U.S. patent application number 14/396126 was filed with the patent office on 2015-03-19 for air conditioning system and defrosting operation method.
This patent application is currently assigned to DAIKIN INDUSTRIES, LTD.. The applicant listed for this patent is DAIKIN INDUSTRIES. LTD.. Invention is credited to Shigekazu Wasa.
Application Number | 20150075192 14/396126 |
Document ID | / |
Family ID | 49514337 |
Filed Date | 2015-03-19 |
United States Patent
Application |
20150075192 |
Kind Code |
A1 |
Wasa; Shigekazu |
March 19, 2015 |
AIR CONDITIONING SYSTEM AND DEFROSTING OPERATION METHOD
Abstract
Temperature sensors detect an outdoor air temperature and a heat
exchanger temperature of an outdoor unit, and a human detection
sensor detects presence of a person in an air blowable region of
each indoor unit. A control section selectively executes a first
defrosting operation mode in which a defrosting operation is
performed while fans of all the indoor units are stopped, and a
second defrosting operation mode in which, when a frost formation
amount in the heat exchanger is estimated to exceed a threshold
value on the basis of the temperatures detected by the first and
second temperature sensors, the indoor unit for which the human
detection sensor detects no person in its air blowable region is
preferentially selected, and a defrosting operation is performed
while the fan of the indoor unit is forcibly operated. Such an air
conditioning system and a defrosting operation method reduce time
required for defrosting.
Inventors: |
Wasa; Shigekazu; (Sakai-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAIKIN INDUSTRIES. LTD. |
Osaka-shi, Osaka |
|
JP |
|
|
Assignee: |
DAIKIN INDUSTRIES, LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
49514337 |
Appl. No.: |
14/396126 |
Filed: |
April 3, 2013 |
PCT Filed: |
April 3, 2013 |
PCT NO: |
PCT/JP2013/060151 |
371 Date: |
October 22, 2014 |
Current U.S.
Class: |
62/80 ;
62/156 |
Current CPC
Class: |
F25B 13/00 20130101;
F25B 47/025 20130101; F24F 2140/20 20180101; F24F 11/77 20180101;
F25D 21/004 20130101; F24F 11/42 20180101; F25B 2313/0315 20130101;
F24F 11/30 20180101; F24F 2110/12 20180101; F25B 2700/2106
20130101; F24F 2120/10 20180101; F25B 2313/0233 20130101; F25B
2313/0293 20130101; Y02B 30/70 20130101 |
Class at
Publication: |
62/80 ;
62/156 |
International
Class: |
F25D 21/00 20060101
F25D021/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 1, 2012 |
JP |
2012-104594 |
Claims
1. An air conditioning system comprising: a plurality of indoor
units; an outdoor unit sharing a refrigerant system with the
plurality of indoor units; a first temperature sensor configured to
detect an outdoor air temperature; a second temperature sensor
configured to detect a temperature of a heat exchanger of the
outdoor unit; a human detection sensor configured to detect whether
or not there is a person in an air blowable region of each indoor
unit; and a control section configured to selectively execute a
first defrosting operation mode and a second defrosting operation
mode, the first defrosting operation mode being a mode in which a
defrosting operation is performed while fans of all the indoor
units are stopped, and the second defrosting operation mode being a
mode in which, when it is estimated that a frost formation amount
in the heat exchanger exceeds a threshold value on the basis of the
respective temperatures detected by the first and second
temperature sensors, the indoor unit for which the human detection
sensor detects no person in the air blowable region thereof is
preferentially selected, and a defrosting operation is performed
while the fan of the indoor unit is forcibly operated.
2. The air conditioning system according to claim 1, wherein the
control section determines whether or not the forcible operation
needs to be strengthened, on the basis of the temperature detected
by the second temperature sensor after a certain time has elapsed
since the execution of the second defrosting operation mode has
been started, and only when the forcible operation needs to be
strengthened, increases at least one of a revolution speed of the
fan and the number of indoor units whose fans are operated.
3. The air conditioning system according to claim 1, wherein the
outdoor unit is provided with a setting switch for allowing use of
the second defrosting operation mode.
