Technological background Within the technical field with which the invention is concerned, air-conditioners of the so-called"split"type are known and such an air-conditioner typically comprises a cooling circuit with a motor-driven condenser including a compressor and a condenser, connected to one or more evaporation units which are advantageously arranged in the rooms to be conditioned.

Air-conditioners of this type are also used, amongst other places, in hotels and holiday resorts, where a motor- driven condenser unit may be provided for each room or 9 apartment (or for groups of rooms or apartments) and connected to respective evaporation units installed in the individual rooms to be conditioned.

In the more general field of air-conditioning technology, it is also known to use at least some of the heat given up by a coolant fluid during the condensation stage to produce hot water as a by-product of the main process of conditioning the rooms.

In fact, in large air-conditioning installations in which a single motor-driven condenser unit serves a substantial number of evaporation units, an auxiliary heat exchanger may be connected in the cooling circuit in order to recover heat. In practice, this heat-exchanger puts the water to be heated into thermal contact with the hot coolant fluid output from the compressor.

A main limitation of this type of air-conditioning system with heat recovery is that the production of hot water is inextricably linked with the operation of the cooling circuit as a whole. In particular, it is not possible to produce hot water without simultaneously cooling at least some of the rooms in which the evaporation units are present.

This consequently limits the use of this resource to climatic periods in which such cooling responds to a primary requirement.

Description of the invention The problem upon which the present invention is based is that of providing an air-conditioner with heat recovery which is designed structurally and functionally to overcome the limitations set out above with reference to the prior art mentioned.

This problem is solved by the present invention by means of an air-conditioner with heat recovery, formed in accordance with the appended claims.

Brief description of the drawings The characteristics and the advantages of the invention will become clearer from the detailed description of a preferred embodiment thereof, described by way of non- limiting example with reference to the appended drawings, in which : -Figure 1 is a schematic view of a air-conditioner with heat recovery formed in accordance with the present invention, and -Figure 2 shows schematically the method of operation of the air-conditioner of Figure 1.

Preferred embodiment

With reference to the appended drawings, an air- conditioner with heat recovery formed in accordance with the present invention is generally indicated 1.

The air-conditioner 1 is preferably of the"split"type and comprises a cooling circuit 2 in which a coolant fluid is circulated.

The cooling circuit 2 includes a compressor 3, connected by means of a delivery line 4 to a heat-exchanger 5 and then to a condenser 6.

The heat-exchanger 5 is preferably of the type with plates and is arranged to put the coolant fluid output from the compressor 3 into thermal contact with water for hygiene purposes which circulates in a second circuit 7 and is then advantageously stored in a storage tank 8.

An evaporation unit 9 is provided in the delivery line 4, downstream of the condenser 6, and is advantageously positioned in the room to be conditioned.

The evaporation unit 9 comprises first means 10 for the expansion of the coolant fluid, including, for example a capillary 11, an evaporator 12, and an on-off valve 13 which can exclude the evaporation unit 9 from the cooling circuit 2. The output 14 of the evaporation unit 9 is connected to a return line 15 which in turn is connected to the intake of the compressor 3.

It is intended that the air-conditioner 1 may also comprise further evaporation units 9a, indicated by broken lines in the drawings, positioned in other rooms and suitably connected in parallel with the evaporator unit 9.

First and second by-pass means, indicated 16 and 17, respectively, as well as second expansion means 18 interposed

between the heat-exchanger 5 and the condenser 6, are also provided in the air-conditioner 1.

The first by-pass means 16 is arranged in parallel with the evaporation unit 9 and comprises a first on-off valve 19 which can selectively put the delivery line 4 downstream of the condenser 6 into communication with the return line 15 in order to exclude the evaporation unit 9 from the flow-path of the coolant fluid.

The second by-pass means 17 in turn is arranged in parallel with the second expansion means 18 and comprises a second on-off valve 20 which can selectively put the heat- exchanger 5 into communication with the condenser 6 in order to exclude the second expansion means 18 from the flow-path of the coolant fluid.

The first and second on-off valves 19,20 are controlled by control means 21 which are set to open one or other of the valves alternatively in a mutually exclusive arrangement so that, when one of the two on-off valves is open, the other is necessarily closed.

Two different modes of operation of the air-conditioner 1 are thus defined, according to the selection made by the control means 21.

In the first mode of operation, the first on-off valve 19 is closed and the second on-off valve 20 is open. In this mode, after the hot coolant fluid output from the compressor 3 has given up some of its heat to the water of the second circuit 7 in the heat exchanger 5, it is admitted by means of the second on-off valve 20 to the condenser 6 where it is fully condensed by means of a service fluid, normally external air. Once it has condensed, the coolant fluid is supplied to the evaporation unit 9, where it is first of all

brought to a lower pressure by passing through the first expansion means 10 and is then evaporated in the evaporator 12, correspondingly cooling the surrounding atmosphere.

By operating the control means 21, it is possible to change from the first mode of operation to the second mode in which the first on-off valve 19 is open and the second on-off valve 20 is closed. In this mode, after the coolant fluid has exchanged heat with the water of the second circuit 7, it is brought to a lower pressure by passing through the second expansion means 18 and is then admitted to the condenser 6.

Here, the coolant fluid is in temperature and pressure conditions such as to be evaporated, removing heat from the service fluid (external air). The coolant fluid is then admitted to the return line 15 by means of the first on-off valve 19, without passing through the evaporation unit 9.

It will be noted that, in this second mode of operation, the condenser 6 actually performs the function of an evaporator in the cooling circuit 2. From the energy point of view, this enables heat to be supplied to the water of the second circuit 7 by the removal of heat from the service fluid, rather than from the room in which the evaporation unit 9 is disposed, and the air-conditioner 1 can thus produce hot water without simultaneously having an air- conditioning effect on the room with which it is associated.

The present invention thus solves the problem complained of above with reference to the prior art mentioned, at the same time offering many other advantages, amongst which is the ability to provide, with the air-conditioner, a hot-water producing system which is functionally independent of the system for the air-conditioning of the rooms.

This characteristic is particularly advantageous in applications relating to systems in hotels and holiday resorts, where there is a need, on the one hand, to condition rooms at predetermined times of the year and, on the other hand, to respond to a demand for hot water which is particularly concentrated during predetermined time bands.

The air-conditioners of the present invention enable every room or apartment to be rendered independent with regard to hot-water requirements. The need to provide centralized heating systems of a size suitable for responding to hot-water requirement peaks is thus eliminated, which has an advantageous impact on the costs connected with their installation and maintenance.

A further advantage is that the characteristics of the air-conditioner according to the invention are achieved with low production costs.