EP2532981A2

EP2532981A2 - Water Supply Apparatus

Info

Publication number: EP2532981A2
Application number: EP12169940A
Authority: EP
Inventors: Sung Goo Kim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2011-06-10
Filing date: 2012-05-30
Publication date: 2012-12-12
Also published as: KR20120136854A; US20120312045A1; CN102818308A; CN102818308B; EP2532981A3

Abstract

Disclosed herein is a water supply apparatus which may include an outdoor unit installed outdoors, and a cascade unit to receive refrigerant from the outdoor unit and generate hot water of a first temperature and/or hot water of a second temperature higher than the first temperature. The water supply apparatus may generate hot water of the first temperature, hot water of the second temperature higher than the first temperature and/or cold water.

Description

The present invention relates to a water supply apparatus to supply cold water and/or hot water using a refrigeration cycle.
Generally, a water supply apparatus may be an apparatus which heats water supplied from an external water supply source to generate hot water and supplies the generated hot water to a water consumption unit such as a radiator or boiler for warming. Recently, some water supply apparatuses may include refrigeration cycle components including a compressor, a condenser, an expansion valve, evaporator, etc. and thus supply both hot water and cold water by heating and/or cooling water using a refrigeration cycle.
In an aspect of one or more embodiments, there is provided a water supply apparatus which may generate hot water with a first temperature and/or hot water with a second temperature higher than the first temperature.
In accordance with an aspect of one or more embodiments, there is provided a water supply apparatus may include an outdoor unit installed outdoors, and a cascade unit to receive refrigerant from the outdoor unit and generate hot water with a first temperature and/or hot water with a second temperature higher than the first temperature.
The outdoor unit may include a first compressor to compress a first refrigerant and a first heat exchanger to enable the first refrigerant to exchange heat with outdoor air.
The cascade unit may include a second compressor to compress a second refrigerant, a second heat exchanger to enable water supplied from an external water supply source to exchange heat with the first refrigerant transferred from the outdoor unit, a third heat exchanger to enable the second refrigerant to be suctioned into the second compressor to be heated by the first refrigerant transferred from the outdoor unit, and a fourth heat exchanger to enable water supplied from the external water supply source to exchange heat with the second refrigerant discharged from the second compressor. The apparatus may further include a 4-way valve disposed at a discharge side of the first compressor, a first refrigerant pipe having one end connected to the first compressor, a second refrigerant pipe having one end connected to the first heat exchanger, a first connection refrigerant pipe having one end connected to the 4-way valve and the other end connected to the first heat exchanger, a first branched refrigerant pipe branched from the other end of the first refrigerant pipe and connected to the second heat exchanger, a second branched refrigerant pipe branched from the other end of the first refrigerant pipe and connected to the third heat exchanger, a third branched refrigerant pipe branched from the other end of the second refrigerant pipe and connected to the second heat exchanger, a fourth branched refrigerant pipe branched from the other end of the second refrigerant pipe and connected to the third heat exchanger, a first 3-way valve to enable the first refrigerant pipe to communicate with any one of the first branched refrigerant pipe and the second branched refrigerant pipe, a first expansion valve disposed at the third branched refrigerant pipe, and a second expansion valve disposed at the fourth branched refrigerant pipe.
The apparatus may further include a second discharged refrigerant pipe to guide the second refrigerant discharged from the second compressor to the fourth heat exchanger, a second suctioned refrigerant pipe to guide the second refrigerant from the third heat exchanger to be suctioned into the second compressor, a second connection refrigerant pipe to connect the third heat exchanger and the fourth heat exchanger to each other, and a third expansion valve disposed at the second connection refrigerant pipe.
The apparatus may further include a first water pipe supplied with water from the external water supply source, a second water pipe branched from the first water pipe to guide water to the second heat exchanger, a third water pipe branched from the first water pipe to guide water to the fourth heat exchanger, a fourth water pipe to connect to a water consumption apparatus, a fifth water pipe to guide water passing through the second heat exchanger to the fourth water pipe, a sixth water pipe to guide water passing through the fourth heat exchanger to the fourth water pipe, and a second 3-way valve disposed between the first water pipe and the second water pipe and the third water pipe so as to enable water from the first water pipe to be supplied to any one of the second and third water pipes.
The apparatus may further include a pump disposed at the fourth water pipe to enable water to be suctioned from the external water supply source and be discharged to the water consumption apparatus.
In accordance with an aspect of one or more embodiments, there is provided a water supply apparatus may include a first compressor to compress first refrigerant, a first heat exchanger to enable the first refrigerant to exchange heat with outdoor air, a second compressor to compress second refrigerant, a second heat exchanger to enable water supplied from an external water supply source to exchange heat with the first refrigerant, a third heat exchanger to enable the second refrigerant to be suctioned into the second compressor to be heated by the first refrigerant, and a fourth heat exchanger to enable water supplied from the external water supply source to exchange heat with the second refrigerant discharged from the second compressor.
The apparatus may include an outdoor unit disposed outdoors which includes the first compressor and first heat exchanger, and a cascade unit including the second compressor and the second, third and fourth heat exchangers.
The outdoor unit and the cascade unit may be formed as individual units and may be connected to each other via a refrigerant pipe.
The outdoor unit may include the cascade unit.
In an aspect of one or more embodiments, there is provided a water supply apparatus which may generate hot water with a first temperature and/or hot water with a second temperature higher than the first temperature and hence may more efficiently supply hot water of a desired temperature.
These and/or other aspects will become apparent and more readily appreciated from the following description of embodiments, taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic view illustrating a case in which hot water of a first temperature is generated by a water supply apparatus according to an embodiment;
FIG. 2 is a schematic view illustrating a case in which hot water of a second temperature higher than the first temperature is generated by a water supply apparatus according to an embodiment;
FIG. 3 is a schematic view illustrating a case in which cold water is supplied by a water supply apparatus according to an embodiment; and
FIG. 4 is a schematic view of a water supply apparatus according to an embodiment.