4. The air conditioning system according to claim 1, wherein in the
case where at least two systems of a first system and a second
system each including the indoor units, the outdoor unit, and the
first and second temperature sensors are provided and the indoor
units of the two systems are provided in a mixed manner in one
room, when executing the second defrosting operation mode in the
first system, the control section operates the fans of the indoor
units in the room with the second system set at a heating
operation.
5. A defrosting operation method performed in an air conditioning
system including a plurality of indoor units and an outdoor unit
sharing a refrigerant system with the plurality of indoor units,
the defrosting operation method comprising: detecting an outdoor
air temperature and a temperature of a heat exchanger of the
outdoor unit by respective temperature sensors; detecting whether
or not there is a person in an air blowable region of each indoor
unit by a human detection sensor; and selectively executing, by a
control section, a first defrosting operation mode and a second
defrosting operation mode, the first defrosting operation mode
being a mode in which a defrosting operation is performed while
fans of all the indoor units are stopped, and the second defrosting
operation mode being a mode in which, when it is estimated that a
frost formation amount in the heat exchanger exceeds a threshold
value on the basis of the respective temperatures detected by the
first and second temperature sensors, the indoor unit for which the
human detection sensor detects no person in the air blowable region
thereof is preferentially selected, and a defrosting operation is
performed while the fan of the indoor unit is forcibly
operated.
6. The air conditioning system according to claim 2, wherein the
outdoor unit is provided with a setting switch for allowing use of
the second defrosting operation mode.
Description
TECHNICAL FIELD
[0001] The present invention relates to an air conditioning system
with use of an air conditioner, and particularly, relates to a
defrosting operation for removing frost formed in a heat exchanger
of an outdoor unit.
BACKGROUND ART
[0002] When an air conditioner performs a heating operation, in a
cold area, frost may be formed in a heat exchanger of an outdoor
unit, and the frost formation amount may be great. Since frost
formation hinders heat exchange, it is necessary to perform a
defrosting operation (for example, see Patent Literature 1).
CITATION LIST
Patent Literature
[0003] PATENT LITERATURE 1: Japanese Laid-Open Patent Publication
No. 2010-96474
SUMMARY OF INVENTION
Technical Problem
[0004] However, in the case where the outdoor air temperature is
very low, a conventional air conditioner as described above may
have difficulty removing frost by a defrosting operation. Since
heating cannot be performed during the defrosting operation, it is
desirable to complete the defrosting as quickly as possible.
[0005] Considering the above problems, an object of the present
invention is to provide an air conditioning system and a defrosting
operation method that can reduce time required for defrosting.
Solution to Problem
[0006] (1) An air conditioning system of the present invention
includes: a plurality of indoor units; an outdoor unit sharing a
refrigerant system with the plurality of indoor units; a first
temperature sensor configured to detect an outdoor air temperature;
a second temperature sensor configured to detect a temperature of a
heat exchanger of the outdoor unit; a human detection sensor
configured to detect whether or not there is a person in an air
blowable region of each indoor unit; and a control section
configured to selectively execute a first defrosting operation mode
and a second defrosting operation mode, the first defrosting
operation mode being a mode in which a defrosting operation is
performed while fans of all the indoor units are stopped, and the
second defrosting operation mode being a mode in which, when it is
estimated that a frost formation amount in the heat exchanger
exceeds a threshold value on the basis of the respective
temperatures detected by the first and second temperature sensors,
the indoor unit for which the human detection sensor detects no
person in the air blowable region thereof is preferentially
selected, and a defrosting operation is performed while the fan of
the indoor unit is forcibly operated.
[0007] In the air conditioning system configured as described
above, when it is estimated that the frost formation amount in the
heat exchanger exceeds the threshold value, the defrosting
operation is performed while the fan of at least one indoor unit is
forcibly operated. By operating the fan, heat exchange between the
indoor air and the refrigerant is promoted, so that the defrosting
is further swiftly performed. In addition, although cold air is
blown into the room by the operation of the fan, there is no fear
that discomfort (feeling cold) is given as long as there is no
person in the air blowable region.
[0008] (2) In addition, in the air conditioning system of the above
(1), the control section may determine whether or not the forcible
operation needs to be strengthened, on the basis of the temperature
detected by the second temperature sensor after a certain time has
elapsed since the execution of the second defrosting operation mode
has been started, and only when the forcible operation needs to be
strengthened, may increase at least one of a revolution speed of
the fan and the number of indoor units whose fans are operated.
