Air conditioning apparatus connecting one outdoor unit with several indoor units through several refrigerant tubes and signal conductors

An air conditioning apparatus in which one outdoor unit is connected to several indoor units through respective refrigerant tubes and signal conductors. The outdoor unit has compressors for discharging refrigerant and an outdoor heat exchanger. Each outdoor unit has an indoor heat exchanger and an indoor heat exchanger temperature sensor. When an operating device signals a check node, the compressors are stopped for a predetermined time period. Then the compressors are operated to sequentially discharge refrigerant to each indoor unit. A checking device then monitors the signal conductors of each indoor unit for a signal indicating a certain temperature condition. Based on the signals received, the checking device determines whether the indoor units are properly connected to the outdoor unit.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a multiple-type air conditioning apparatus 
comprising one outdoor unit and several indoor units. 
2. Description of the Related Art 
Said multiple-type air conditioning apparatus connects one outdoor unit 
with several indoor units through several refrigerant tubes and signal 
conductors. 
Said signal conductors are used to send commands and signals related to 
operation. 
To install said air conditioning apparatus in a building, refrigerant tubes 
must properly be connected between the outdoor unit and several indoor 
units, and signal conductors must also be properly connected between the 
outdoor unit and several indoor units. 
However, refrigerant tubes may be abnormally connected due to erroneous 
work, or signal conductors may be abnormally connected due to erroneous 
wiring. 
If any of the above error occurs, the air conditioning apparatus will not 
function properly. Therefore, it is necessary to carefully check out the 
connection state of the refrigerant tubes and signal conductors by 
executing test operations after installing the air conditioning apparatus. 
However, the above checkout is very troublesome and errors may be 
overlooked by human operators. 
Therefore, an air conditioning apparatus is developed which automatically 
checks the connection state between one outdoor unit and several indoor 
units. 
For example, an air conditioning apparatus disclosed in the official 
gazette of Japanese Patent TOKKOSHO 61-54147, checks the connection state 
between one outdoor unit 2 and several indoor units 1, 1' by sequentially 
flowing refrigerant through several indoor units 1, 1' to monitor the 
temperature change in several indoor units 1, 1'. 
In this publication, however, only the method of checking the connection 
state is disclosed, no concrete control method is disclosed showing the 
relation between the checking of the connection state and the normal air 
conditioning operation. Therefore, there may occur an erroneous detection 
of the connection state. 
The air conditioning apparatus disclosed in the official gazette of 
Japanese Patent JIKKAISHO 63-113843 is equipped with several outdoor units 
X and Y, in which the outdoor unit X connects with the indoor units A 
through F and the outdoor unit Y connects with the indoor units G through 
L. 
The air conditioning apparatus checks which outdoor unit an indoor unit 
outputting the operation command is connected to, X or Y, by monitoring 
the suction-side pressure of the compressor 1 of the outdoor unit X and 
that of the compressor 1 of the outdoor unit Y. 
However, this air conditioning apparatus cannot check which outdoor unit an 
indoor unit is connected to, X or Y. Therefore, it is impossible to check 
the connection state between the outdoor unit X and the indoor units A 
through F and between the outdoor unit Y and the indoor units G through L. 
SUMMARY OF THE INVENTION 
It is the object of the present invention to greatly decrease an operator's 
load and realize proper operation after installation by automatically, 
quickly, and accurately checking the connection state between one outdoor 
unit and several indoor units. 
The present invention comprises: 
compressors installed on an outdoor unit, which take in, compress, and 
discharge refrigerant, 
an outdoor heat exchanger installed on said outdoor unit, which exchanges 
the heat of incoming refrigerant for that of outdoor air, 
several indoor heat exchangers installed on several indoor units 
respectively, which exchange the heat of incoming refrigerant for that of 
indoor air, 
a refrigeration cycle connecting said compressors of, said outdoor and said 
indoor heat exchangers by refrigerant tubes, several temperature sensors 
installed on said indoor units respectively, which detect the temperature 
of said indoor heat exchangers, 
an operating means to be operated to check connection errors between said 
outdoor unit and said indoor units, 
a means to sequentially flow refrigerant through said indoor units by 
temporarily stopping said compressor before restarting it when said 
operating means is operated, 
means installed on each said indoor units, which outputs the signal to 
indicate that the temperature change detected by an associated temperature 
sensor exceeds a certain value and sends the signal to an associated 
signal conductor when said operating means is operated, and 
a means to check if said outdoor unit is normally connected to said indoor 
units by monitoring tee signal of said signal conductors when said 
operating means is operated. 
Other objects, features, and characteristics of the present invention, as 
well as methods, operation, and functions of the related elements of the 
structure, and the combination of parts and economies of manufacture, will 
become apparent from the following detailed description of the preferred 
embodiments and accompanying drawings, all of which form a part of this 
specification, wherein like reference numerals designate corresponding 
parts in the various figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The following is the description of the first embodiment according to 
drawings. 
In FIG. 1, A is an outdoor unit. The branch unit B is connected to the 
outdoor unit A through refrigerant tubes. The branch unit B connects with 
the indoor units C.sub.1, C.sub.2, and C.sub.3 through refrigerant tubes. 
In the outdoor unit A, branch unit B, and indoor units C.sub.1, C.sub.2 and 
C.sub.3, the following heat-pump-type refrigeration cycle is configured. 
The outdoor unit A has the variable-capacity-type compressors 1 and 2. The 
compressors 1 and 2 take in refrigerant from an intake, compress it, and 
discharge it from an outlet. 
The outdoor heat exchanger 6 is connected to the outlet of the compressors 
1 and 2 through the forward check valves 3 and 4 and the four-way valve 5, 
which exchanges the heat of incoming refrigerant for that of outdoor air. 
The liquid tank 8 is connected to the outdoor heat exchanger 6 through the 
forward check valve 7. The header 9 is connected to the liquid tank 8. 
The expansion valve 10 is connected between the liquid tank 8 and the 
outdoor heat exchanger 6. 
The liquid-side tube W is connected to said header 9. The liquid-side tube 
W is branched to three liquid-side tubes--W.sub.1, W.sub.2, and W.sub.3. 
The liquid-side tubes W.sub.1, W.sub.2, and W.sub.3 connect with the indoor 
heat exchangers 24, 34, and 44 of the indoor units C.sub.1, C.sub.2, and 
C.sub.3 through the pulse motor valves (hereafter called PMV) 21, 31, and 
41 and the expansion valves 22, 32, and 42. The indoor heat exchangers 24, 
34, and 44 exchange the heat of incoming refrigerant for that of indoor 
air. 
The forward check valves 23, 33, and 43 are connected between the indoor 
heat exchangers 24, 34, and 44 and the PMVs 21, 31, and 41. 
The gas-side tubes G.sub.1, G.sub.2, and G.sub.3 are connected to the 
indoor heat exchangers 24, 34, and 44. 
The gas-side tubes G.sub.1 through G.sub.3 are connected to the gas-side 
tube G. 
The gas-side tube G is connected to the header 11. The header 11 is 
connected to the inlet of the compressors 1 and 2 through said four-way 
valve 5 and the accumulator 12. 
That is, unless the four-way valve 5 operates, refrigerant flows in the 
direction of the arrow shown by a continuous line in the drawing and 
cooling operation is set. When the four-way valve 5 is operated and 
switched, refrigerant flows in the direction of the arrow shown by a 
broken line in the drawing and heating operation is set. 
The oil separator 13 is installed on the tube between the outlet of the 
compressor 1 and the check valve 3. The oil bypass 14 is connected between 
the oil separator 13 and the inlet of the compressor 1. 
The oil separator 15 is installed on the tube between the outlet of the 
compressor 2 and the check valve 4. The oil bypass 16 is connected between 
the oil separator 15 and the inlet of the compressor 2. 