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.
Below, a water supply apparatus according to an embodiment will be described in detail with reference to the accompanying drawings.
As shown in FIG. 1, a water supply apparatus according to an embodiment cools or heats water transferred from an external water supply source 30 to generate cold water or hot water and supplies the cold water or hot water into a water consumption apparatus 40.
The water supply apparatus includes an outdoor unit 10 installed outdoors to exchange heat with outdoor air and a cascade unit 20 to receive first refrigerant from the outdoor unit 10 and generate cold water and hot water. In an embodiment, the cascade unit 20 is configured to generate cold water, hot water with a first temperature and/or hot water with a second temperature higher than the first temperature.
The outdoor unit 10 includes a first compressor 11 to compress the first refrigerant, a 4-way valve 14 installed at a discharge side of the first compressor 11 to enable selection of cold water generation or hot water generation, a first heat exchanger 12 to enable the first refrigerant to exchange heat with outdoor air, and a blowing fan 13 to enable outdoor air to pass through the first heat exchanger 12 and exchange heat with the first refrigerant.
The cascade unit 20 includes a second compressor 21 to compress a second refrigerant, a second heat exchanger 22 to enable the first refrigerant transferred from the outdoor unit 10 to exchange heat with water, and a third heat exchanger 23 to enable the second refrigerant to be suctioned into the second compressor 21 to exchange heat with the first refrigerant transferred from the outdoor unit 10 so that the second refrigerant to be suctioned into the second compressor 21 is heated by the first refrigerant transferred from the outdoor unit 10. The cascade unit 20 further includes a fourth heat exchanger 24 to enable water supplied from the external water supply source 30 to exchange heat with the second refrigerant discharged from the second compressor 21.
The above-mentioned components may be connected to one another via a plurality of refrigerant pipes to transfer the first and second refrigerants.
The refrigerant pipes to transfer the first refrigerant may include a first refrigerant pipe RP1 having one end connected to the first compressor 11, a second refrigerant pipe RP2 having one end connected to the first heat exchanger 12, a first branched refrigerant pipe RP1-1 branched from the other end of the first refrigerant pipe RP1 and connected to the second heat exchanger 22, a second branched refrigerant pipe RP1-2 branched from the other end of the first refrigerant pipe RP1 and connected to the third heat exchanger 23, a third branched refrigerant pipe RP2-1 branched from the other end of the second refrigerant pipe RP2 and connected to the second heat exchanger 22, a fourth branched refrigerant pipe RP2-2 branched from the other end of the second refrigerant pipe RP2 and connected to the third heat exchanger 23, a first discharged refrigerant pipe RP3 to guide the first refrigerant discharged from the first compressor 11 to the 4-way valve 14, a first suctioned refrigerant pipe RP4 to guide the first refrigerant to be suctioned into the first compressor 11, and a first connection refrigerant pipe RP5 to connect the 4-way valve 14 and the first heat exchanger 12 to each other.
The refrigerant pipes to transfer the second refrigerant may include a second discharged refrigerant pipe RP6 to guide the second refrigerant discharged from the second compressor 21 to a fourth heat exchanger 24, a second suctioned refrigerant pipe RP7 to guide the second refrigerant from the third heat exchanger 23 to be suctioned into the second compressor 21, and a second connection refrigerant pipe RP8 to connect the third heat exchanger 23 and the fourth heat exchanger 24 to each other.
In this configuration, a first 3-way valve V1 is disposed between the other end of the first refrigerant pipe RP1 and the first branched refrigerant pipe RP1-1 and the second branched refrigerant pipe RP1-2 so as to enable the first refrigerant pipe RP1 to communicate with a selected one of the first branched refrigerant pipe RP1-1 and the second branched refrigerant pipe RP1-2.
The cascade unit 20 further includes a plurality of expansion valves to expand the refrigerant in a depressurized manner. Such expansion valves include a first expansion valve 25 disposed at the third branched refrigerant pipe RP2-1, a second expansion valve 26 disposed at the fourth branched refrigerant pipe RP2-2, and a third expansion valve 27 disposed at the second connection refrigerant pipe RP8.
