenance reasons or to make modifications of a controller contained in the electric box be required to access the electric box. In the configuration of <CIT> the refrigerant piping has to be disassembled from the second portion of the heat dissipating plate. Due to the fragility of the refrigerant piping, there is a risk of damaging the refrigerant piping.

<CIT> discloses an air conditioner including a control box having a space formed therein, a PCB arranged to form an air circulation passage in the space, the PCB having a plurality of electric components mounted thereto, a cooling module for making a first electronic component of the plurality of electronic components to heat exchange with refrigerant, and a circulating fan arranged in the air circulation passage to make air flow to a second electric component of the plurality of electric components after being cooled by the cooling module, thereby dissipating heat from an inside of the control box with a mixed cooling system of a refrigerant cooling system and an air cooling system, efficiently.

In addition, hot refrigerant components such as the compressor, a liquid receiver or an oil separator accommodated in the external housing of the heat source unit dissipate heat as well.

The heat source unit is under certain circumstances disposed in an installation environment or space, such as installation rooms inside a building. This is particularly the case when using water as the source of heat. Because the heat source unit as a whole dissipates heat, the temperature in the installation room may increase, which is perceived disadvantageous. If other equipment is also installed in the installation room and the other equipment is sensible to high temperatures, even additional cooling of the installation room may be required.

In view of the aforesaid, it is an object to provide a heat source unit for an air conditioner and an air conditioner having such a heat source unit in which an amount of heat dissipated by the heat source unit can be reduced or even be eliminated.

A basic idea to address this problem is the provision of a cooling heat exchanger to be connected to the refrigerant circuit of the air conditioner and flown through by a refrigerant. The cooling heat exchanger is arranged so as to be flown through by the air flow induced through the air passage of the electric box, whereby the air is cooled. As a result, an amount of heat dissipated by the heat source unit, particularly the air expelled from the electric box after cooling the electrical components, can be reduced or even be eliminated. Yet, there is a certain risk that condensation water, which is formed on the cooling heat exchanger due to the temperature difference and humidity in the air, comes into contact with the electrical components. Thus, a further object may be to provide a heat source unit and an air conditioner having such a heat source unit in which the risk of condensation water coming into contact with electrical components of the electric box is minimized.

Moreover, it may be an aim to provide a heat source unit for an air conditioner and an air conditioner having such a heat source unit in which a cooling heat exchanger to cool the air flowing through the air passage of the electric box recovers the heat dissipated from the electrical components and uses the heat in the refrigerant circuit of the air conditioner. In this connection, it would be beneficial if the cooling heat exchanger is arranged in the refrigerant circuit so as to enable heat recovery at the same time minimizing any negative effects on a possible capacity and operation of the air conditioner. Further, a simple control mechanism for controlling the refrigerant flow through the cooling heat exchanger is desired to minimize costs.

An even further object may be to provide a heat source unit for an air conditioner and an air conditioner having such a heat source unit in which access to the electric box is simplified for ease of maintenance.

According to an aspect of the present invention and for solving at least one of the above objects, a heat source unit as defined in claim <NUM> is suggested. Further embodiments including an air conditioner having such a heat source unit are defined in the dependent claims, the following description and the drawings.

In accordance with one aspect, a heat source unit for an air conditioner is suggested. In general, the air conditioner may be operated in a cooling operation for cooling a room (or a plurality of rooms) to be conditioned and optionally in heating operation for heating a room (or a plurality of rooms) to be conditioned. If the air conditioner is configured for more than one room even a mixed operation is conceivable in which one room to be conditioned is cooled whereas another room to be conditioned is heated. The suggested air conditioner comprises a refrigerant circuit. As previously indicated the refrigerant circuit may constitute a heat pump and comprise at least a compressor, a heat source heat exchanger, an expansion valve and at least one indoor heat exchanger. The heat source unit according to one aspect comprises an external housing defining an interior of the heat source unit and an exterior of the heat source unit. The external housing accommodates at least the compressor, the heat source heat exchanger, an electric box and a cooling heat exchanger. The cooling heat exchanger may function as an evaporator in the refrigerant circuit and may, hence, also be referred to as an evaporator. The external housing may further accommodate an expansion valve, a liquid receiver, an oil separator and an accumulator of the refrigerant circuit.

The components of the refrigerant circuit accommodated in the external housing, particularly the compressor and the heat source heat exchanger are to be connected to the refrigerant circuit. Further, the heat source heat exchanger is configured to exchange heat between a refrigerant circulating in the refrigerant circuit and a heat source, particularly water even though air and ground are as well conceivable. The electric box accommodates electrical components which are configured to control the air conditioner, particularly the heat pump. The electric box has at least a top and side walls. A bottom end of the electric box may either be open or has a bottom. The side walls extend in general along a vertical direction from the bottom to the top. "Along the vertical direction" in this context does not require that the side walls are oriented vertical even though this is one possibility. Rather, the side walls may also be inclined to the vertical direction. As long as the side walls are not angled more than <NUM>° to a vertical direction, the side walls are to be understood as extending along the vertical direction. In order to enable cooling of at least some of the electrical components contained in the electric box, an air passage comprising an air inlet and an air outlet is suggested. According to an aspect at least the air outlet is arranged in the electric box so as to open into the interior of the external housing. This is particularly preferred if also hot refrigerant components accommodated in the external housing are to be cooled as will be described later. Yet, it is also conceivable that the air outlet opens to the external of the external housing. The air inlet may either be arranged so as to open to the exterior of the external housing or into the interior of the external housing. An air flow through the air passage from the air inlet to the air outlet may be induced by natural convection. Alternatively, a fan may be provided either at the air inlet or the air outlet to induce the air flow as described later. A cooling heat exchanger to be connected to the refrigerant circuit of the air conditioner is suggested so as to minimize the amount of heat from the electrical components being dissipated into the surroundings of the heat source unit. The cooling heat exchanger is arranged at one of the side walls of the electric box so as to be flown through by the air flow and exchange heat between the refrigerant and the air flow.

Accordingly, in one case the air introduced through the air inlet may be cooled by heat transfer between the air and the refrigerant flowing through the cooling heat exchanger, whereby the temperature of the refrigerant is increased and at least some of the refrigerant evaporates. Accordingly the temperature of the air flowing into the air passage through the air inlet is lower than the temperature of the air in the interior of the external housing or the environment of the heat source unit. Thus, the air expelled through the air outlet may have a temperature similar to that of the air in the external housing or the environment of the heat source unit. As a result, the electrical components do not further heat up the interior of the external housing and the amount of heat dissipated to the exterior (environment) can be reduced. In addition, disposing the cooling heat exchanger at the side walls of the electric box enables efficient use of a large heat exchange surface of the cooling heat exchanger without the need of increasing the width and/or the height of the electric box for fixing the cooling heat exchanger. Thus, this arrangement makes beneficial use of the available mounting space. In addition, arranging the cooling heat exchanger at a side wall of the electric box assists preventing any condensation water from coming into contact with the electrical components in the air passage.