[0009] For example, in the case where the temperature of the heat
exchanger does not become higher than a predetermined value even
after the certain time has elapsed since the execution of the
second defrosting operation mode has been started, that is, in the
case where progress of the defrosting is slow because the frost
formation amount is great, at least one of the revolution speed of
the fan and the number of indoor units whose fans are operated is
increased, whereby heat exchange between the indoor air and the
refrigerant is further promoted. Thus, defrosting in the case of
great frost formation amount can be swiftly performed.
[0010] (3) In addition, in the air conditioning system of the above
(1) or (2), the outdoor unit may be provided with a setting switch
for allowing use of the second defrosting operation mode.
[0011] In this case, use of the second defrosting operation mode
can be easily allowed by an operation on the setting switch. In
addition, if a user does not desire the second defrosting operation
mode, the setting can be easily cancelled.
[0012] (4) In addition, in the air conditioning system of the above
(1), in the case where at least two systems of a first system and a
second system each including the indoor units, the outdoor unit,
and the first and second temperature sensors are provided and the
indoor units of the two systems are provided in a mixed manner in
one room, when executing the second defrosting operation mode in
the first system, the control section may operate the fans of the
indoor units in the room with the second system set at a heating
operation.
[0013] In this case, when there is a person in the room, since warm
air can be blown from the indoor units of the second system though
cold air is blown from the indoor units of the first system, it is
possible to neutralize (or alleviate) discomfort due to blow of
cold air, in the room as a whole.
[0014] (5) Another aspect of the present invention is a defrosting
operation method performed in an air conditioning system including
a plurality of indoor units and an outdoor unit sharing a
refrigerant system with the plurality of indoor units, the
defrosting operation method including: (a) detecting an outdoor air
temperature and a temperature of a heat exchanger of the outdoor
unit by respective temperature sensors; (b) detecting whether or
not there is a person in an air blowable region of each indoor unit
by a human detection sensor; and (c) selectively executing, by a
control section, a first defrosting operation mode and a second
defrosting operation mode, the first defrosting operation mode
being a mode in which a defrosting pperation is performed while
fans of all the indoor units are stopped, and the second defrosting
operation mode being a mode in which, when it is estimated that a
frost formation amount in the heat exchanger exceeds a threshold
value on the basis of the respective temperatures detected by the
first and second temperature sensors, the indoor unit for which the
human detection sensor detects no person in the air blowable region
thereof is preferentially selected, and a defrosting operation is
performed while the fan of the indoor unit is forcibly
operated.
[0015] In the defrosting operation method as described above, when
it is estimated that the frost formation amount in the heat
exchanger exceeds the threshold value, the defrosting operation is
performed while the fan of at least one indoor unit is forcibly
operated. By operating the fan, heat exchange between the indoor
air and the refrigerant is promoted, so that the defrosting is
further swiftly performed. In addition, although cold air is blown
into the room by the operation of the fan, there is no fear that
discomfort (feeling cold) is given as long as there is no person in
the air blowable region.
Advantageous Effects of Invention
[0016] The air conditioning system or the defrosting operation
method of the present invention can reduce time required for
defrosting.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a configuration diagram of an air conditioning
system according to the first embodiment of the present
invention.
[0018] FIG. 2 is a diagram showing the schematic configuration of
an outdoor unit.
[0019] FIG. 3 is a flowchart showing a procedure of a defrosting
operation method of the present embodiment performed by a control
section of the outdoor unit.
[0020] FIG. 4 is a diagram showing the case where a fan of one
indoor unit is operated when a person is present in a region for a
certain indoor unit, in the same configuration diagram as in FIG.
1.
[0021] FIG. 5 is a diagram showing the case where fans of two
indoor units are operated when a person is present in a region for
a certain indoor unit, in the same configuration diagram as in FIG.
1.
[0022] FIG. 6 is a configuration diagram of an air conditioning
system according to the second embodiment of the present
invention.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0023] FIG. 1 is a configuration diagram of an air conditioning
system according to the first embodiment of the present invention.