The tube 17 is connected between the reference oil level positions of the 
cases of the compressors 1 and 2. The tube 17 flows the lubricating oil of 
the compressors 1 and 2 alternately. 
The outdoor fan 18 is installed on the outdoor unit A to circulate outdoor 
air through the outdoor heat exchanger 6. 
The heat sensitive element 10a is installed on the tube between the 
four-way valve 5 and the outdoor heat exchanger 6. The heat sensitive 
element 10a is an accessory of the expansion valve 10. The expansion valve 
10 detects the difference between the temperature detected by the heat 
sensitive element 10a and that of the refrigerant flowing through the 
expansion valve 10, that is, the degree of superheat of the refrigerant 
flowing through the outdoor heat exchanger 6. Moreover, the expansion 
valve 10 controls the quantity of the refrigerant flowing through the 
outdoor heat exchanger 6 so that the detected degree of superheat will be 
constant. 
In the branch unit B, the heat sensitive elements 22a, 32a, and 42a are 
installed on the gas-side tubes G.sub.1 through G.sub.3. 
The heat sensitive elements 22a, 32a, and 42a are accessories of the 
expansion valves 22, 32, and 42. 
The expansion valves 22, 32, and 42 detect the difference between the 
temperature detected by the heat sensitive elements 22a, 32a, and 42a and 
that of the refrigerant flowing through the expansion valves 22, 32, and 
42. Moreover, the expansion valves 22, 32, and 42 control the quantity of 
the refrigerant flowing through the outdoor heat exchangers 24, 34, and 44 
so that the detected degree of superheat will be constant. 
In the indoor units C.sub.1 through C.sub.3, the temperature sensors 25, 
35, and 45 are installed on the indoor heat exchangers 24, 34, and 44. The 
heat sensors 25, 35, and 45 respectively detect the temperature of each 
indoor heat exchanger. 
The indoor fans 26, 36, and 46 are installed on the indoor units C.sub.1 
through C.sub.3 to circulate indoor air through the indoor heat exchangers 
24, 34, and 44. 
FIG. 2 shows a control circuit. 
The outdoor unit A has the outdoor controller 50. The outdoor controller 50 
comprises a microcomputer and its peripheral circuits. 
The branch controller 60 of the branch unit B is connected to the outdoor 
controller 50 through the signal conductor S.sub.0. The branch controller 
60 comprises a microcomputer and its peripheral circuits. 
The indoor controller 70, 80, and 90 of the indoor units C.sub.1 through 
C.sub.3 are connected to the branch controller 60 through the signal 
conductors S.sub.1, S.sub.2, and S.sub.3 respectively. The indoor 
controller 70, 80, and 90 comprise a microcomputer and its peripheral 
circuits respectively. 
The outdoor controller 50 connects with the four-way valve 5, the inverter 
circuits 51 and 52, the checking switching 53 which is an operating means, 
the indicator 54, the temperature sensor 55, and the outdoor fan motor 
18M. 
The inverter circuit 51 and 52 rectifies the voltage of the AC power supply 
56 and converts the voltage into the voltage with the prescribed frequency 
corresponding to the command from the outdoor controller 50 before 
outputting it. The output voltages of the inverter circuits 51 and 52 are 
supplied to the compressor motors 1M and 2M respectively as the driving 
power. 
The checking switch 53 is operated to check if the indoor units C.sub.1 
through C.sub.3 are normally connected to the outdoor unit A. 
The temperature sensor 55 detects the temperature of outdoor air. 
The branch controller 60 connects with the PMVs 11, 21, and 31, and the 
timers 61 through 63. 
The indoor controllers 70, 80, and 90 connect with the operation units 71, 
81, and 91, the temperature sensors, 72, 82, 92, said temperature sensors 
15, 25, and 35, and the indoor fan motors 26M, 36M, and 46M. 
The temperature sensors 72, 82, and 92 detect the temperature of indoor 
air. 
The following is the description of operations. 
First, the control by the indoor controllers 70, 80, and 90 is described 
according to FIG. 3. 
When the operation switch of the operation unit 71 is turned on (step D1), 
the operation mode set in the operation unit 71 (cooling- or 
heating-operation mode) is requested to the branch unit B (step D2). Then, 
the difference between the temperature set in the operation unit 71 and 
indoor air temperature detected by the temperature sensor 72 is obtained 
(step D3) and the power level corresponding to the difference (cooling 
power level or heating power level) is requested to the branch unit B 
(step D4). 
When the operation start command is given to the indoor controller 70 from 
the branch unit B (step D5), the indoor fan 26 is operated according to 
necessity (step D6). 
When the operation stop command is given to the indoor controller 70 from 
the branch unit B (step D7), the indoor fan 26 is stopped (step D8). 
When the checking signal is given to the indoor controller 70 from the 
branch unit B (step D9), the check mode routine is executed (step D10). 
FIG. 4 shows the check mode routine. 
In the check mode routine, the indoor fan 26 is operated according to 
necessity (step D11) and the change of the temperature (temperature of the 
indoor heat exchanger 24) detected by the temperature sensor 25 is 
monitored (step D12). When the temperature decreases to a certain value or 
lower (step D13), the release signal indicating the temperature change is 
sent to the branch unit B through the signal conductor S.sub.1 (step D14). 
When the operation switch of the operation unit 81 is turned on (step D1), 
the operation mode (cooling- or heating-operation mode) set in the 
operation unit 81 is requested to the branch unit B (step D2). Then, the 
difference between the temperature set in the operation unit 81 and the 
indoor air temperature detected by the temperature sensor 82 is obtained 
(step D3) and the power level corresponding to the difference (cooling 
power level or heating power level) is requested to the branch unit B 
(step D4). 
When the operation start command is given to the indoor controller 80 from 
the branch unit B (step D5), the indoor fan 36 is operated according to 
necessity (step D6). 
When the operation stop command is given to the indoor controller 80 from 
the branch unit B (step D7), the indoor fan 36 is stopped (step D8). 
When the checking signal is given to the indoor controller 80 from the 
branch unit B (step D9), the check mode routine is executed (step D10). 
FIG. 4 shows the check mode routine. 
In the check mode routine, the indoor fan 36 is operated according to 
necessity (step D11 and the change of the temperature (temperature of the 
indoor heat exchanger 34) detected by the temperature sensor 35 is 
monitored (step D12). When the temperature decreases to a certain value or 
lower (step D13), the release signal indicating the temperature decrease 
is sent to the branch unit B through the signal conductor S.sub.2 (step 
D14). 
When the operation switch of the operation unit 91 is turned on (step D1), 
the operation mode (cooling- or heating-operation mode) set in the 
operation unit 91 is requested to the branch unit B (step D2). Then, the 
difference between the temperature set in the operation unit 81 and the 
indoor air temperature detected by the temperature sensor 92 is obtained 
(step D3) and the power level corresponding to the difference (cooling 
power level or heating power level) is requested to the branch unit B 
(step D4). 
When the operation start command is given to the indoor controller 90 from 
the branch unit B (step D5), the indoor fan 46 is operated according to 
necessity (step D6). 
When the operation stop command is given to the indoor controller 90 from 
the branch unit B (step D7), the indoor fan 46 is stopped (step D8). 
When the checking signal is given to the indoor controller 90 from the 
branch unit B (step D9), the check mode routine is executed (step D10). 
FIG. 4 shows the check mode routine. 
In the check mode routine, the indoor fan 46 is operated according to 
necessity (step D11) and the change of the temperature (temperature of the 
indoor heat exchanger 44) detected by the temperature sensor 45 is 
monitored (step D12). When the temperature decreases to a certain value or 
lower (step D13), the release signal indicating the temperature decrease 
is sent to the branch unit B through the signal conductor S.sub.3 (step 
D14). 
Secondly, the control by the outdoor controller 50 is described below 
according to FIG. 5. 