If the cooling heat exchanger is disposed upstream of the electrical components in the air passage it is conceivable that sweat is generated on the inside of the electric box because of the relatively cool air introduced into the air passage and the high temperature difference between the air passage and the electric box. To prevent the formation of sweat, the cooling heat exchanger may be disposed downstream of the electrical components to be cooled in the direction of the air flow. According to one aspect, the cooling heat exchanger may be disposed at the air outlet of the air passage. Accordingly, the air flowing into the air inlet from the interior of the external housing flows through the air passage and cools the electrical components in the air passage, whereby the temperature of the air increases. Subsequently, the air is cooled by flowing through the cooling heat exchanger, wherein the temperature of the refrigerant flowing through the cooling heat exchanger is increased and the refrigerant evaporates. The air expelled from an air outlet of the cooling heat exchanger has than a temperature which is at least similar if not the same as the temperature of air in the interior of the external housing and may even be lower. Hence, also in this case the electrical components do not further heat up the air in the interior of the external casing and hence heat dissipation to the exterior surroundings may be reduced. Furthermore, there is a risk that condensation water is formed on the surfaces of the cooling heat exchanger as explained earlier. Because the cooling heat exchanger is arranged downstream of electrical components of the electrical components and/or a heat sink heat conductively connected to electrical components of the electrical components which are disposed in the air flow, i.e. in the air passage, the risk is reduced that condensation water will come in contact with the electrical components or the heat sink. In particular, as the air flow is away from the electrical components and the heat sink in the air passage, the air flow will rather transport any condensation water away from the electrical components and the heat sink. Moreover, disposing the cooling heat exchanger downstream of the electrical components to be cooled has the advantage that a larger amount of heat may be transferred to the refrigerant so that heat recovery and the use of heat in the refrigerant circuit are improved.

As previously mentioned, it is conceivable to provide at least one fan to induce the air flow through the air passage from the air inlet to the air outlet. Accordingly, efficiency of cooling of the electrical components and the heat transfer between the air flow and the refrigerant in the cooling heat exchanger may be enhanced because a larger air flow may be generated as compared to natural convection.

According to an aspect, the fan is disposed at the air outlet. This has the advantage that maintenance of the fan is simplified, because the fan is easily accessible even from the outside of the electric box.

To even further improve the effect of preventing condensation water coming in contact with the electrical components and the heat sink, it may be advantageous to dispose the cooling heat exchanger downstream of the fan. Hence a relatively large air flow "blows" any condensation water on the cooling heat exchanger away from the air passage and the air outlet. Moreover, the fan can then form a barrier between the electrical components and the air passage and the cooling heat exchanger further preventing any condensation water from entering the air passage. A further advantage of this configuration may be that the efficiency of the fan is higher if it is disposed upstream of the cooling heat exchanger so that less power is required to drive the fan.

As indicated in the introductory portion, also other components of the refrigerant circuit (heat pump) are accommodated in the external housing dissipating heat because of hot refrigerant flowing through the components in use. One example of such a hot refrigerant component is the compressor. Other examples are an oil separator or a liquid receiver. In order to decrease the amount of heat dissipated from these components to the exterior of the heat source unit, the cooling heat exchanger may be oriented and particularly an air outlet of the cooling heat exchanger may be oriented or configured to expel the air leaving the cooling heat exchanger in a direction of hot refrigerant components accommodated in the external housing comprising at least one of the group consisting of the compressor, an oil separator and a liquid receiver. In one particular example, the cooling heat exchanger may have a duct connecting at one end to the air outlet of the air passage and at an opposite end to an air inlet of the cooling heat exchanger. The duct may form a passage changing the direction of the air flow from the air outlet of the electric box to the air inlet of the cooling heat exchanger. Thus, common plate-shaped heat exchangers may be used as cooling heat exchanger. The change of the flow direction is then achieved by the duct and the common plate - shaped heat exchanger is attached in an inclined orientation relative to the vertical direction to the duct, whereby the air outlet of the heat exchanger (cooling heat exchanger) is directed to the direction of the hot refrigerant components, whereby the air flow is directed on and cools the hot refrigerant components within the external housing. As a consequence, the heat dissipated from the hot refrigerant components to the interior of the external housing and, hence, the environment of the heat source unit can be reduced even further.

According to further aspect, the air outlet of the air passage is located closer to a top than to a bottom of the external housing. In a particular embodiment, the air outlet of the air passage is located closer to the top than to a bottom end of the electric box. The above arrangement provides for the beneficial effect that natural convection within the interior of the external housing is promoted because relatively cool air is expelled from the air outlet of the air passage at a relatively high position within the external housing which because of natural convection than automatically flows down to the bottom of the external housing.

According to another aspect, the cooling heat exchanger may be connected to a bypass line branched from a liquid refrigerant line and a gas suction line. "Liquid refrigerant line" is in this context to be understood as a line of the refrigerant circuit in which the flowing refrigerant is in the liquid phase. "Gas suction line" is in this context to be understood as a line of the refrigerant circuit on a suction side of the compressor in which gaseous refrigerant flows. According to an example, the liquid refrigerant line is a line connecting the heat source heat exchanger and the indoor heat exchanger. Furthermore, the bypass line may be connected to the liquid refrigerant line in this example with an expansion valve interposed between the bypass line and the heat source heat exchanger. In one particular example, the gas suction line may be a line connected to a suction side of the compressor with one or more components, such as an accumulator, that may be interposed. To put it differently, the cooling heat exchanger is connected to a bypass line branched from a liquid refrigerant line, e.g. connected to the heat source heat exchanger, and a gas suction line, e.g. connected to a suction side of the compressor. Yet, it is also conceivable that an accumulator is disposed between the connection of the bypass line to the gas suction line and the suction side of the compressor. The benefit of this aspect is that the cooling heat exchanger may always be operated as long as the compressor is operating so that a reliable system is obtained without negatively affecting the refrigerant circuit of the air conditioner. In addition, this arrangement provides for an efficient use of the heat dissipated from the electrical components in the refrigerant circuit during heating operation of the air conditioner.

The bypass line may have an expansion valve, wherein the opening degree of the expansion valve is controllable. Yet, according to an embodiment, the bypass line may have a valve and a capillary both upstream of the cooling heat exchanger. According to one embodiment, the valve is switched ON/OFF only, that is the valve is (completely) opened/closed only. The valve may be a solenoid valve. The use of a controlled expansion valve enables a more sophisticated control. Yet, this is not under all circumstances necessary with respect to the cooling heat exchanger flown through by the air flow. Thus, the use of a valve and a capillary instead of the expansion valve provides for a simpler configuration, which is less costly and can dispense the more complicated control logic necessary when using an expansion valve. In either case, it is possible to adapt the cooling performance of the cooling heat exchanger on the needs of the system and the circumstances such as operation conditions of the air conditioner.