The cascade unit 20 further includes a plurality of water pipes constructed to allow water supplied from the external water supply source 30 to pass through the cascade unit 20 while being heated or cooled. Such water pipes include a first water pipe WP1 supplied with water from the external water supply source 30, a second water pipe WP2 branched from the first water pipe WP1 to guide water to the second heat exchanger 22, a third water pipe WP3 branched from the first water pipe WP1 to guide water to the fourth heat exchanger 24, a fourth water pipe WP4 to connect to the water consumption apparatus 40, a fifth water pipe WP5 to guide water passing through the second heat exchanger 22 to the fourth water pipe WP4, and a sixth water pipe WP6 to guide water passing through the fourth heat exchanger 24 to the fourth water pipe WP4.
In this configuration, a second 3-way valve V2 is disposed between the first water pipe WP1 and the second water pipe WP2 and the third water pipe WP3 so as to enable water from the first water pipe WP1 to be supplied to a selected one of the second and third water pipes WP2 and WP3. At the fourth water pipe WP4, there is disposed a pump 28 to enable water supplied from the external water supply source 30 and then passing through any one of the second and fourth heat exchangers 22 and 24 to be discharged to the water consumption apparatus 40.
Below, a case in which hot water of a first temperature is generated using the water supply apparatus according to an embodiment will be described with reference to FIG. 1.
The first refrigerant with a high temperature discharged from the first compressor 11 passes through the first discharged refrigerant pipe RP3, the 4-way valve 14, the first refrigerant pipe RP1, the first 3-way valve V1 and the first branched refrigerant pipe RP1-1 in this order and is transferred to the second heat exchanger 22. Meantime, water supplied from the external water supply source 30 passes through, using the pump 28, the first water pipe WP1, the second 3-way valve V2 and the second water pipe WP2 in this order and is transferred to the second heat exchanger 22. Thus, the water supplied from the external water supply source 30 and the first refrigerant with a high temperature transferred from the outdoor unit 10 may exchange heat with each other. At this time, since the first refrigerant compressed by the first compressor 11 so as to have a relatively higher temperature than that of the water from the external water supply source 30 may be transferred to the second heat exchanger 22, the water may be heated by the first refrigerant to become hot water with a first temperature while the first refrigerant may be cooled and condensed by the water.
The hot water with the first temperature generated from the second heat exchanger 22 passes through the fifth water pipe WP5, the pump 28 and the fourth water pipe WP4 in this order and is transferred to the water consumption apparatus 40. The first temperature of the hot water acquired by this process may be at most 55 °C.
The first refrigerant cooled and condensed by the water passes through the third branched refrigerant pipe RP2-1 while being expanded in a depressurized manner through the first expansion valve 25 provided at the third branched refrigerant pipe RP2-1. Then, the expanded first refrigerant is transferred through the second refrigerant pipe RP2 to the first heat exchanger 12 in which the first refrigerant is evaporated to absorb heat from outdoor air. The evaporated first refrigerant from the first heat exchanger 12 passes through the first connection refrigerant pipe RP5 and the 4-way valve 14 and the first suctioned refrigerant pipe RP4 in this order and then is transferred again to the first compressor 11.
Hereinafter, a case in which hot water of a second temperature is generated using the water supply apparatus according to an embodiment will be described with reference to FIG. 2.
The first refrigerant with a high temperature discharged from the first compressor 11 passes through the first discharged refrigerant pipe RP3, the 4-way valve 14, the first refrigerant pipe RP1, the first 3-way valve V1 and the second branched refrigerant pipe RP1-2 in this order and is transferred to the third heat exchanger 23. The second refrigerant discharged from the second compressor 21 passes through the fourth heat exchanger 24 while being cooled and condensed as will be described later and thereafter passes through the second connection refrigerant pipe RP8 and the third expansion valve 27 provided at the second connection refrigerant pipe RP8 and then is transferred to the third heat exchanger 23.
Water supplied from the external water supply source 30 passes through, using the pump 28, the first water pipe WP1, the second 3-way valve V2 and the third water pipe WP3 in this order and is transferred to the fourth heat exchanger 24. As mentioned above, in the fourth heat exchanger 24, the water cools and condenses the second refrigerant discharged from the second compressor 21.