Unless the checking switch 53 is turned on (step E1), the four-way valve 5 
is controlled according to the operation mode requested from the branch 
unit B (step E2). For example, the four-way valve 5 is not operated when 
the cooling operation mode is requested but it is operated when the 
heating operation mode is requested. 
At the same time, the compressors 1 and/or 2 are operated (step E3). 
The compressor 1 and/or compressor 2 being operated and the operation of 
one or both compressors frequency (output frequency of the inverter 
circuits 51 and 52) are controlled according to the power level requested 
from the branch unit B (step E4). 
Also, the outdoor fan 16 is operated according to necessity. When the 
checking switch 53 is turned on (step E1), the check mode routine is 
executed (step E6). FIG. 6 shows the check mode routine. 
In the check mode routine, the compressors 1 and 2 are stopped (step E11), 
the outdoor fan 16 is stopped (step E12), and the checking signal is sent 
to the branch unit B (step E13). 
When the cooling-operation start command is given from the branch unit B 
(step E14), the compressors 1 and/or 2 are operated. Also, the compressor 
1 and/or compressor 2 being operated and the operation frequency of one or 
both compressors are controlled according to the power level requested 
from the branch unit B (step E15). At the same time, the outdoor fan 16 is 
operated according to necessity (step E16). 
When the operation is started, the command indicating "under operation" is 
given to the branch unit B (step E17). 
When the command indicating an error is given from the branch unit B (step 
E18), the error contents to be commanded from the branch unit B is 
displayed on the indicator 54 (step E19). 
When the end signal is given from the branch unit B (step E20), the 
compressors 1 and 2 are stopped (step E21) and the outdoor fan 16 is 
stopped (step E22). 
The following is the description of the whole operation and the control by 
the branch controller 60 according to FIGS. 7A and 7B. 
In the branch controller 60, the following control is executed when the 
checking signal is not received from the outdoor unit A (step F1). 
Either the cooling- or heating-operation mode is determined according to 
the request for the operation mode from the indoor units C.sub.1 through 
C.sub.3 (step F2). 
For example, if the number of requests for the cooling operation mode is 
more than that of requests for the heating operation mode, the cooling 
operation mode is determined. If the number of requests for the heating 
operation mode is more than that of requests for the cooling operation 
mode, the heating operation mode is determined. If the number of requests 
for the cooling operation mode is equal to that of requests for the 
heating operation mode, the cooling operation mode is preferentially 
determined. 
The determined operation mode is requested to the outdoor unit A (step F3). 
It is checked if an operation mode is requested from the indoor unit 
C.sub.1 (step F4). 
If so, it is checked if the operation mode is the same as the 
above-determined operation mode (step F5). If so, the operation start 
command is sent to the indoor unit C.sub.1 (step F6) and the opening of 
the PMV 21 is controlled according to the power level requested from the 
indoor unit C.sub.1 (step F7). 
If an operation mode is not requested from the indoor unit C.sub.1 in the 
step F4 or the operation mode is not the same in the step F5, the PMV 21 
is fully closed (step F8). 
It is checked if an operation mode is requested from the indoor unit 
C.sub.2 (step F9). 
If so, it is checked if the operation mode is the same as the 
above-determined operation mode (step F10). If so, the operation start 
command is sent to the indoor unit C.sub.2 (step F11) and the opening of 
the PMV 31 is controlled according to the power level requested by the 
indoor unit C.sub.2 (step F12). 
If an operation mode is not requested from the indoor unit C.sub.2 in the 
step F9 or the operation mode is not the same in the step F10, the PMV 31 
is fully closed (step F13). 
It is checked if an operation mode is requested from the indoor unit 
C.sub.3 (step F14). 
If so, it is checked if the operation mode is the same as the 
above-determined operation mode (step F15). If so, the operation start 
command is sent to the indoor unit C3 (step F16) and the opening of the 
PMV 41 is controlled according to the power level requested by the indoor 
unit C.sub.3 (step F17). 
If an operation mode is not requested from the indoor unit C.sub.3 in the 
step F14 or the operation mode is not the same in the step F15, the PMV 41 
is fully closed (step F18). 
The total sum of the power levels requested from the indoor units C.sub.1 
through C.sub.3 is commanded to the out door unit A (step F19). 
Therefore, if the cooling operation mode is requested from the indoor units 
C.sub.1 through C.sub.3, the cooling operation mode is determined and 
refrigerant flows in the direction of the arrow shown by a continuous line 
in FIG. 1. 
That is, the refrigerant discharged from the compressors 1 and 2 enters the 
outdoor heat exchanger 6 through the check valves 3 and 4 and the four-way 
valve 5. The refrigerant is condensed in the outdoor heat exchanger 6. 
The refrigerant through the outdoor heat exchanger 6 passes through the 
check valve 7, liquid tank 8, header 9, PMVs 21, 31, and 41, and the 
expansion valves 22, 32, and 42 before entering the indoor heat exchangers 
24, 34, and 44 in which the refrigerant is evaporated. 
The refrigerant through the indoor heat exchangers 24, 34, and 44 passes 
through the header 11, four-way valve 5, and the accumulator 12 and is 
taken in by the compressors 1 and 2. 
In the cooling operation mode, the compressor 1 and/or compressor 2 are 
operated and the operation frequencies are controlled according to the 
total sum of the cooling power levels requested from the indoor units 
C.sub.1 through C.sub.3. 
As the total sum of the requested cooling power levels increases, the 
number of compressors operated changes from 1 to 2. On the contrary, as 
the total sum of the requested cooling power levels decreases, the number 
of compressors operated changes from 2 to 1. 
At the same time, the quantity of the refrigerant given to the indoor unit 
C.sub.1 is set according to the cooling power level requested from the 
indoor unit C.sub.1 by controlling the opening control of the PMV 21. 
The quantity of the refrigerant given to the indoor unit C.sub.2 is set 
according to the cooling power level requested from the indoor unit 
C.sub.2 by controlling the opening of the PMV 31. 
The quantity of the refrigerant given to the indoor unit C.sub.3 is set 
according to the cooling power level requested from the indoor unit 
C.sub.3 by controlling the opening of the PMV 41. 
The degree of superheat of the refrigerant in the indoor heat exchangers 
24, 34, and 44 is respectively kept at a certain value by controlling the 
flow rate of the expansion valves 22, 32, and 42. 
If the heating operation mode is requested from the indoor units C.sub.1 
through C.sub.3, the heating operation mode is determined and refrigerant 
flows in the direction of the arrow shown by a broken line in FIG. 1. 
That is, the refrigerant discharged from the compressors 1 and 2 passe 
through the check valves 3 and 4, the four-way valve 5, and the header 11 
before entering the indoor heat exchangers 24, 34, and 44 in which the 
refrigerant is condensed. 
The refrigerant through the indoor heat exchangers 24, 34, and 44 passes 
through the check valves 23, 33, and 43, the expansion valves 21, 31, and 
41, the header 9, the liquid tank 8, and the expansion valve 10 before 
entering the outdoor heat exchanger 6 in which the refrigerant is 
evaporated. 
The refrigerant through the outdoor heat exchanger 6 passes through the 
four-way valve 5 and the accumulator 12 and is taken in by the compressors 
1 and 2. 
In the heating operation mode the compressor 1 and/or compressor 2 being 
operated and the operation frequency of one or both compressors are 
controlled according to the total sum of the heating power levels 
requested from the indoor units C.sub.1 through C.sub.3. 
That is, as the total sum of the requested heating power levels increases, 
the number of compressors operated changes from 1 to 2. On the contrary, 
as the total sum of the requested heating power levels decreases, the 
number of compressors operated changes from 2 to 1. 
At the same time, the quantity of the refrigerant given to the indoor unit 
C.sub.1 is set according to the heating power level requested from the 
indoor unit C.sub.1 by controlling the opening control of the PMV 21. 