As previously indicated, there is a certain risk that condensation water is accumulated on the surfaces of the cooling heat exchanger. According to an aspect, a bottom end portion of the cooling heat exchanger slopes downward towards an air outlet of the cooling heat exchanger. For example, the cooling heat exchanger may have a bottom plate being arranged so as to slope downward towards the air outlet of the cooling heat exchanger. Accordingly, any condensation water which drops or flows down from the cooling heat exchanger will be guided by the bottom end portion, e.g. the bottom plate, from an air inlet of the cooling heat exchanger to an air outlet of the cooling heat exchanger, at which position the condensation water may drop down into a drain pan accommodated in the external housing. Thus, any condensation water is guided away from the air inlet of the cooling heat exchanger. As a result, it can surely be prevented that any condensation water will flow into the air passage and come in contact with the electrical components or the heat sink.

According to an aspect the cooling heat exchanger has a plurality of fins and tubes, wherein the fins are arranged with a longitudinal extension along a vertical direction. The fins are in principle plate shaped having a length and a width much larger than a height. Thus, the length and the width define a main surface of the fins. The tubes generally extend perpendicular to the main surfaces of the fins. "Along a vertical direction" is, in this context, to be understood in the same manner as explained with respect to the side walls above. In particular, the fins do not need to be oriented vertical but merely need to extend in a direction from a bottom to a top of the external housing. In one example, the fins are with a longitudinal extension inclined relative to the vertical direction. This is particularly the case, if the cooling heat exchanger is inclined to expel the air toward the hot refrigerant components in the external housing as described above. Due to the orientation of the fins along a vertical direction, any condensation water flows along the fins from a top end portion to the bottom end portion of the cooling heat exchanger. Particularly in combination with the bottom end portion sloping downward toward the air outlet of the air conditioner, this ensures that all condensation water of the cooling heat exchanger is guided away from the air passage.

A further aspect concerns an air conditioner having a heat source unit according to any aspect as described above. The heat source unit is connected to at least one indoor unit having an indoor heat exchanger forming the refrigerant circuit. As previously indicated, the air conditioner has the refrigerant circuit which may constitute a heat pump. Hence, the refrigerant circuit may comprise the compressor, the heat source heat exchanger, an expansion valve and at least one indoor heat exchanger to form a heat pump circuit. Additional components as known for air conditioners may be included as well such as a liquid receiver, an accumulator and an oil separator. According to one aspect, the air conditioner uses water as a heat source. According to a further aspect, the air conditioner is mounted in a building comprising one or more rooms to be conditioned and the heat source unit is installed in an installation environment or space, such as an installation room of the building.

Further aspects, features and advantages may be found in the following description of particular examples. This description refers to the accompanying drawings.

In the following description and the drawings, the same reference numerals have been used for the same elements and repetition of the description of these elements in the different embodiments is omitted.

<FIG> shows an example of an air conditioner <NUM> installed in an office building. The office building has a plurality of rooms <NUM> to be conditioned such as conference rooms, a reception area and working places of the employees.

The air conditioner <NUM> comprises a plurality of indoor units <NUM> to <NUM>. The indoor units are disposed in the rooms <NUM> and may have different configurations, such as wall-mounted <NUM>, ceiling mounted <NUM> or duct-type indoor units <NUM>.

The air conditioner further comprises a plurality of heat source units <NUM>. The heat source units <NUM> are installed in an installation room <NUM> of the office building. Other equipment such as servers (not shown) may be installed in the installation room <NUM> as well. In the present example, the heat source units <NUM> use water as heat source. In the particular example, a water circuit <NUM> is provided which is connected to a boiler, dry-cooler, cooling tower, ground loop or the like. The water circuit <NUM> may as well have a heat pump circuit including a refrigerant circuit. An outdoor unit comprising the heat source heat exchanger of this heat pump circuit may be disposed on the roof of the office building and use air as the heat source. Yet, the concept of the heat source unit of the present disclosure is also applicable to other heat sources such as air or ground.

In operation one or more of the indoor units <NUM> to <NUM> may be operated to cool the respective rooms <NUM> whereas others are operated to heat the respective rooms.

A simplified schematic diagram of the air conditioner is shown in <FIG>. The air conditioner <NUM> in <FIG> is mainly constituted by an indoor unit <NUM> and the heat source unit <NUM>. Yet, the air conditioner <NUM> in <FIG> may also have a plurality of indoor units <NUM>. The indoor units may have any configuration such as those described with respect to <FIG> above.

Further, <FIG> shows the refrigerant circuit constituting a heat pump. The refrigerant circuit comprises a compressor <NUM>, a <NUM>-way valve <NUM> for switching between cooling and heating operation, a heat source heat exchanger <NUM>, an expansion valve <NUM>, and optional additional expansion valve <NUM> and an indoor heat exchanger <NUM>. The heat source heat exchanger <NUM> is additionally connected to the water circuit <NUM> as the heat source. When the compressor <NUM> is operated, a refrigerant is circulated in the refrigerant circuit.

In cooling operation, high-pressure refrigerant is discharged from the compressor <NUM>, flows through the <NUM>-way valve <NUM> to the heat source heat exchanger <NUM> functioning as a condenser whereby the refrigerant temperature is decreased and gaseous refrigerant condensed. Thus, heat is transferred from the refrigerant to the water in the water circuit <NUM>. Subsequently, the refrigerant passes the expansion valve <NUM> and the optional expansion valve <NUM>, wherein the refrigerant is expanded before being introduced into the indoor heat exchanger <NUM> functioning as an evaporator. In the indoor heat exchanger <NUM>, the refrigerant is evaporated and heat is extracted from the air in the room <NUM> to be conditioned, whereby the air is cooled and reintroduced into the room <NUM>. At the same time, the temperature of the refrigerant is increased. Subsequently, the refrigerant passes the <NUM>-way valve <NUM> and is introduced into the compressor <NUM> as low-pressure gaseous refrigerant at the suction side of the compressor <NUM>. In view of the aforesaid, the line connecting the heat source heat exchanger <NUM> and the indoor heat exchanger <NUM> is considered a liquid refrigerant line <NUM>. The line connecting the <NUM>-way valve <NUM> and the suction side of the compressor <NUM> is considered a gas suction line <NUM>.