Thus, in the third heat exchanger 23, the first refrigerant transferred from the outdoor unit 10 and the second refrigerant expanded in a depressurized manner using the third expansion valve 27 exchange heat with each other. At this time, because the first refrigerant transferred from the outdoor unit 10 is transferred to the third heat exchanger 23 in a high temperature state resulting from compression of the first compressor 11 while the second refrigerant is transferred to the third heat exchanger 23 in an expanded and depressurized state resulting from operation of the third expansion valve 27, the second refrigerant may be heated and evaporated by the first refrigerant whereas the first refrigerant may be cooled and condensed by the second refrigerant.
As mentioned above, water supplied from the external water supply source 30 passes through, using the pump 28, the first water pipe WP1, the second 3-way valve V2 and the third water pipe WP3 in this order and is transferred to the fourth heat exchanger 24. In the fourth heat exchanger 24, the water supplied from the external water supply source 30 and the second refrigerant discharged from the second compressor 21 exchange heat with each other. At this time, since the second refrigerant is transferred to the fourth heat exchanger 24 in a relatively higher temperature state than that of the water, the water may be heated by the second refrigerant whereas the second refrigerant may be cooled and condensed by the water.
Further, at this time, since the second refrigerant transferred to the fourth heat exchanger 24 is heated by the first refrigerant transferred from the outdoor unit 10 and thereafter is again compressed by the second compressor 21, the second refrigerant transferred to the fourth heat exchanger 24 from the second compressor 21 may heat the water transferred to the fourth heat exchanger 24 to the temperature relatively higher than the first temperature. That is, in the fourth heat exchanger 24, the water may be heated by the second refrigerant to become hot water having the second temperature relatively higher than the first temperature.
The hot water with the second temperature generated from the fourth heat exchanger 24 passes through the sixth water pipe WP6, the pump 28 and the fourth water pipe WP4 in this order and is transferred to the water consumption apparatus 40. The second temperature of the hot water acquired by this process may be at most 85 °C.
The second refrigerant evaporated at the third heat exchanger 23 is transferred again to the second compressor 21 through the second suctioned refrigerant pipe RP7.
The first refrigerant cooled and condensed at the third heat exchanger 23 passes through the fourth branched refrigerant pipe RP2-2 while being expanded in a depressurized manner through the second expansion valve 26 provided at the fourth branched refrigerant pipe RP2-2. Then, the expanded first refrigerant is transferred through the second refrigerant pipe RP2 to the first heat exchanger 12 in which the first refrigerant is evaporated to absorb heat from outdoor air. The evaporated first refrigerant from the first heat exchanger 12 passes through the first connection refrigerant pipe RP5 and the 4-way valve 14 and the first suctioned refrigerant pipe RP5 in this order and then is transferred again to the first compressor 11.
Hereinafter, a case in which cold water is generated using the water supply apparatus according to an embodiment will be described with reference to FIG. 3.
The first refrigerant with a high temperature discharged from the first compressor 11 passes through the first discharged refrigerant pipe RP3, the 4-way valve 14, and the first connection refrigerant pipe RP3 in this order and is transferred to the first heat exchanger 12. This condensed second refrigerant passes through the second refrigerant pipe RP2 and the third branched refrigerant pipe RP2-1 while being expanded in a depressurized manner through the first expansion valve 25 provided at the third branched refrigerant pipe RP2-1 and then is transferred to the second heat exchanger 22. Water supplied from the external water supply source 30 passes through, using the pump 28, the first water pipe WP1, the second 3-way valve V2 and the second water pipe WP2 in this order and is transferred to the second heat exchanger 22.
Since a depressurized and expanded refrigerant readily absorbs heat, the depressurized and expanded first refrigerant may absorb heat from the water to be evaporated while the water may be cooled to become cold water in the second heat exchanger 22.