In FIG. 1, in the air conditioning system 100, one outdoor unit 1
and a plurality of (three) indoor units 2, 3, and 4 are connected
via a refrigerant pipe 5, thereby sharing a refrigerant system. In
addition, the outdoor unit 1 and the indoor units 2, 3, and 4 are
connected to each other via a communication line 6. Remote
controllers 2r, 3r, and 4r for operation are respectively connected
to the indoor units 2, 3, and 4. The indoor units 2, 3, and 4
respectively have fans 2f, 3f and 4f therein.
[0024] The number of the indoor units is merely an example. In
addition, although one outdoor unit 1 is provided, a plurality of
outdoor units may be provided as necessary. In addition, a power
line is not shown in the drawings.
[0025] The indoor units 2, 3, and 4 are provided with human
detection sensors 2s, 3s, and 4s, respectively. The human detection
sensors 2s, 3s, and 4s are, for example, pyroelectric Infrared
sensors, and can detect infrared light emitted by a person present
in an air blowable region A2, A3, or A4 of the indoor unit 2, 3, or
4, thereby recognizing presence or absence of a person. In the
drawings, a simple circular (conical) region is shown for
simplification.
[0026] In practice, in accordance with expansion of the air
blowable region of each indoor unit, a plurality of human detection
sensors may be provided per indoor unit such that detection target
regions of these sensors are shifted from each other, so as to
allow these sensors as a whole to detect a wide range.
[0027] The human detection sensors 2s, 3s, and 4s may not be
necessarily provided on housings of the indoor units 2, 3, and 4 as
accessories thereof. For example, the human detection sensors 2s,
3s, and 4s may be provided on a ceiling of a room, and their
outputs may be transmitted to the indoor units 2, 3, and 4 or the
outdoor unit 1. In addition, in the case where the indoor units 2,
3, and 4 are provided in separate rooms, whether or not there is a
person in each room instead of the air blowable region may be
detected.
[0028] FIG. 2 is a diagram showing the schematic configuration of
the outdoor unit 1. The outdoor unit 1 has, in a housing 11, a
compressor 12, a four way valve 13, an accumulator 14, a heat
exchanger 15, an expansion valve 16, a fan 17, temperature sensors
18 and 19, and a control section 20. The temperature sensor 19 is,
for example, a thermistor, and is attached in contact with a
refrigerant tube P1 at an end of the heat exchanger 15. The
temperature sensor 19 detects a temperature Tb at the end of the
heat exchanger 15 which is the low-temperature side (hereinafter,
simply referred to as a temperature of the heat exchanger 15). When
the outdoor unit 1 is performing operation without frost formation
in the heat exchanger 15, the temperature detected by the
temperature sensor 19 is almost constant. On the other hand, the
temperature sensor 18 is, for example, a thermistor, and detects
the temperature of outdoor air taken in by operation of the fan
17.
[0029] The temperature sensors 18 and 19 are connected to the
control section 20 via cables 18a and 19a, respectively. The
control section 20 has a CPU and other central control functions,
thereby controlling each actuator (the compressor 12, the four way
valve 13, the expansion valve 16, the fan 17, etc.) in the outdoor
unit 1 and the indoor units 2 to 4.
[0030] In addition, the control section 20 is provided with a
setting switch 20s. By operating the setting switch 20s, either the
case of using only a first defrosting operation mode or the case of
selectively using first and second defrosting operation modes as
described later can be selected as appropriate in accordance with a
user's desire, for example.
[0031] In FIG. 2, in a cooling operation, the four way valve 13
becomes a state indicated by a solid line in the drawing, and a
high-pressure gas refrigerant ejected from the compressor 12 is
subjected to heat exchange with outdoor air by the heat exchanger
15, and is thereby condensed to be a liquid refrigerant. The liquid
refrigerant is decompressed by the expansion valve 16, and then
sent to the indoor units 2 to 4 (FIG. 1). After evaporation by heat
exchange with indoor air in the indoor units 2 to 4, the gas
refrigerant returns to the outdoor unit 1, passes through the four
way valve 13 and the accumulator 14, and then is sent to the
compressor 12. The cooling operation is performed through
repetition of such a cycle.