In heating operation, high-pressure refrigerant is discharged from the compressor <NUM>, flows through the <NUM>-way valve <NUM> to the indoor heat exchanger <NUM> (dotted line of the <NUM> way valve <NUM>) functioning as the condenser, whereby the refrigerant temperature is decreased and gaseous refrigerant condensed. Thus, heat is transferred from the refrigerant to the air in the room <NUM> whereby the room is heated. Subsequently, the refrigerant passes the optional expansion valve <NUM> and the expansion valve <NUM>, wherein the refrigerant is expanded before being introduced into the heat source heat exchanger <NUM> functioning as an evaporator via the liquid refrigerant line <NUM>. In the heat source heat exchanger <NUM>, the refrigerant is evaporated and heat is extracted from water in the water circuit <NUM>. At the same time, the temperature of the refrigerant is increased. Subsequently, the refrigerant passes the <NUM>-way valve <NUM> (dotted line of the <NUM>-way valve <NUM>) and is introduced into the compressor <NUM> as low-pressure gaseous refrigerant at the suction side of the compressor <NUM> via the gas suction line <NUM>.

The refrigerant circuit shown in <FIG> further comprises a bypass line <NUM> branched from the liquid refrigerant line <NUM> and connected to the gas suction line <NUM>. In the particular example, the bypass line <NUM> is connected to the liquid refrigerant line <NUM> between the expansion valve <NUM> and the indoor heat exchanger <NUM>. If the optional expansion valve <NUM> is provided, the bypass line <NUM> is connected between the expansion valve <NUM> and the optional expansion valve <NUM>.

The bypass line <NUM> comprises a valve <NUM> which may assume an open and a closed position (ON/OFF). The valve <NUM> may be a solenoid valve. Furthermore, the bypass line <NUM> comprises a capillary <NUM>. In the particular example, the capillary <NUM> is disposed downstream of the valve <NUM> in the direction of the flow of refrigerant during cooling operation. Yet, the valve <NUM> may as well be disposed downstream of the capillary <NUM>.

Furthermore, a cooling heat exchanger <NUM> (described in more detail below) is connected to the bypass line <NUM> downstream of the capillary <NUM> and the valve <NUM> in the direction of flow of refrigerant during cooling operation. The function of this cooling heat exchanger <NUM>, the valve <NUM> and the capillary <NUM> will be described further below.

In one example, the components contained in the dotted rectangle indicating the heat source unit <NUM> in <FIG> are accommodated in an external housing <NUM> (see <FIG>) of the heat source unit <NUM>.

As schematically indicated in <FIG> and shown in more detail in <FIG>, the external housing <NUM> has side walls <NUM> and a top <NUM> both shown in a dotted lines. Furthermore, the external housing <NUM> has a bottom <NUM>. Thus, the external housing <NUM> defines an interior <NUM> of the external housing <NUM> and an exterior <NUM> of the external housing <NUM> which in one example may be the installation room <NUM> as an example of an installation environment or installation space (see <FIG>). In the present example, the bottom <NUM> has a drain pan <NUM> for collecting any condensation water accumulated in the external housing <NUM>. The bottom <NUM> supports the remaining components of the heat source unit <NUM> to be explained in the following. According to one example, none of the components contained in the external housing <NUM> is fixed to the side walls <NUM> or the top <NUM>, but all components are directly or indirectly, via the support structures, fixed to the bottom <NUM>.

As an example, the compressor <NUM>, and a liquid receiver <NUM> commonly used in refrigerant circuits of air conditioners are shown as a components accommodated in the external housing <NUM>. Further components are an oil separator <NUM> and an accumulator <NUM> (see <FIG>). In this context, the compressor <NUM>, the liquid receiver <NUM> and the oil separator <NUM> are considered as hot refrigerant components, because at least a proportion of the refrigerant passing through these components is gaseous and hot. The accumulator <NUM> in contrast is considered as a cold refrigerant component as only low pressure refrigerant passes through the accumulator <NUM>.

The external housing <NUM> may have vents <NUM> to allow ventilation of the interior <NUM> in case the later described zero heat dissipation control is not active.

Furthermore, the heat source unit <NUM> comprises an electric box <NUM>. The electric box <NUM> has the shape of a parallelepiped casing, but other shapes are conceivable as well. In the example, the electric box <NUM> has a top <NUM>, the side walls (in the present example four side walls, namely a back <NUM>, a front <NUM> and two opposite sides <NUM>) and a bottom <NUM>. In other embodiments, the bottom may be open. The electric box <NUM> has a height between the bottom end <NUM> and the top <NUM>, a depth between the back <NUM> and the front <NUM> and a width between the two opposite sides <NUM>. In the present embodiment, the electric box <NUM> is longitudinal having a height larger (at least twice as large) than the depth and the width.

The electric box <NUM> accommodates a plurality of electrical components <NUM> configured to control the air conditioner and particularly its components such as the compressor <NUM>, the expansion valves <NUM> and <NUM> or the valve <NUM>. The electrical components <NUM> are schematically shown in <FIG> only.

The electric box <NUM> further defines an air passage <NUM> having an air inlet <NUM> and an air outlet <NUM>. In the present embodiment, the air inlet <NUM> is disposed closer to the bottom <NUM> or the bottom end of the electric box <NUM> than the air outlet <NUM>. Even more particular, the air outlet <NUM> is located adjacent to the top <NUM> of the electric box <NUM>. Due to the longitudinal configuration of the electric box <NUM> and it is orientation with respect to the longitudinal extension along a vertical direction, the air outlet <NUM> is located adjacent to a top <NUM> of the external housing <NUM> (closer to the top <NUM> than to the bottom <NUM>). In addition, both the air inlet <NUM> and the air outlet <NUM> open into the interior <NUM> of the external housing <NUM>.

The electrical components <NUM>, which require cooling, are either directly disposed in the air passage <NUM> as shown in <FIG> and/or a heat sink is provided which is heat conductively connected to electrical components to be cooled and the heat sink is directly disposed in the air passage <NUM>.

Furthermore, the present embodiment shows a fan <NUM> to induce an air flow <NUM> (arrows in <FIG>) from the air inlet <NUM> to the air outlet <NUM> through the air passage <NUM>. Accordingly, the air passes the electrical components <NUM> for cooling, wherein heat is transferred from the electrical components either directly or via the mentioned heat sink to the air flowing through the air passage <NUM>. Certainly, also more than one fan <NUM> may be provided.

In the present embodiment, the fan <NUM> is arranged at the air outlet <NUM> of the air passage so that air from the interior <NUM> of the external housing <NUM> is sucked into the air inlet <NUM> passes through the air passage <NUM> and is expelled to the interior <NUM> of the external housing adjacent to the top <NUM> of the external housing <NUM>. Accordingly, natural convection is assisted in that relatively cool air is expelled at the top and will naturally flow down towards the bottom <NUM>.