The cold water generated from the second heat exchanger 22 passes through the fifth water pipe WP5, the pump 28 and the fourth water pipe WP4 in this order and is transferred to the water consumption apparatus 40. The temperature of the cold water acquired by this process may be at least 5 °C.
Meantime, the first refrigerant evaporated by absorbing heat from the water passes through the third branched refrigerant pipe RP2-1, the first expansion valve 25 provided at the third branched refrigerant pipe RP2-1, the first branched refrigerant pipe RP1-1, the first 3-way valve V1, the first refrigerant pipe RP1, the 4-way valve 14 and the first suctioned refrigerant pipe RP4 in this order and then is transferred again to the first compressor 11.
In winter, frost may occur on the first heat exchanger 121 provided in the outdoor unit 10 in the course of generating hot water with the first or second temperature as mentioned above. At this case, heat exchange rate between the first refrigerant and outdoor air may be reduced, thereby deteriorating performance of the water supply apparatus.
For this reason, the water supply apparatus is controlled to defrost the first heat exchanger 12. More specifically, the 4-way valve 14 is controlled to guide the first refrigerant with a high temperature discharged from the first compressor 11 to the first heat exchanger 11. In this way, by guiding the first refrigerant with a high temperature discharged from the first compressor 11 to the first heat exchanger 11, the first heat exchanger 11 may be defrosted using heat of the first refrigerant.
In the course of the above defrosting treatment, if the water supplied from the external water supply source 30 has a temperature above a predetermined temperature, the first refrigerant passing through the first heat exchanger 12 may be transferred to the second heat exchanger 12. In this way, the first refrigerant may absorb heat from the water having the temperature above the predetermined temperature and thus emits more heat to the first heat exchanger 12, resulting in rapid completion of the defrosting of the first heat exchanger 12. Moreover, since the temperature of the water is above the predetermined temperature as described above, the water is not prevented from being frozen although heat of the water is absorbed by the first refrigerant.
On the other hand, if water supplied from the external water supply source 30 has a temperature below a predetermined temperature, the water may be frozen when the first refrigerant absorbs heat of the water, leading to a damage of the water pipes. For this reason, when the temperature of water supplied from the external water supply source is below the predetermined temperature, the first refrigerant passing through the first heat exchanger 12 is transferred to the third heat exchanger 23 to exchange heat with the second refrigerant. In this situation, because a temperature of the second refrigerant may not be particularly high, the first refrigerant may absorb small amount of heat from the water. Therefore, it may take a relatively longer time for the first refrigerant to defrost the first heat exchanger 12 than in the case when the first refrigerant absorbs heat from the water. Nevertheless, damage of the water pipes may be prevented because the first refrigerant may not affect the temperature of the water.
The water supply apparatus according to an embodiment, as mentioned above, may selectively generate hot water with a first temperature, hot water with a second temperature relatively higher than the first temperature and/or cold water. At this time, whether to generate hot water with the first temperature or hot water with the second temperature may depend on the outside temperature of the outdoor unit 10, the temperature of water supplied from the external water supply source 30 and the temperature of water discharged to the water consumption unit 40.
In an embodiment, the outdoor unit 10 and the cascade unit 20 are formed as individual units and are connected to each other via a refrigerant pipe. However, embodiments are not limited thereto. Alternatively, as shown in FIG. 4 as an embodiment, the outdoor unit 10 may include the cascade unit 20. That is, the outdoor unit 10 may include the second compressor and heat exchanger 21, 22, the third and fourth heat exchangers 23, 24 and the first, second and third expansion valves 25, 26, 27 which are included in the cascade unit 20.
In an embodiment, the 4-way valve 14 is disposed at the discharge side of the first compressor 11 to selectively enable hot water generation or cold water generation. However, embodiments are not limited thereto. Alternatively, the 4-way valve 14 may be dispensed with and accordingly the cold water generation may be omitted. Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles of the invention, the scope of which is defined in the claims.