The quantity of the refrigerant given to the indoor unit C.sub.2 is set 
according to the heating power level requested from the indoor unit 
C.sub.2 by controlling the opening of the PMV 31. 
The quantity of the refrigerant given to the indoor unit C.sub.3 is set 
according to the heating power level requested from the indoor unit 
C.sub.3 by controlling the opening of the PMV 41. 
The degree of superheat of the refrigerant in the outdoor heat exchanger 6 
is kept at a certain value by controlling the flow rate of the expansion 
valve 10. 
To install the air conditioning apparatus in a building, it is necessary to 
check if the refrigerant tubes and signal conductors S.sub.1 through 
S.sub.3 are normally connected between the outdoor unit A and the indoor 
units C.sub.1 through C.sub.3, especially between the branch unit B and 
the indoor units C.sub.1 through C.sub.3. 
In this case, the checking switch 54 of the outdoor unit A is turned on by 
the operator. 
When the checking switch 54 is turned on, the checking signal is sent from 
the outdoor unit A to the branch unit B. 
When the checking signal is input to the branch controller 60 (step F1), 
the check mode routine is executed by the branch controller 60 (step F20). 
FIGS. 8A through 8D show the check mode routine. 
In the check mode routine, the timer 61 is set (step F21) and the operation 
stop command is given to the indoor units C.sub.1 through C.sub.3 (step 
F22). 
The timer 61 counts a certain time (e.g. "t" minutes) to prevent the 
compressors 1 and 2 from restarting. This restarting prevention is 
executed to prevent the service life of the compressors 1 and 2 from being 
shortened. 
When "t" minutes set in the timer 61 elapse (step F23), the PMV 21 is set 
to the opening corresponding to the capacity of the indoor unit C.sub.1 
(capacity equivalent to that of the indoor heat exchanger 24) (step F24). 
The PMVs 31 and 41 are fully closed (step F25). 
At the same time, the checking signal is sent from the branch controller 60 
to the indoor units C.sub.1 through C.sub.3 (step F26). 
The cooling operation start command is given to the outdoor unit A from the 
branch controller 60 and the prescribed power level is commanded to it 
(step F27). 
In the outdoor unit A, the compressors 1 and 2 are operated at the 
prescribed power level according to the command from the branch controller 
60 to start the cooling operation. At the same time, the command 
indicating "under operation" is given to the branch controller 60 from the 
outdoor unit A. 
When the cooling operation is started, refrigerant flows through the indoor 
heat exchanger 24. 
In this case, if the indoor unit C.sub.1 is normally connected, the 
temperature of the indoor heat exchanger 24 decreases to a certain value 
or lower and the release signal is output from the indoor controller 70. 
The release signal is sent to the branch controller 60 through the signal 
conductor S.sub.1. In the branch controller 60, reception of the "under 
operation" command is monitored (step F28). 
When the "under operation" command is given to the branch controller 60, 
the timer 62 is set to "M" minutes (e.g. 10 min). The "M" minutes are the 
duration required from the time the operation starts to the time the 
refrigerator condition is stabilized. 
At the same time, reception of the release signal from the indoor units 
C.sub.1 through C.sub.3 is monitored (steps F30, F31, and F33). 
In this case, when the release signal is received from the indoor unit 
C.sub.1, the step F37 starts. 
However, if the release signal is received from the indoor unit C.sub.2 
instead of C.sub.1, it is judged that the indoor units C.sub.1 and C.sub.2 
are abnormally connected (step F32) and the step F37 starts. 
If the release signal is received from the indoor unit C.sub.3 instead of 
C.sub.1, it is judged that the indoor units C.sub.1 and C.sub.3 are 
abnormally connected (step F35) and the step F37 starts. 
If "M" minutes elapse before the release signal is received from any indoor 
unit (step F35), it is judged that the indoor unit C.sub.1 is abnormally 
connected (step F36) and the step F37 starts. 
In the step F37, it is checked if the indoor unit C.sub.2 is judged to be 
abnormal. 
If so, the step F51 starts. 
If not, the PMV 31 is set to the opening proportional to the capacity of 
the indoor unit C.sub.2 (capacity equivalent to that of the indoor heat 
exchanger 24) (step F38). 
The current states of the PMVs 21 and 41 are maintained (step F39). 
The timer 62 is set to "N" minutes (e.g. 5 min) (step F40). 
The "N" minutes are shorter than said "M" minutes. 
Moreover, the timer 63 is set to 30 sec (step F41). When 30 sec of the 
timer elapse (step F42), the PMV 21 is fully closed (step F43). 
In this case, if the indoor unit C.sub.2 is normally connected, refrigerant 
flows through the indoor heat exchanger 34. Thus, the temperature of the 
indoor heat exchanger 34 decreases to a certain value or lower and the 
release signal is output from the indoor controller 80. The release signal 
is sent to the branch controller 60 through the signal conductor S.sub.2. 
In the branch controller 60, reception of the release signal from the 
indoor units C.sub.1 through C.sub.3 is monitored (steps F44, F45, and 
F47). 
In this case, when the release signal is received from the indoor unit 
C.sub.1, the step F51 starts. 
However, if the release signal is received from the indoor unit C.sub.1 
instead of C.sub.2, it is judged that the indoor units C.sub.1 and C.sub.2 
are abnormally connected (step F46) and the step F51 starts. 
If the release signal is received from the indoor unit C.sub.3 instead of 
C.sub.2, it is judged that the indoor units C.sub.2 and C.sub.3 are 
abnormally connected (step F48) and the step F51 starts. 
If "N" minutes elapse before the release signal is received from any indoor 
unit (step F49), it is judged that the indoor unit C.sub.2 is abnormally 
connected (step F50) and the step F51 starts. 
In the step F51, it is checked if the indoor unit C.sub.3 is judged to be 
abnormal. 
If so, the step F65 starts. 
If not, the PVM 31 is set to the opening proportional to the capacity of 
the indoor unit C.sub.3 (capacity equivalent to that of the indoor heat 
exchanger 34) (step F52). 
The current states of the PMVs 21 and 31 are maintained (step F53). 
Then, the timer 62 is set to "N" minutes (step F54). 
Moreover, the timer 63 is set to 30 sec (step F55). 
When 30 sec of the timer elapse (step F56), the PMV 31 is fully closed 
(step F57). 
In this case if the indoor unit C.sub.3 is normally connected, refrigerant 
flows through the indoor heat exchanger 44. Thus, the temperature of the 
indoor heat exchanger 44 decreases to a certain value or lower and the 
release signal is output from the indoor controller 90. The release signal 
is sent to the branch controller 60 through the signal conductor S.sub.3. 
In the branch controller 60, reception of the release signal from the 
indoor units C.sub.1 through C.sub.3 is monitored (steps F58, F59, and 
F61). 
In this case, when the release signal is received from the indoor unit 
C.sub.3, the step F65 starts. 
However, if the release signal is received from the indoor unit C.sub.1 
instead of C.sub.3, it is judged that the indoor units C.sub.1 and C.sub.3 
are abnormally connected (step F60) and the step F65 starts. 
If the release signal is received from the indoor unit C.sub.2 instead of 
C.sub.3, it is judged that the indoor units C.sub.2 and C.sub.3 are 
abnormally connected (step F62) and the step F65 starts. 
If "N" minutes elapse before the release signal is received from any indoor 
unit (step F63), it is judged that the indoor unit C.sub.3 is abnormally 
connected (step F64) and the step F65 starts. 
In the step 65, the PMV 41 is fully closed. 
If any unit is judged to be abnormal, the error contents are commanded by 
the outdoor unit A (step F66). Then the end signal indicating the end of 
checking is sent to the outdoor unit A from the branch controller 60 (step 
F67). 
In the outdoor unit A, the error contents are displayed on the indicator 
54. 