[0032] In a heating operation, the four way valve 13 becomes a
state indicated by a dotted line in the drawing, and a
high-pressure gas refrigerant ejected from the compressor 12 is
sent to the indoor units 2, 3, and 4 (FIG. 1), in which the gas
refrigerant is subjected to heat exchange with indoor air and is
thereby condensed to be a liquid refrigerant. The liquid
refrigerant returns to the outdoor unit 1 and is decompressed by
the expansion valve 16. Thereafter, the liquid refrigerant is
subjected to heat exchange with outdoor air by the heat exchanger
15, and is thereby evaporated. After the evaporation, the gas
refrigerant passes through the four way valve 13 and the
accumulator 14 and then is sent to the compressor 12. The heating
operation is performed through repetition of such a cycle.
[0033] When a heating operation is performed at a low outdoor
temperature, frost may be formed in the heat exchanger 15 of the
outdoor unit 1. If the formed frost is left to grow, the heating
efficiency is deteriorated. Therefore, the heating operation is
temporarily stopped and a defrosting operation is performed. Flow
of a refrigerant in the defrosting operation is the same as in the
cooling operation. At this time, conventionally, the fans of the
indoor units 2 to 4 are stopped so that cold air does not flow out
into the room.
[0034] The above defrosting operation can be performed based on the
temperature Tb of the heat exchanger 15 in the outdoor unit 1, for
example. In a normal heating operation, the temperature Tb of the
heat exchanger 15 is kept substantially at a constant value To as
long as there is no frost formation. However, as the frost formed
in the heat exchanger 15 gradually increases while the heating
operation is continued, the temperature Tb of the heat exchanger 15
gradually decreases. Then, when the temperature Tb detected by the
temperature sensor 19 further decreases by more than a temperature
decrease width .DELTA.T from the above To, that is, in the case of
Tb<(To-.DELTA.T), it is determined that the frost formation
amount in the heat exchanger 15 has become equal to or greater than
a reference frost formation amount. The reference frost formation
amount is a frost formation amount "just before" the efficiency of
the heat exchanger 15 reduces and a problem occurs on the hearing
operation unless defrosting is performed.
[0035] It is noted that the defrosting operation may be set so as
to be finished when the temperature Tb of the heat exchanger 15 has
increased to To, for example.
[0036] In addition, as a trigger for start and finish other than
the above start and finish of the defrosting operation, for
example, under a predetermined outdoor air temperature condition,
when a heating operation has been continuously performed for a
certain time, it may be estimated that frost formation has
occurred, and a defrosting operation may be automatically
performed. In addition, when the defrosting operation has performed
for a certain time, it may be estimated that defrosting has been
completed, and the defrosting operation may be automatically
finished.
[0037] The air conditioning system 100 of the present embodiment
executes an advanced defrosting operation, besides the normal
defrosting operation as described above. Hereinafter, the advanced
defrosting operation method will be described in detail.
[0038] FIG. 3 is a flowchart showing a procedure of the defrosting
operation method of the present embodiment performed by the control
section 20 of the outdoor unit 1. It is noted that instructions to
start and finish the defrosting operation are performed in the
above manner, and therefore they are shown in a simplified manner
in the flowchart. That is, the flowchart mainly shows selective use
of two modes in the defrosting operation.
[0039] When a defrosting operation is started, the control section
20 stops all the fans of the indoor units 2 to 4 (step S1). This is
a normal defrosting operation and is referred to as a first
defrosting operation mode.
[0040] Next, the control section 20 determines whether or not the
temperature Tb of the heat exchanger 15 is lower than 10.degree. C.
(step S2). Here, if the temperature Tb is equal to or higher than
10.degree. C., it can be estimated that the frost formation amount
is comparatively small. Therefore, the control section 20 continues
the first defrosting operation mode until the defrosting operation
is finished (steps S1, S2, and S8 are repeated). If an instruction
to finish the defrosting operation is issued in step S8, the
defrosting operation is finished.
[0041] On the other hand, if the temperature Tb of the heat
exchanger 15 is lower than 10.degree. C., the control section 20
determines whether or not a temperature Ta of the outdoor air
detected by the temperature sensor 19 is lower than 0.degree. C.