Claims

A water supply apparatus comprising:
an outdoor unit installed outdoors; and

a cascade unit to receive refrigerant from the outdoor unit and to generate at least one of hot water of a first temperature and hot water of a second temperature, which is higher than the first temperature.
The apparatus according to claim 1, wherein:
the outdoor unit includes a first compressor to compress first refrigerant and a first heat exchanger to enable the first refrigerant to exchange heat with outdoor air; and

the cascade unit includes a second compressor to compress second refrigerant, a second heat exchanger to enable water supplied from an external water supply source to exchange heat with the first refrigerant transferred from the outdoor unit, a third heat exchanger to enable the second refrigerant to be suctioned into the second compressor to be heated by the first refrigerant transferred from the outdoor unit, and a fourth heat exchanger to enable water supplied from the external water supply source to exchange heat with the second refrigerant discharged from the second compressor.
The apparatus according to claim 2, further comprising:
a 4-way valve disposed at a discharge side of the first compressor;

a first refrigerant pipe having one end connected to the first compressor;

a second refrigerant pipe having one end connected to the first heat exchanger;

a first connection refrigerant pipe having one end connected to the 4-way valve and the other end connected to the first heat exchanger;

a first branched refrigerant pipe branched from the other end of the first refrigerant pipe and connected to the second heat exchanger;

a second branched refrigerant pipe branched from the other end of the first refrigerant pipe and connected to the third heat exchanger;

a third branched refrigerant pipe branched from the other end of the second refrigerant pipe and connected to the second heat exchanger;

a fourth branched refrigerant pipe branched from the other end of the second refrigerant pipe and connected to the third heat exchanger;

a first 3-way valve to enable the first refrigerant pipe to communicate with any one of the first branched refrigerant pipe and the second branched refrigerant pipe;

a first expansion valve disposed at the third branched refrigerant pipe; and

a second expansion valve disposed at the fourth branched refrigerant pipe.
The apparatus according to claim 2, further comprising:
a second discharged refrigerant pipe to guide the second refrigerant discharged from the second compressor to the fourth heat exchanger;

a second suctioned refrigerant pipe to guide the second refrigerant from the third heat exchanger to be suctioned into the second compressor;

a second connection refrigerant pipe to connect the third heat exchanger and the fourth heat exchanger to each other; and

a third expansion valve disposed at the second connection refrigerant pipe.
The apparatus according to claim 2, further comprising:
a first water pipe supplied with water from the external water supply source;

a second water pipe branched from the first water pipe to guide water to the second heat exchanger;

a third water pipe branched from the first water pipe to guide water to the fourth heat exchanger;

a fourth water pipe to connect to a water consumption apparatus;

a fifth water pipe to guide water passing through the second heat exchanger to the fourth water pipe;

a sixth water pipe to guide water passing through the fourth heat exchanger to the fourth water pipe; and

a second 3-way valve disposed between the first water pipe, the second water pipe and the third water pipe so as to enable water from the first water pipe to be supplied to any one of the second and third water pipes.
The apparatus according to claim 5, further comprising a pump disposed at the fourth water pipe to enable water to be suctioned from the external water supply source and be discharged to the water consumption apparatus.
The apparatus according to claim 1, wherein the outdoor unit comprises the cascade unit.
The water supply apparatus of claim 1, wherein the cascade unit generates cold water, hot water of a first temperature and hot water of a second temperature, the second temperature being higher than the first temperature.