Therefore, it is possible to automatically, quickly, and accurately check 
if the refrigerant tubes and signal conductors S.sub.1 through S.sub.3 are 
normally connected between the outdoor unit A and the indoor units C.sub.1 
through C.sub.3, especially between the branch unit B and the indoor units 
C.sub.1 through C.sub.3. Thus, the operator's load is decreased and proper 
operation is realized after installation. 
Especially, because the compressors 1 and 2 are stopped for "t" minutes 
before checking is started, the following effect is expected. That is, 
even if normal operation for air conditioning is executed before checking, 
the operation does not affect the checking. 
Moreover, the service life of the refrigeration cycle parts is improved 
because the checking time for the first indoor unit is set to "M" minutes 
which are necessary for the refrigeration cycle condition to be 
stabilized. 
Therefore when checking the second indoor unit forward, there is the 
advantage that the checking time is greatly decreased because it is set to 
"N" minutes which are necessary for the refrigerator condition to be 
stabilized. 
If the release signal is output from any one of the indoor units C.sub.1 
through C.sub.3 during checking, the refrigerant flow to the indoor units 
C.sub.1 through C.sub.3 is forcibly changed regardless of the above "M" 
and "N" minutes. Therefore, also from this point of view, the checking 
time is greatly decreased. 
The following is the description of the second embodiment of the present 
invention. 
The refrigeration cycle has the same configuration as that of the first 
embodiment in FIG. 1. 
The control circuit superficially has the same configuration as that of the 
first embodiment in FIG. 2. 
However, the check mode routines of the outdoor controller 50 and the 
branch controller 60 are different from those of the first embodiment. 
FIG. 9 shows the check mode routine of the outdoor controller 50 and FIGS. 
10A through 10D show the check mode routine of the branch controller 60. 
For the control by the outdoor controller 50, the step E15' is included in 
the check mode routine. Therefore, only the step E15' is different from 
the step in the check mode routine of the first embodiment. 
That is, though the compressor 1 and/or compressor 2 being operated and the 
operation frequency of one or both compressors are set according to the 
power level requested from branch unit B in the step E15 of the first 
embodiment, they are controlled according to the outdoor air temperature 
detected by the temperature sensor 55 in the step E15' of the second 
embodiment. 
For example, if the outdoor air temperature rises, both the compressors 1 
and 2 are operated and a high operation frequency is set to show high 
power level. If the outdoor air temperature lowers, either compressor 1 or 
2 is operated and a low operation frequency is set to show lower power 
level. 
For the control by the branch controller 60, the step F27' is included in 
the check mode routine. Therefore, only the step F27' is different from 
the steps in the check mode routine of the first embodiment. 
That is, though the start of the cooling operation and the prescribed power 
level are commanded by the outdoor unit A in the step F27 of the first 
embodiment, only the start of the cooling operation is commanded by the 
outdoor unit A in the step F27' of the second embodiment. 
Thus, it is possible to prevent the compressors 1 and 2 from being 
overloaded by controlling the power levels of the compressors 1 and 2 
according to the outdoor air temperature for checking. Therefore, there is 
the advantage that the durability and reliability of the compressors 1 and 
2 are improved in addition to the effect of the first embodiment. 
Then, the third embodiment of the present invention is described below. 
The refrigeration cycle has the same configuration as that of the first 
embodiment in FIG. 1. The control circuit superficially has the same 
configuration as that of the first embodiment in FIG. 2. 
However, the check mode routines of the outdoor controller 50 and the 
branch controller 60 are different from those in the first embodiment. 
FIGS. 11A and 11B shows the check mode routine of the outdoor controller 
50. FIGS. 12A through 12D shows the check mode routine of the branch 
controller 60. 
The check mode routine of the outdoor controller 50 is described according 
to FIGS. 11A and 11B. 
In the check mode routine, the compressors 1 and 2 are stopped (step H1) 
and the outdoor fan 16 is stopped (step H2). At the same time, the 
checking signal and data for the outdoor air temperature T detected by the 
temperature sensor 55 are sent to the branch unit B (step H3). 
When the cooling operation start command is given from the branch unit B 
(step H4), the four-way valve 5 is not operated (step H5) and the step H8 
starts. 
When the heating operation start command is given from the branch unit B 
(step H6), the four-way valve 5 is not operated (step H7) and the step H8 
starts. 
In the step H8, the compressors 1 and/or 2 are operated. Also, the 
compressor 1 and/or compressor 2 being operated and the operation 
frequency of one or both compressors are controlled according to the power 
level requested from the branch unit B. 
At the same time, the outdoor fan 16 is operated according to necessity 
(step H9). 
When the operation is started, the "under operation" command is given to 
the branch unit B (step H10). 
When the error command is given from the branch unit B (step H11), the 
error contents to be commanded from the branch unit B are displayed on the 
indicator 54 (step H12). 
When the end signal is given from the branch unit B (step H13), the 
compressors 1 and 2 are stopped (step H14) and the outdoor fan 16 is 
stopped (step H15). At the same time, the four-way valve 5 is stopped 
(step H16). 
The check mode routine of the branch controller 60 is described below 
according to FIGS. 12A through 12D. 
In the check mode routine, the timer 61 is set (step I21), the outdoor air 
temperature T is detected according to the data sent from the outdoor unit 
A (step I2), and the operation stop command is given to the indoor units 
C.sub.1 through C.sub.3 (step I3). 
When "t" minutes set in the timer 61 elapse (step I4), the PMV 21 is set to 
the opening corresponding to the capacity of the indoor unit C.sub.1 
(capacity equivalent to that of the indoor heat exchanger 24). The PMVs 31 
and 41 are fully closed. 
At the same time, the checking signal is sent from the branch controller 60 
to the indoor units C.sub.1 through C.sub.3 (step I6). 
The outdoor air temperature T is compared with the previously-set value Ts 
(step I7). 
If a temperature T is higher than the set value Ts, the cooling operation 
start command is given from the branch controller 60 to the outdoor unit A 
(step I8) and the prescribed power level is commanded (step I9). 
In this case, in the outdoor unit A, the compressors 1 and 2 are operated 
at the prescribed power level according to the command from the branch 
controller 60 and the cooling operation is started. At the same time, the 
"under operation" command is given from the outdoor unit A to the branch 
controller 60. 
When the cooling operation is started, refrigerant flows through the indoor 
heat exchanger 24. 
In this case, if the indoor unit C.sub.1 is normally connected, the 
temperature of the indoor heat exchanger 24 decreases to a certain value 
or lower and the release signal is output from the indoor controller 70. 
The release signal is sent to the branch controller 60 through the signal 
conductor S.sub.1. 
If the temperature T is lower than the set value Ts, the heating operation 
start command is given from the branch controller 60 to the outdoor unit A 
(step I10) and the prescribed power level is commanded (step I11). 
In this case, in the outdoor unit A, the compressors 1 and 2 are operated 
at the prescribed power level according to the command from the branch 
controller 60, the four-way valve 5 is operated, and the heating 
operations is started. At the same time, the "under operation" command is 
given from the outdoor unit A to the branch controller 60. 
When the heating operation is started, refrigerant flows through the indoor 
heat exchanger 24. 
In this case, if the indoor unit C.sub.1 is normally connected, the 
temperature of the indoor heat exchanger 24 increases to a certain value 
or higher and the release signal is output from the indoor controller 70. 
The release sign is sent to the branch controller 60 through the signal 
conductor S.sub.1. 
In the branch controller 60, reception of "under operation" command is 
monitored (step I12). 
If the "under operation" command is given to the branch controller 60, the 
timer 62 is set to "M" minutes (e.g. 10 min). The "M" minutes are the 
adequate duration required from the time the operation starts to the time 
the refrigeration cycle condition is stabilized. 
At the same time, reception of the release signal from the indoor units 
C.sub.1 through C.sub.3 is monitored (steps I14, I15, and I17). 