Furthermore and as shown in <FIG>, and <FIG>, the cooling heat exchanger <NUM> is arranged downstream of the electrical components <NUM> as seen in the direction of the air flow <NUM>. In the particular example, the cooling heat exchanger <NUM> is also disposed at the air outlet <NUM> of the air passage <NUM> and even downstream of the fan <NUM> in the direction of the air flow <NUM>. In one example, the cooling heat exchanger <NUM> is attached to the air outlet <NUM> via a duct <NUM>. The duct <NUM> forms an air passage between the air outlet <NUM> of the air passage <NUM> and an air inlet <NUM> of the cooling heat exchanger <NUM>. The duct <NUM> can be used to change the direction of the air flow <NUM> and/or to mount a commonly known parallelepiped heat exchanger has the cooling heat exchanger <NUM> in an angled fashion as will be described later.

As may be best seen in <FIG>, the cooling heat exchanger <NUM> has a plurality of tubes <NUM> curved at end portions of the cooling heat exchanger <NUM> and passing a plurality of fins <NUM> schematically indicated in <FIG>. The fins <NUM> are longitudinal, plate shaped and extend with their longitudinal extension along a vertical direction, i.e. between the bottom <NUM> and the top <NUM>. It is to be understood, that extending along a vertical direction is as long realized as a longitudinal centerline of the fins <NUM> in a side view as in <FIG> does not intersect a vertical line at an angle of more than <NUM>°. The fins <NUM> are flat and have a longitudinal extension (lengths) and widths much larger than the height, whereby a main surface of the fins <NUM> is defined by the length and the width.

In the particular example, the cooling heat exchanger <NUM>, and particularly the longitudinal direction of the fins <NUM>, is angled by an angle α (see <FIG>) relative to the vertical direction. Accordingly, an air outlet <NUM> of the cooling heat exchanger is oriented such that the air flow <NUM> is directed toward hot refrigerant components, in the present example the compressor <NUM>, the liquid receiver <NUM> as well as an oil separator <NUM> (see <FIG>). The angle α may be in a range between <NUM>° and <NUM>°. As a result, the air cooled by the cooling heat exchanger <NUM> and expelled from the air outlet <NUM> of the cooling heat exchanger <NUM> is also used to cool one or more of the hot refrigerant components. Consequently, the amount of heat dissipated by the heat source unit <NUM> as such can be reduced.

Moreover, the cooling heat exchanger <NUM> has a bottom end portion <NUM> such as a bottom plate. In the present embodiment, the bottom end portion <NUM> is downwardly inclined from the air inlet <NUM> of the cooling heat exchanger <NUM> towards the air outlet <NUM> of the cooling heat exchanger <NUM>. In other words the bottom end portion <NUM> slopes downward towards a bottom <NUM> of the external housing <NUM>.

As indicated in the introductory portion, there is a risk that condensation water forms on the cooling heat exchanger <NUM> because of the humidity in the air in the interior <NUM> of the external housing <NUM> and the temperature difference. Yet, the particular example provides several means for guiding any condensation water away from the air outlet <NUM> of the air passage <NUM> so as to prevent any water from coming into contact with the electrical components <NUM> or the heat sink in the air passage <NUM>.

On the one hand and as mentioned above, the fins <NUM> are oriented with their longitudinal direction along a vertical direction. Accordingly, any condensation water formed on the main surfaces of the fins <NUM> flows down along the fins <NUM> and, hence, in a vertical direction due to gravity. On the other hand, the bottom end portion <NUM> of the cooling heat exchanger <NUM> is downwardly inclined. Accordingly, any condensation water which has flown down the fins <NUM> and reaches the bottom end portion <NUM> is guided by the bottom end portion <NUM> to the air outlet <NUM> of the cooling heat exchanger <NUM>. At a front edge of the air outlet <NUM> of the cooling heat exchanger <NUM>, the condensation water may drop down into the drain pan <NUM> in the bottom <NUM> of the external housing <NUM>. Thus, any condensation water is securely guided away from the air outlet <NUM> of the air passage <NUM>.

In addition and as previously mentioned, the cooling heat exchanger <NUM> is arranged at the air outlet <NUM> of the air passage <NUM> and consequently downstream of the electrical components <NUM> or the heat sink disposed in the air passage <NUM> in the direction of the air flow <NUM>. Accordingly, the air flow <NUM> "blows" any condensation water formed on the cooling heat exchanger <NUM> in a direction away from the air outlet <NUM> and the electrical components <NUM>. This configuration also assists preventing condensation water from coming into contact with sensible parts of the electric box <NUM>.

Even further, the fan <NUM> is disposed between the cooling heat exchanger <NUM> and to the electrical components <NUM> in the air passage <NUM>. Accordingly, the fan <NUM> can be considered as a partition separating the cooling heat exchanger <NUM> from the air passage <NUM>. Hence, the fan <NUM> is an additional barrier for condensation water and prevents the condensation water from entering the air passage <NUM>.

The electric box <NUM> is, in the present embodiment, supported so as to be rotatable about an axis of rotation <NUM>. The support structure <NUM> is shown in more detail in <FIG>. Thus, the electric box <NUM> is hinged to the support structure <NUM> so as to be movable between a use position shown in <FIG> and a maintenance position in which the electric box <NUM> is tilted about the axis of rotation <NUM> in a counterclockwise direction shown by the arrow in <FIG> and <FIG>. The axis of rotation <NUM> is located at a first end of the electric box close to the bottom <NUM>, i.e. opposite to the top <NUM>. Furthermore, the electric box <NUM> is at the top <NUM> releasably fixed to the support structure to retain the electric box <NUM> in the use position by bolts <NUM> (see <FIG>).

In the embodiment shown in <FIG>, the support structure <NUM> (best visible from <FIG>) is formed by a frame <NUM>. The frame <NUM> is fixed to the bottom <NUM> of the external housing <NUM>. The frame <NUM> has two upright columns <NUM>. The columns <NUM> are mounted to the bottom <NUM> of the external housing <NUM>.

Each of the columns <NUM> has at its bottom end close to the bottom <NUM> of the external housing <NUM> a slot <NUM>. A boss <NUM> is provided on either side <NUM> of the electric box <NUM> and engaged with one of the slots <NUM>. Different to the schematic view in <FIG>, the detailed representation of the slot <NUM> in <FIG> shows an inserting portion <NUM> used to insert the boss <NUM> into the slot <NUM> or to remove the boss <NUM> from the slot <NUM> and, hence, to completely remove the electric box <NUM> from the heat source unit <NUM>. The inserting portion <NUM> has an opening <NUM> at one end for introducing the boss <NUM>. Furthermore, an engagement portion <NUM> is formed at the opposite end of the inserting portion <NUM>. The engagement portion has a lower section <NUM> supporting the boss <NUM> in the use position in an upward direction and an upper section <NUM> supporting the boss <NUM> in the maintenance position in a downward direction. The axis of rotation <NUM> is formed by the bosses <NUM>. It is also clear from the side view of <FIG>, that the center of gravity <NUM> of the electric box <NUM> is arranged so that the electric box <NUM> tends to rotate about the axis of rotation <NUM> in a clockwise direction that is towards the interior <NUM> of the external housing <NUM>.