(step S3). Here, if the temperature Ta is equal to or higher than
0.degree. C., it can be estimated that the frost formation amount
is comparatively small. Therefore, the control section 20 continues
the first defrosting operation mode until the defrosting operation
is finished (steps S1, S2, S3, and S8 are repeated). If an
instruction to finish the defrosting operation is issued in step
S8, the defrosting operation is finished.
[0042] On the other hand, in step S3, if the temperature Ta of the
outdoor air is lower than 0.degree. C., that is, two conditions of
Tb<10.degree. C. and Ta<0.degree. C. are satisfied in a logic
of AND, the control section 20 estimates that the frost formation
amount exceeds a threshold value, and executes a second defrosting
operation mode (step S4). It is noted that the threshold value of
the frost formation amount is greater than the above-described
reference frost formation amount.
[0043] In the second defrosting operation mode, the fans of one or
more of the indoor units 2 to 4 are forcibly operated. By operating
the fans, heat exchange between the indoor air and the refrigerant
is promoted, so that the defrosting is further swiftly performed.
The more the number of the indoor units whose fans are operated,
the more swiftly the defrosting can be performed. In addition,
under the same number of the indoor units whose fans are operated,
the more the air blow amount is, the more swiftly the defrosting
can be performed.
[0044] However, since the defrosting operation uses the same
refrigerant cycle as the cooling operation, a cold air is blown
into the room when the fans are operated. In this case, a person at
a position to which the cold air is blown will feel cold and
uncomfortable.
[0045] FIG. 4 is the same diagram as in FIG. 1, showing the case
where there is a person in a region A4 of the indoor unit 4. In
this case, the presence of the person is detected by the human
detection sensor 4s. The detected signal is transmitted to the
control section 20 of the outdoor unit 1. On the other hand, if
there is no person in regions A2 and A3 of the indoor units 2 and
3, no detected signal is transmitted from the human detection
sensors 2s and 3s. Accordingly, the control section 20
preferentially selects and operates the fans 2f and 3f of the
indoor units 2 and 3 which detect no person in then air blowable
regions.
[0046] FIG. 4 shows the case where the fan 2f of the indoor unit 2
is operated, as an example. Although cold air is blown to the
region A2 by the operation of the fan 2f, there is no person in
that region and therefore no person feels uncomfortable.
[0047] FIG. 5 shows the case where the fans 2f and 3f of the indoor
units 2 and 3 are operated. Although cold air is blown to the
regions A2 and A3 by the operation of the fans 2f and 3f, there is
no person in those regions and therefore no person feels
uncomfortable.
[0048] Returning to FIG. 3, while executing the second defrosting
operation mode, the control section 20 waits for the temperature of
the heat exchanger 15 to become higher than 11.degree. C. during a
certain time after the forcible operation of the fans has been
started (return from steps S5 and S6 to step S4 is repeated). The
temperature 11.degree. C. is a temperature at which it is
determined that the frost formation amount has become smaller than
the threshold value as a result of the defrosting operation in the
second defrosting operation mode and therefore the first defrosting
operation mode is sufficient. The reason why a difference by
1.degree. C. from 10.degree. C. in step S2 is provided is to avoid
hunting of the operation mode behavior and to ensure that the frost
formation amount is decreased enough to return to the first
defrosting operation mode.
[0049] If the temperature of the heat exchanger 15 has become
higher than 11.degree. C. before the certain time elapse, the
process returns through step S8 to step S1, and thereafter, the
control section 20 continues the first defrosting operation mode
until the defrosting operation is finished (steps S1, S2, and S8
are repeated). If an instruction to finish the defrosting operation
is issued in step S8, the defrosting operation is finished.
[0050] On the other hand, in step S6, if the certain time has
elapsed after the forcible operation has been started without the
temperature of the heat exchanger 15 becoming higher than
11.degree. C., the control section 20 strengthens the forcible
operation (step S7). This is performed by increasing the
above-described number of the indoor units whose fans are operated
and/or increasing the air blow amount, i.e., the revolution speed
of each fan. Thus, the defrosting can be swiftly performed.
[0051] It is noted that in the above air conditioning
system/defrosting operation method, the fan of the indoor unit for
which there is a person in the air blowable region thereof is not a
target of preferential operation, so that it is desirable to avoid
the operation thereof. However, this does not mean that the
operation must not be performed. If a user allows cold air to be
blown for swift defrosting, the fans of all the indoor units may be
operated irrespective of presence or absence of a person, whereby
the defrosting can be further swiftly performed.