In this case, if the release signal is received from the indoor unit 
C.sub.1, the step I21 starts 
However, if the release signal is received from the indoor unit C.sub.2 
instead of C.sub.1, it is judged that the indoor units C.sub.1 and C.sub.3 
are abnormally connected (step I18) and the step I21 starts. 
If "M" minutes elapse before the release signal is received from any indoor 
unit (step I19), it is judged that the indoor unit C.sub.1 is abnormally 
connected (step I20) and the step I21 starts. 
In the step I21, it is checked if the indoor unit C.sub.2 is judged to be 
abnormal. 
If so, the step I35 starts. 
If not, the PMV 31 is set to the opening proportional to the capacity of 
the indoor unit C.sub.2 (capacity equivalent to that of the indoor heat 
exchanger 24) (step I22). 
The current states of the PMVs 21 and 41 are maintained (step I23). 
The timer 62 is set to "N" minutes (e.g. 5 min) (step I24). The "N" minutes 
are shorter than the above "M" minutes. Also, the timer 63 is set to 30 
sec (step I25). 
When 30 seconds set in the timer 63 elapse (step I26), the PMV 21 is fully 
closed (step I27). 
In this case, if the indoor unit C.sub.2 is normally connected, refrigerant 
flows through the indoor heat exchanger 34. Thus, the temperature of the 
indoor heat exchanger 34 increases to a certain value o higher and the 
release signal is output from the indoor controller 80. The release signal 
is sent to the branch controller 60 through the signal conductor S.sub.2. 
In the branch controller 60, reception of the release signal from the 
indoor units C.sub.1 through C.sub.3 is monitored (steps I28, I29, and 
I31). 
In this case, if the release signal is received from the indoor unit 
C.sub.1, the step I35 starts. 
However, if the release signal is received from the indoor unit C.sub.1 
instead of C.sub.2, it is judged that the indoor units C.sub.1 and C.sub.2 
are abnormally connected (step I30) and the step I35 starts. 
If the release signal is received from the indoor unit C.sub.3 instead of 
C.sub.2, it is judged that the indoor units C.sub.2 and C.sub.3 are 
abnormally connected (step I32) and the step I35 starts. 
If "N" minutes elapse before the release signal is received from any indoor 
unit (step I33), it is judged that the indoor unit C.sub.2 is abnormally 
connected (step I34) and the step I35 starts. 
In the step I35, it is checked if the indoor unit C.sub.3 is judged to be 
abnormal. 
If so, the step I49 starts. 
If not, the PMV 31 is set to the opening proportional to the capacity of 
the indoor unit C.sub.3 (capacity equivalent to that of the indoor heat 
exchanger 34) (step I36). 
The current states of the PMVs 21 and 31 are maintained (step I37). 
The timer 62 is set to "N" minutes (step I38). Also, the timer 63 is set to 
30 sec (step I39). When 30 seconds set in the timer 63 elapse (step I40), 
the PMV 31 is fully closed (step I41). 
In this case, if the indoor unit C.sub.3 is normally connected, refrigerant 
flows through the indoor heat exchanger 44. Thus, the temperature of the 
indoor heat exchanger 44 increases to a certain value or higher and the 
release signal is output from the indoor controller 90. The release signal 
is sent to the branch controller 60 through the signal conductor S.sub.3. 
In the branch controller 60, reception of the release signal from the 
indoor units C.sub.1 through C.sub.3 is monitored (steps I42, I43, and 
I45). 
In this case, if the release signal is received from the indoor units 
C.sub.3, the step I49 starts. 
However, if the release signal is received from the indoor unit C.sub.1 
instead of C.sub.3, it is judged that the indoor units C.sub.1 and C.sub.3 
are abnormally connected (step I44) and the step I49 starts. 
If the release signal is received from the indoor unit C.sub.2 instead of 
C.sub.3, it is judged that the indoor units C.sub.2 and C.sub.3 are 
abnormally connected (step I46) and the step I49 starts. 
If "N" minutes elapse before the release signal is received from any indoor 
unit (step I47), it is judged that the indoor unit C.sub.3 is abnormally 
connected (step I48) and the step I49 starts. 
In the step I49, the PMV 41 is fully closed. 
If any unit is judged to be abnormal, the error contents are commanded to 
the outdoor unit A (step I50). Then, the signal indicating the end of 
checking is sent from the branch controller 60 to the outdoor unit A (step 
I51). 
In the outdoor unit A, the error contents are displayed on the indicator 
54. 
Therefore, it is possible to automatically, quickly, and accurately check 
if the refrigerant tubes and signal conductors S.sub.1 through S.sub.3 are 
normally connected between the outdoor unit A and the indoor units C.sub.1 
through C.sub.3, especially between the branch unit B and the indoor units 
C.sub.1 through C.sub.3. Thus, the operator's load is decreased and proper 
operation is realized after installation. 
Especially, because the compressors 1 and 2 are stopped for "t" minutes 
before checking is started, the following effect is expected. That is, 
even if normal operation for air conditioning is executed before checking, 
the operation does not affect the checking. 
Moreover, the service life of the refrigeration cycle parts is improved 
because the checking time for the first indoor unit is set to "M" minutes 
which are necessary for the refrigeration cycle condition to be 
stabilized. 
Therefore, when checking the second indoor unit forward, there is the 
advantage that the checking time is greatly decreased because it is set to 
"N" minutes which are necessary for the refrigerator condition to be 
stabilized. 
If the release signal is output from any one of the indoor units C.sub.1 
through C.sub.3 during checking, the refrigerant flow to the indoor units 
C.sub.1 through C.sub.3 is forcibly changed regardless of the above "M" 
and "N" minutes. Therefore, also from this point of view, the checking 
time is greatly decreased. 
It is also possible to prevent the compressors 1 and 2 from being 
overloaded because the cooling or heating operation is selectively 
executed for checking according to the outdoor air temperature T. 
Therefore, the durability of the compressors 1 and 2 is improved. 
The following is the description of the fourth embodiment of the present 
invention. 
The refrigeration cycle has the same configuration as that of the first 
embodiment in FIG. 1. 
The control circuit superficially has the same configuration as that of the 
first embodiment in FIG. 2. 
However, the check mode routines of the outdoor controller 50 and the 
branch controller 60 are different from those of the first embodiment. 
The check mode routine of the outdoor controller 50 is the same as that of 
the third embodiment in FIGS. 11A and 11B. 
The check mode routine of the branch controller 6 is shown in FIGS. 13A 
through 13E, which is described below. 
The timer 61 is set (step J1). The flag F is set to "0" (step J2), which 
memorizes whether or not the cooling operation is executed. The operation 
stop command is given to the indoor units C.sub.1 through C.sub.3 (step 
J3). 
When "t" minutes set in the timer 61 elapse (step J4), the PMV 21 is set to 
the opening corresponding to the capacity of the indoor unit C.sub.1 
(capacity equivalent to that of the indoor heat exchanger 24) (step J5). 
The PMVs 31 and 41 are fully closed. 
At the same time, the checking signal is sent from the branch controller 60 
to the indoor units C.sub.1 through C.sub.3 (step J6). 
It is checked if the flag F is set to "0" (step J7). 
In this case, because the flag F is set to "0", the cooling operation start 
command is given from the branch controller 60 to the outdoor unit A (step 
J8) and the prescribed power level is commanded (step J9). 
In this case, in the outdoor unit A, the compressors 1 and 2 are operated 
at the prescribed power level according to the command from the branch 
controller 60 to start the cooling operation. At the same time, the "under 
operation" command is given from the outdoor unit A to the branch 
controller 60. 
When the cooling operation is started, refrigerant flows through the indoor 
heat exchanger 24. 