As previously mentioned, the electric box <NUM> may be releasably fixed to the frame <NUM> by bolts <NUM> (see <FIG>). When releasing the bolts <NUM> at the upper end near the top <NUM> of the electric box <NUM> from the frame <NUM>, the electric box may be rotated about the axis of rotation <NUM> or the bosses <NUM>, respectively, in a counterclockwise direction as will be explained in more detail below. For rotating the electric box <NUM> it is conceivable to provide a handle <NUM> (see <FIG>) in or at an outer surface of the electric box <NUM>.

The cooling heat exchanger <NUM> is in the present example together with the duct <NUM> fixed to the frame <NUM> by bolts. As may be best seen from <FIG>, the air outlet <NUM> or more particularly an opening <NUM> of the frame <NUM> facing the air outlet <NUM> of the air passage <NUM> is surrounded by an elastic sealing <NUM>. The elastic sealing <NUM> is as well fixed to the frame <NUM>. The sealing, particularly the contact surface of the sealing facing the electric box <NUM> defines a plane <NUM>. The center of gravity <NUM> is in a side view (<FIG>) disposed between the plane <NUM> and the axis of rotation <NUM> (formed by the boss <NUM>). Thus, the electric box <NUM> tends to rotate against the contact surface of the sealing <NUM> by gravity ensuring a proper contact with the sealing at the air outlet <NUM> between the outlet <NUM> and the cooling heat exchanger <NUM> and its optional duct <NUM>. Certainly, other or further possibilities to seal between the outlet <NUM> and the cooling heat exchanger <NUM> and its optional duct <NUM> are conceivable. For example, the sealing could also be established by correct dimensioning and adding sufficient fixation points between the mating surfaces. Moreover, a separate clamping element may be used to press the mating surfaces together.

The electrical components <NUM> in the electric box <NUM> need to be connected to some of the components of the refrigerant circuit contained in the external housing <NUM>. For this purpose, the electric box <NUM> has either an open bottom or an opening is provided in the bottom <NUM>. A first electric wire <NUM> connected to a first electric component in the electric box <NUM> leaves the electric box through the bottom end of the electric box <NUM> and is connected to the first electric component such as the solenoid valve <NUM> (see <FIG> and <FIG>). For this purpose, the electric wire <NUM> schematically indicated in <FIG> is guided from the bottom <NUM> to the bottom <NUM> of the external housing <NUM>, along the bottom <NUM> and from the bottom <NUM> to the first electric component (in the example the valve <NUM>).

Under some circumstances and for EMC (electromagnetic compatibility) reasons, some electric wires need to be separated from other electric wires. Accordingly, it is conceivable that a second electric wire <NUM> leaves the electric box <NUM> through an opening <NUM> (see <FIG>) between the bottom <NUM> and the top <NUM> of the electric box <NUM>. Also the second electric wire <NUM> is guided to the bottom <NUM> of the external housing <NUM> and from the bottom to the component such as the compressor <NUM>. Neither the first electric wire <NUM> nor the second electric wire <NUM> is fixed to the bottom <NUM> of the external housing <NUM> in the example.

In the case that maintenance of electric components <NUM> or refrigerant components or the fan <NUM> of the electric box <NUM> is required, one has to remove a maintenance wall <NUM> of the external housing <NUM> (see <FIG>). For this purpose, the bolts <NUM> are removed and subsequently the maintenance wall <NUM> can be removed as shown in <FIG>. Once the maintenance wall <NUM> has been removed, one can loosen the bolts <NUM> at the top end of the electric box <NUM> (<FIG>) and pivot the electric box <NUM> about the axis of rotation <NUM>, formed by the bosses <NUM>, out through the opening created by removing the maintenance wall <NUM>. During this process, the boss <NUM> moves from the lower section <NUM> of the engagement portion <NUM> of the slot <NUM> into the upper section <NUM> of the engagement portion <NUM> of the slot <NUM>. Accordingly, the electric box <NUM> is reliably held in the slot <NUM> and can easily be pivoted.

As will be apparent from the above description, the electric box <NUM> and the cooling heat exchanger <NUM> are independently fixed to the support structure <NUM> (the frame <NUM>). There is no attachment of the electric box <NUM> to the cooling heat exchanger <NUM>. Accordingly, moving the electric box <NUM> into the maintenance position (not shown) does not affect the cooling heat exchanger <NUM> and its refrigerant piping <NUM>. The cooling heat exchanger <NUM>, the duct <NUM> (if present) and the sealing <NUM> remain mounted in their position on the frame <NUM> and are not moved together with the electric box <NUM>. In this context, the fan <NUM> may as well be fixed to the electric box <NUM> and may be pivoted into the maintenance position together with the electric box <NUM> to enable easy maintenance or substitution of a damaged fan <NUM>.

When the electric box <NUM> is moved into the maintenance position, the first electric wire <NUM> guided through the bottom <NUM> of the electric box <NUM> moves towards the inner side of the external housing <NUM> and, therefore, in a direction toward the electrical component <NUM> to which it is connected. Accordingly, no strain is applied to the first electric wire <NUM> by moving the electric box <NUM> into the maintenance position.

The second electric wire <NUM> leaving the electric box through the opening <NUM> is first guided to the bottom <NUM> of the external housing <NUM>. Thus, there is a certain free length of the second electric wire <NUM> between the opening <NUM> and the connection to the compressor <NUM>. Thus, also in this case strain on the second electric wire <NUM> can be avoided when moving the electric box <NUM> into the maintenance position.

The above configuration enables easy access to the electric box and does not require any disassembly/assembly work on the cooling heat exchanger <NUM> and it is refrigerant piping <NUM>. For this reason, damages to the cooling heat exchanger <NUM> and its refrigerant piping <NUM> can be prevented.

After the maintenance, the electric box <NUM> is pivoted about the axis of rotation <NUM> (bosses <NUM>) in an opposite direction (clockwise in <FIG> and <FIG>) into the use position shown in the drawings. During this process, the boss <NUM> again moves back to the lower section <NUM> of the engagement portion <NUM> of the slot <NUM> so that the electric box <NUM> is securely supported in a vertical direction. Because the center of gravity <NUM> is closer to a plane <NUM> formed by the contact surface of the sealing <NUM> than to the axis of rotation <NUM> (bosses <NUM>) in a side view, the weight of the electric box <NUM> ensures that the electric box <NUM> is securely pressed against the contact surface of the sealing <NUM> and does even without the bolts <NUM> not "drop" out of the maintenance opening. Subsequently, the bolts <NUM> are reinserted and the maintenance wall <NUM> is reinstalled.