[0052] Since the setting switch 20s (FIG. 2) for allowing use of
the second defrosting operation mode is provided on the outdoor
unit 1, use of the second defrosting operation mode can be easily
allowed by an operation on the setting switch 20s at the time of
installation or maintenance. In addition, if a user does not desire
the second defrosting operation mode, the setting can be easily
cancelled.
[0053] It is noted that the specific values used for the conditions
for executing the second defrosting operation mode (steps S2 and S3
in FIG. 3) and the condition for finishing the second defrosting
operation mode (step S5) in the above embodiment are merely
examples, and may be slightly changed as appropriate depending on
the use environment.
Second Embodiment
[0054] FIG. 6 is a configuration diagram of an air conditioning
system according to the second embodiment of the present invention.
In FIG. 6, the air conditioning system 200 has two separate
refrigerant systems. In the case where the two systems are an X
system and a Y system, the X system includes one outdoor unit 1x
and a plurality of (three) indoor units 2x, 3x, and 4x, which are
connected via a refrigerant pipe 5x, thereby sharing a refrigerant
system. In addition, the outdoor unit 1x and the indoor units 2x,
3x, and 4x are connected to each other via a communication line
6x.
[0055] In addition, the Y system includes one outdoor unit 1y and a
plurality of (three) indoor units 2y, 3y, and 4y, which are
connected via a refrigerant pipe 5y, thereby sharing a refrigerant
system. In addition, the outdoor unit 1y and the indoor units 2y,
3y, and 4y are connected to each other via a communication line
6y.
[0056] It is noted that the number of the indoor units in each
system is merely an example. In addition, although one outdoor unit
1x and one outdoor unit 1y are provided, a plurality of outdoor
units 1x or a plurality of outdoor units 1y may be provided as
necessary.
[0057] A space as an air conditioning target is, for example, one
broad room 30 such as one floor of a building, and has no partition
wall. In addition, for example, the outdoor unit 1x at the left is
provided under a roof R and does not receive much sunshine.
Therefore, for example, at a low temperature that is lower than
0.degree. C., frost formation easily occurs even in a good weather,
and the frost formation amount is likely to be great. On the other
hand, the outdoor unit 1y at the right is provided at a place that
receives sunshine in the daytime, so that frost formation hardly
occurs or even if frost formation occurs, the amount thereof is
comparatively small.
[0058] The other detailed configuration is the same as in the first
embodiment.
[0059] In the air conditioning system 200 of the second embodiment
as described above, a state can frequently occur in which frost is
formed in the outdoor unit 1x and a defrosting operation is needed
but the outdoor unit 1y does not need a defrosting operation. In
such a case, for example, the X system can perform a defrosting
operation and the Y system can perform a heating operation.
[0060] The defrosting operation method can be performed in the
manner shown in the flowchart in FIG. 3, as in the first
embodiment. Although cold air is preferentially blown to a space in
which there is no person as in the above case, the cold air can
flow convectively because the room is one floor. However, since
warm air can be blown from the indoor units (2y, 3y, and 4y) of the
Y system though cold air is blown from the indoor units (for
example, 2x and 4x) of the X system, it is possible to neutralize
(or alleviate) discomfort due to blow of cold air, in the room as a
whole. The fan of the indoor unit 3x is not operated because there
is a person in the air blowable region thereof.
[0061] Although the configuration in FIG. 6 has two systems, three
or more systems may be provided in a mixed manner. In this case,
only one system may execute the second defrosting operation mode as
necessary while the other two or more systems perform heating
operations, whereby discomfort due to blow of cold air can be
further alleviated in the room as a whole.
REFERENCE SIGNS LIST
[0062] 1 outdoor unit
[0063] 2 (2x, 2y), 3 (3x, 3y), 4 (4x, 4y) indoor unit
[0064] 2f, 3f, 4f fan
[0065] 2s, 3s, 4s human detection sensor
[0066] 15 heat exchanger
[0067] 18, 19 temperature sensor
[0068] 20 control section
[0069] 20s setting switch
[0070] 100, 200 air conditioning system
* * * * *