In this case, if the indoor unit C.sub.1 is normally connected, the 
temperature of the indoor heat exchanger 24 decreases to a certain value 
or lower and the release signal is output form the indoor controller 70. 
The release signal is sent to the branch controller 60 through the signal 
conductor S.sub.1. 
In the branch controller 60, reception of the "under operation" command is 
monitored (step J12). When the "under operation" command is given to the 
branch controller 60, the timer 62 is set to "M" minutes (e.g. 10 min) 
(step J13). The "M" minutes is the adequate duration required from the 
time the operation starts to the time the refrigeration cycle condition is 
stabilized. 
At the same time, reception of the release signal from the indoor units 
C.sub.1 through C.sub.3 is monitored (steps J14, J15, and J17). 
In this case, if the release signal is received from the indoor unit 
C.sub.1, the step J21 starts. 
However, if the release signal is received from the indoor unit C.sub.2 
instead of C.sub.1, it is judged that the indoor units C.sub.1 and C.sub.2 
are abnormally connected (step J16) and the step J21 starts. 
If the release signal is received from the indoor unit C.sub.3 instead of 
C.sub.1, it is judged that the indoor units C.sub.1 and C.sub.3 are 
abnormally connected (step J18) and the step J21 starts. 
If "M" minutes elapse before the release signal is received from any indoor 
unit (step J19), it is judged that the indoor unit C.sub.1 is abnormally 
connected (step J20) and the step J21 starts. 
In the step J21, it is checked if the indoor unit C.sub.2 is judged to be 
abnormal. 
If so, the step J35 starts. 
If not, the PMV 31 is set to the opening proportional to the capacity of 
the indoor unit C.sub.2 (capacity equivalent to that of the indoor heat 
exchanger 34) (step J22). 
The current states of the PMVs 21 and 41 are maintained (step J23). 
The timer 62 is set to "N" minutes (e.g. 5 min) (step J24). The "N" minutes 
are shorter than the above "M" minutes. Also, the timer 63 is set to 30 
sec (step J25). When 30 seconds set in the timer 63 elapse (step J26), the 
PMV 21 is fully closed (step J27). 
In this case, if the indoor unit C.sub.2 is normally connected, refrigerant 
flows through the indoor heat exchanger 34. Thus, the temperature of the 
indoor heat exchanger 34 increases to a certain value or higher and the 
release signal is output from the indoor controller 80. The release signal 
is sent to the branch controller 60 through the signal conductor S.sub.2. 
In the branch controller 60, reception of the release signal from the 
indoor units C.sub.1 through C.sub.3 is monitored (steps J28, J29, and 
J31). 
In this case, if the release signal is received from the indoor unit 
C.sub.1, the step J35 starts. 
However, if the release signal is received from the indoor unit C.sub.1 
instead of C.sub.2, it is judged that the indoor units C.sub.1 and C.sub.2 
are abnormally connected (step J30) and the step J35 starts. 
If the release signal is received from the indoor unit C.sub.3 instead of 
C.sub.2, it is judged that the indoor units C.sub.2 and C.sub.3 are 
abnormally connected (step J32) and the step J35 starts. 
If "N" minutes elapse before the release signal is received from any indoor 
unit (step J33), it is judged that the indoor unit C.sub.3 is abnormally 
connected (step J34) and the step J35 starts. 
In the step J35, it is checked if the indoor unit C.sub.3 is judged to be 
abnormal. 
If so, the step J49 starts. 
If not, the PMV 31 is set to the opening proportional to the capacity of 
the indoor unit C.sub.3 (capacity equivalent to that of the indoor heat 
exchanger 34) (step J36). 
The current states of the PMVs 21 and 31 are maintained (step J37). 
And the timer 62 is set to "N" minutes (step J38). 
Moreover, the timer 63 is set to 30 sec (step J39). 
When 30 sec set in the timer 63 elapse (step J40), the PMV 31 is fully 
closed (step J41). 
In this case, if the indoor unit C.sub.3 is normally connected, refrigerant 
flows through the indoor heat exchanger 44. Thus, the temperature of the 
indoor heat exchanger 44 increases to a certain value or higher and the 
release signal is output from the indoor controller 90. The release signal 
is sent to the branch controller 60 through the signal conductor S.sub.3. 
In the branch controller 60, reception of the release signal from the 
indoor units C.sub.1 through C.sub.3 is monitored (steps J42, J43, and 
J45). 
In this case, if the release signal is received from the indoor unit 
C.sub.3, the step J49 starts. 
However, if the release signal is received from the indoor unit C.sub.1 
instead of C.sub.3, it is judged that the indoor units C.sub.1 and C.sub.3 
are abnormally connected (step J44) and the step J49 starts. 
If the release signal is received from the indoor unit C.sub.2 instead of 
C.sub.3, it is judged that the indoor units C.sub.2 and C.sub.3 are 
abnormally connected (step J46) and the step J49 starts. 
If "N" minutes elapse before the release signal is received from any indoor 
unit (step J47), it is judged that the indoor unit C.sub.3 is abnormally 
connected (step J48), the step J49 starts. 
In the step J49, the PMV 41 is fully closed. 
It is checked if the flag F is set to "1" (step J50). 
In this case, the flag F is still set to "0". Therefore, the flag F is set 
to "1" (step J51). 
Then, the step J3 starts. 
Because the flag F is set to "1" in the step J7, the heating operation 
command is given from the branch controller 60 to the outdoor unit A (step 
J10) and the prescribed power level is commanded (step J11). 
In this case, in the outdoor unit A, the compressors 1 and 2 are operated 
at the prescribed power level according to the command from the branch 
controller 60 and the four-way valve 5 is operated to start the heating 
operation. 
Thus, the same checking is repeated during the heating operation. 
When the checking for the heating operation is completed, final judgment is 
executed. 
If the indoor unit C.sub.1 is judged to be abnormal for both the cooling 
and heating operations (step J52), it is finally judged that the indoor 
unit C.sub.1 is abnormally connected (step J53). 
Unless the indoor unit C.sub.1 is judged to be abnormal for the cooling 
operation and the heating operation, it is finally judged that the indoor 
unit C.sub.1 is normally connected (step J54). 
If the indoor unit C.sub.2 is judged to be abnormal for both the cooling 
and heating operations (step J55), it is finally judged that the indoor 
unit C.sub.2 is abnormally connected (step J56). 
Unless the indoor unit C.sub.2 is judged to be abnormal for the cooling 
operation and the heating operation, it is finally judged that the indoor 
unit C.sub.2 is normally connected (step J57). 
If the indoor unit C.sub.3 is judged to be abnormal for both the cooling 
and heating operations (step J58), it is finally judged that the indoor 
unit C.sub.3 is abnormally connected (step J59). 
Unless the indoor unit is judged to be abnormal for the cooling operation 
and heating operation, it is finally judged that the indoor unit C.sub.3 
is normally connected (step J60). 
If any unit is finally judged to be abnormal, the error contents are 
commanded to the outdoor unit A step J61). Then, the signal indicating the 
end of checking is sent from the branch controller 60 to the outdoor unit 
A (step J62). 
In the outdoor unit A, the error contents are displayed on the indicator 
54. 
Therefore, it is possible to automatically, quickly, and accurately check 
if the refrigerant tubes and signal conductors S.sub.1 through S.sub.3 are 
normally connected between the outdoor unit A and indoor units C.sub.1 
through C.sub.3, especially between the branch unit B and the indoor units 
C.sub.1 through C.sub.3. Thus, the operator's load is decreased and proper 
operation is realized after installation. 
Especially, because the compressors 1 and 2 are stopped for "t" minutes 
before checking is started, the following effect is expected. That is, 
even if the normal operation for air conditioning is executed before 
checking, the operation does not affect the checking. 
Moreover, the service life of the refrigeration cycle parts is improved 
because the checking time for the first indoor unit is set to "M" minutes 
which are necessary for the refrigeration cycle condition to be 
stabilized. 