Further, a controller <NUM> is provided which is schematically shown in <FIG>. The controller <NUM> has the purpose of controlling the air conditioner <NUM> and particularly the refrigerant circuit. The controller <NUM> may be accommodated in the electric box <NUM>.

The controller <NUM> may be configured to control the air conditioner <NUM> on the basis of parameters obtained from different sensors.

For example, a first temperature sensor <NUM> is disposed in the interior <NUM> of the external housing <NUM>. Thus, the first temperature sensor <NUM> detects the temperature in the interior <NUM> of the external housing <NUM>. In this context, the position of the first temperature sensor <NUM> is determined relative to the position of the other components in the external casing at a position in which a relatively stable and representative temperature can be measured. Thus, this position has to be determined by experiments.

A second temperature sensor <NUM> may be arranged in the installation room <NUM> in which the heat source unit <NUM> is installed. The second temperature sensor <NUM>, hence, measures a temperature in the installation room <NUM> in other words the temperature of the environment (exterior) of the external housing <NUM>.

Another parameter used by the controller <NUM> is a thermistor <NUM> (third temperature sensor) at an exit line <NUM> between the cooling heat exchanger <NUM> and a suction side of the compressor <NUM> (see <FIG>). In one embodiment, it is conceivable that an accumulator <NUM> is disposed in the line between the cooling heat exchanger <NUM> and the inlet of the compressor <NUM> (suction side). In general, the exit line <NUM> is to be understood as that line connecting the cooling heat exchanger <NUM> to the gas suction line <NUM>, i.e. between an exit of the cooling heat exchanger <NUM> and the connection of the bypass line <NUM> to the gas suction line <NUM>. The thermistor <NUM> measures the temperature of the refrigerant in the exit line <NUM>. Further, a pressure sensor <NUM> is provided and configured to measure the pressure of the refrigerant in the gas suction line <NUM>.

The operation of the air conditioner with respect to the cooling heat exchanger <NUM> is described in more detail below. This operation may also be referred to as the zero heat dissipation control (ZED = zero energy dissipation).

In principle, one can choose between three settings explained in more detail and shown in the table below.

In setting "<NUM>", the valve <NUM> is completely closed and no refrigerant flows through the cooling heat exchanger <NUM>. In this setting, the electric components <NUM> may still be cooled by operating the fan but the heat is dissipated to the interior <NUM> of the external casing <NUM>, and hence the external casing <NUM> and the heat source unit <NUM> dissipate heat to the installation room <NUM>. The zero heat dissipation control is switched OFF.

If setting "<NUM>" is selected, zero heat dissipation control is ON. Yet, in this setting, the cooling capacity of the air conditioner has priority over the zero heat dissipation control. In particular, if a temperature measured in a room <NUM> to be conditioned exceeds a set temperature of the air conditioner in that room <NUM> by a certain value, and the air conditioner can only satisfy this additional cooling demand if the zero heat dissipation control is deactivated, the valve <NUM> will be closed. To put it differently, the valve <NUM> is closed, when a required cooling capacity of the air conditioner exceeds a predetermined threshold. For example, a heat source heat exchanger <NUM> can transfer a certain amount of heat (further referred to as <NUM>% heat load) to (in this example) water (water circuit <NUM>) at certain operating conditions. During operation with deactivated ZED control, the heat source unit <NUM> can remove heat from the room (<NUM>) in correspondence with <NUM>% heat load (cooling operation). Assuming that the heat loss from the electronic components and hot refrigerant components corresponds to <NUM>% of the total heat load, only <NUM>% of heat load (cooling capacity) can be used to cool the room <NUM> during cooling operation. If the above setting is activated, the ZED control can be deactivated resulting in a <NUM>% available capacity to cool the room <NUM>. During heating operation of the room <NUM>, the heat source heat exchanger <NUM> will subtract <NUM>% of heat from the water in the water circuit <NUM> and deliver this heat, together with the <NUM>% heat loss from the electric components <NUM>, to the room <NUM>. This results in a heating capacity of <NUM>%, whereby the heating performance of the air conditioner <NUM> is increased.

If setting "<NUM>" is selected, zero heat dissipation control is ON independent of the cooling capacity of the air conditioner. However, under a certain special control operations, such as start-up and oil return, zero heat dissipation control is still deactivated (the valve <NUM> is closed) in order to avoid damaging of the compressor <NUM> due to liquid refrigerant flowing back into the compressor <NUM>. During start - up mode for example, the rotational speed of the compressor increases to nominal speed. At a low rotational speed, the circulated refrigerant amount is low. Yet, if the distance between the heat source unit <NUM> and the indoor unit <NUM> is large, the refrigerant in the liquid line connecting the heat source unit <NUM> and the indoor unit <NUM> has a relatively high inertia. In contrast, the bypass line <NUM> is relatively short and has a low inertia. As a consequence, a higher proportion of the refrigerant flows through the bypass line <NUM>, whereas a reduced amount or even no refrigerant may flow to the indoor unit <NUM>. This may result in lower comfort in the room <NUM> in which the indoor unit <NUM> is mounted. This may be prevented by closing the valve <NUM>. During oil return operation, a high mass flow rate is generated to flush oil out of the refrigerant circuit components. If the valve <NUM> is open, the mass flow rate through the refrigerant circuit component was reduced resulting in a decreased oil return efficiency.

In either case, the zero heat dissipation control may be performed on the basis of different parameters.

According to a first possibility, the temperature of the interior <NUM> of the external casing <NUM> is measured by the first temperature sensor <NUM> and the controller <NUM> controls the valve <NUM> on the basis of the temperature measured by the first temperature sensor <NUM>.

In particular, the controller <NUM> compares the temperature measured by the first temperature sensor <NUM> with a predetermined temperature. In this embodiment, it is preferred that one either freely inputs the predetermined temperature or can select from different settings as shown in the table below to define the predetermined temperature.

Further, one either freely inputs a differential temperature or again selects the differential temperature from different settings as shown in the table below to define the differential temperature.

According to this control, the controller <NUM> compares the temperature measured by the first temperature sensor <NUM> with the predetermined temperature. If the temperature measured by the first temperature sensor <NUM> exceeds the predetermined temperature, the controller <NUM> is configured to activate the zero heat dissipation control and open the valve <NUM> (completely).

Then again and as shown in <FIG>, if the temperature measured by the first temperature sensor <NUM> falls below the predetermined temperature minus the selected differential temperature, the controller <NUM> is configured to deactivate the zero heat dissipation control and close the valve <NUM> (completely).

For example, if the setting "<NUM>" is selected for the predetermined temperature, the predetermined temperature is <NUM>. Further, if the setting "<NUM>" is selected for the differential temperature, the differential temperature is <NUM>. If for example the temperature measured by the first temperature sensor <NUM> in the interior <NUM> of the external housing <NUM> exceeds <NUM>, the valve <NUM> is opened by the controller <NUM>. Accordingly, the refrigerant flows through the capillary <NUM>, is expanded and then flows into the cooling heat exchanger <NUM>. In the cooling heat exchanger, the refrigerant extracts heat from the air flow <NUM> by heat exchange, whereby the air flow <NUM> is cooled and cooled air is expelled into the interior <NUM> of the external housing <NUM>. Thereby also the hot refrigerant components such as the compressor <NUM>, the liquid receiver <NUM> and the oil separator <NUM> are cooled, because of the orientation of the air outlet <NUM> of the cooling heat exchanger <NUM> in an angled fashion. In particular, the cooled air flow <NUM> is directed in a direction of the hot refrigerant components which are accordingly cooled. In any case, air that is cooler than the air in the interior <NUM> of the external housing <NUM> is expelled from the cooling heat exchanger <NUM> into the interior <NUM>. As a result, the temperature decreases in the external housing <NUM>. Once the temperature measured by the first temperature sensor <NUM> falls below <NUM> (<NUM> - <NUM>), the controller <NUM> closes the valve <NUM> and no refrigerant flows through the cooling heat exchanger <NUM>. This process is repeated as shown in <FIG>.

Alternatively or in addition to the above control, it is also conceivable to use a second temperature sensor <NUM> disposed in the installation room <NUM> and measuring the temperature in the installation room <NUM> to control the valve <NUM>.

In this context, it is conceivable that the zero heat dissipation control is activated (the valve <NUM> is opened) if the temperature detected by the first temperature sensor <NUM> is higher than the temperature measured by the second temperature sensor <NUM>. For example, it may be that the controller <NUM> overrides the above control related to the <NUM>st temperature sensor <NUM>, if the temperature measured by the second temperature sensor <NUM> is lower than the temperature detected by the first temperature sensor <NUM> and closes the valve <NUM> despite the fact that the temperature measured by the first temperature sensor <NUM> is higher than the predetermined temperature.

An even further possibility is that instead of using the first temperature sensor <NUM> to merely use the second temperature sensor <NUM> and control the valve <NUM> on the basis of a comparison between the temperature measured by the second temperature sensor <NUM> and a predetermined temperature in the same manner as explained above with respect to the first temperature sensor <NUM>.

According to a first example, it may be sufficient to compare the predetermined temperature and the temperature measured by the second temperature sensor <NUM> and if the temperature of the second temperature sensor <NUM> exceeds the selected predetermined temperature, the valve <NUM> is opened to activate the zero heat dissipation control. Subsequently, if the temperature measured by the second temperature sensor <NUM> falls below the predetermined temperature minus the differential temperature, the valve <NUM> is again closed.

According to a second example, it is as well conceivable to define a second differential temperature in the same manner as the first differential temperature. If the temperature measured by the second temperature sensor <NUM> is higher than the predetermined temperature and the delta between the temperature measured by the second temperature sensor <NUM> and the predetermined temperature is higher than the second differential temperature, the valve <NUM> is opened. In the same manner as described above, if the temperature measured by the second temperature sensor <NUM> falls below the predetermined temperature by the first differential temperature, the valve <NUM> is closed and the zero heat dissipation control is deactivated.

An even further control mechanism to activate/deactivate the zero heat dissipation control (open/close the valve <NUM>) may be based on the thermistor <NUM> disposed at the exit line <NUM> and particularly the temperature of the refrigerant in the exit line <NUM> measured by the thermistor <NUM>. Further, the controller <NUM> uses the pressure measured by the pressure sensor <NUM> disposed at the gas suction line <NUM>. In particular, the controller <NUM> concludes on the two-phase temperature (the temperature at which a phase change from liquid to gas takes place) on the basis of the pressure measured by the pressure sensor is <NUM>. Subsequently, the controller <NUM> compares this two-phase temperature and the temperature measured by the thermistor <NUM>. If the temperature measured by the thermistor <NUM> is higher than the two-phase temperature, it is concluded that superheated gaseous refrigerant leaves the cooling heat exchanger <NUM>. The output of the thermistor <NUM> is, hence, used by the controller <NUM> to conclude or calculate on the basis of a pressure in the gas suction line <NUM> and the temperature at an outlet of the cooling heat exchanger <NUM> (cooling heat exchanger gas outlet) on a superheat degree. Subsequently, and depending on the superheat degree open or close the valve <NUM>. This control is particularly a safety measure to prevent liquid refrigerant from remaining in the exit line <NUM> and/or being pumped into the accumulator <NUM> (if present) or the compressor <NUM>. In particular, the controller <NUM> is configured to switch to the OFF-mode of the valve <NUM>, when the calculated superheat degree falls below a predetermined value for a predetermined period of time. During operation, the pressure difference between the liquid line <NUM> and the gas suction line <NUM> will depend on the operational conditions of the heat source unit <NUM>. If there is a pressure drop in the bypass line <NUM>, a refrigerant flow may be induced from the gas suction line <NUM> into the bypass line <NUM>. Depending on the air temperature in the external housing <NUM>, the refrigerant flowing through the cooling heat exchanger <NUM> and the thermal capacity of the air may be out of balance resulting in a fully evaporated refrigerant with a possible high superheat or a not fully evaporated refrigerant which contains liquid refrigerant. Those extreme situations may be avoided by opening/closing the valve <NUM> on the basis of the superheat degree obtained via the thermistor.

Claim 1:
Heat source unit (<NUM>) for an air conditioner (<NUM>) comprising a refrigerant circuit, the heat source unit comprising:
an external housing (<NUM>) accommodating:
a compressor (<NUM>) to be connected to the refrigerant circuit;
a heat source heat exchanger (<NUM>) to be connected to the refrigerant circuit and configured to exchange heat between a refrigerant circulating in the refrigerant circuit and a heat source (<NUM>);
an electric box (<NUM>) having a top (<NUM>) and side walls (<NUM> to <NUM>), the electric box accommodating electrical components (<NUM>) configured to control the air conditioner and having an air passage (<NUM>) comprising an air inlet (<NUM>) and an air outlet (<NUM>), an air flow (<NUM>) being induced through the air passage from the air inlet to the air outlet for cooling at least some of the electrical components,
characterized by
a cooling heat exchanger (<NUM>) accommodated in the external housing and to be connected to the refrigerant circuit, wherein the cooling heat exchanger (<NUM>) is arranged at one of the side walls (<NUM> to <NUM>) of the electric box so as to be flown through by the air flow (<NUM>) and exchange heat between the refrigerant and the air flow (<NUM>).