Therefore, when checking the second indoor unit forward, there is the 
advantage that the checking time is greatly decreased because it is set to 
"N" minutes which are necessary for the refrigerator condition to be 
stabilized. 
If the release signal is output from any one of the indoor units C.sub.1 
through C.sub.3 during checking, the refrigerant flow to the indoor units 
C.sub.1 through C.sub.3 is forcibly changed regardless of the above "M" 
and "N" minutes. Therefore, also from this point of view, the checking 
time is greatly decreased. 
Moreover, because indoor units are checked for both the cooling and heating 
operations, it is possible to prevent erroneous judgment due to the 
influence of outdoor and indoor air temperatures. Therefore, the checking 
reliability is improved. 
In this fourth embodiment, the cooling operation is executed before the 
heating operation for checking. However, it is also permitted to execute 
the heating operation before the cooling operation. 
The following is the description of the fifth embodiment of the present 
invention. 
The refrigeration cycle has the same configuration as that of the first 
embodiment in FIG. 1. 
The control circuit superficially has the same configuration as that of the 
first embodiment in FIG. 2. 
However, the check mode routines of the outdoor controller 50 and the 
branch controller 60 are different from those of the first embodiment. 
The check mode routine of the outdoor controller 50 is the same as that of 
the third embodiment in FIGS. 11A and 11B. 
The check mode routine of the branch controller 60 is shown in FIGS. 14A 
through 14E, which is described below. 
The timer 61 is set (step K1). The flag F is set to "0" (step K2), which 
memorizes whether or not the cooling operation is executed. The operation 
stop command is given to the indoor units C.sub.1 through C.sub.3 (step 
K3). 
When "t" minutes set in the timer 61 elapse (step K4), the PMV 21 is set to 
the opening corresponding to the capacity of the indoor unit C.sub.1 
(capacity equivalent to that of the indoor heat exchanger 24) (step K5). 
The PMVs 31 and 41 are fully closed. 
At the same time, the checking signal is sent from the branch controller 60 
to the indoor units C.sub.1 through C.sub.3 (step K6). 
It is checked if the flag F is set to "0" (step K7). 
In this case, because the flag F is set to "0", the cooling operation start 
command is given from the branch controller 60 to the outdoor unit A (step 
K8) and the prescribed power level is commanded (step K9). 
In this case, in the outdoor unit A, the compressors 1 and 2 are operated 
at the prescribed power level according to the command from the branch 
controller 60 to start the cooling operation. At the same time, the "under 
operation" command is given from the outdoor unit A to the branch 
controller 60. When the cooling operation is started, refrigerant flows 
through the indoor heat exchanger 24. 
In this case, if the indoor unit C.sub.1 is normally connected, the 
temperature of the indoor heat exchanger 24 decreases to a certain value 
or lower and the release signal is output from the indoor controller 70. 
The release signal is sent to the branch controller 60 through the signal 
conductor S.sub.1. 
In the branch controller 60, reception of the "under operation" command is 
monitored (step K12). When the "under operation" command is given to the 
branch controller 60, the timer 62 is set to "M" minutes (e.g. 10-min) 
(step K13). The "M" minutes is the adequate duration required from the 
time the operation starts to the time the refrigeration cycle condition is 
stabilized. 
At the same time, reception of the release signal from the indoor units 
C.sub.1 through C.sub.3 is monitored (steps K14, K15, and K17). 
In this case, if the release signal is received from the indoor unit 
C.sub.1, the step K21 starts. 
However, if the release signal is received from the indoor unit C.sub.2 
instead of C.sub.1, it is judged that the indoor units C.sub.1 and C.sub.2 
are abnormally connected (step K16) and the step K21 starts. 
If the release signal is received from the indoor unit C.sub.3 instead of 
C.sub.1, it is judged that the indoor units C.sub.1 and C.sub.3 are 
abnormally connected (step K18) and the step K21 starts. 
If "M" minutes elapse before the release signal is received from any indoor 
unit (step K19), it is judged that the indoor unit C.sub.1 is abnormally 
connected (step K20) and the step K21 starts. 
In the step K21, it is checked if the indoor unit C.sub.2 is judged to be 
abnormal. 
If so, the step K35 starts. 
if not, the PMV 31 is set to the opening proportional to the capacity of 
the indoor unit C.sub.2 (capacity equivalent to that of the indoor heat 
exchanger 24) (step K22). 
The current states of the PMVs 21 and 41 are maintained (step K23). 
The timer 62 is set to "N" minutes (e.g. 5 min) (step K24). Also, the timer 
63 is set to 30 seconds (step K25). When 30 seconds set in the timer 63 
elapse (step K26), the PMV 21 is fully closed (step K27). 
In this case, if the indoor unit C.sub.2 is normally connected, refrigerant 
flows through the indoor heat exchanger 34. Thus, the temperature of the 
indoor heat exchanger 34 increases to a certain value or higher and the 
release signal is output from the indoor controller 80. The release signal 
is sent to the branch controller 60 through the signal conductor S.sub.2. 
In the branch controller 60, reception of the release signal from the 
indoor units C.sub.1 through C.sub.3 is monitored (steps K28, K29, and 
K31). 
In this case, if the release signal is received from the indoor unit 
C.sub.1, the step K35 starts. 
However, if the release signal is received from the indoor unit C.sub.1 
instead of C.sub.2, it is judged that the indoor units C.sub.1 and C.sub.2 
are abnormally connected (step K30) and the step K35 starts. 
If the release signal is received from the indoor unit C.sub.3 instead of 
C.sub.2, it is judged that the indoor units C.sub.2 and C.sub.3 are 
abnormally connected (step K32) and the step K35 starts. 
If "N" minutes elapse before the release signal is received from any indoor 
unit (step K33), it is judged that the indoor unit C.sub.3 is abnormally 
connected (step K34) and the step K35 starts. 
In the step K35, it is checked if the indoor unit C.sub.3 is judged to be 
abnormal. 
If so, the step K49 starts. 
If not, the PMV 31 is set to the opening proportional to the capacity of 
the indoor unit C.sub.3 (capacity equivalent to that of the indoor heat 
exchanger 34) (step K36). 
The current states of the PMVs 21 and 31 are maintained (step K37). 
And the timer 62 is set to "N" minutes (step K38). 
Moreover, the timer 63 is set to 30 seconds (step K39). 
When 30 seconds set in the timer 63 elapse (step K40), the PMV 31 is fully 
closed (step K41). 
In this case, if the indoor unit C.sub.3 is normally connected, refrigerant 
flows through the indoor heat exchanger 44. Thus, the temperature of the 
indoor heat exchanger 44 increases to a certain value or higher and the 
release signal is output from the indoor controller 90. The release signal 
is sent to the branch controller 60 through the signal conductor S.sub.3. 
In the branch controller 60, reception of the release signal from the 
indoor units C.sub.1 through C.sub.3 is monitored (steps K42, K43, and 
K45). 
In this case, if the release signal is received from the indoor units 
C.sub.3, the step K49 starts. 
However, if the release signal is received from the indoor unit C.sub.1 
instead of C.sub.3, it is judged that the indoor units C.sub.1 and C.sub.3 
are abnormally connected (step K44) and the step K49 starts. 
If the release signal is received from the indoor unit C.sub.2 instead of 
C.sub.3, it is judged that the indoor units C.sub.2 and C.sub.3 are 
abnormally connected (step K46) and the step K49 starts. 
If "N" minutes elapse before the release signal is received from any indoor 
unit (step K47), it is judged that the indoor unit C.sub.3 is abnormally 
connected (step K48), the step K49 starts. 
In the step K49, the PMV 41 is fully closed. 
A series of judgment for the checking in the above cooling operation is 
called the first judgment. 
It is checked if any unit is judged to be abnormal throughout the first 
judgment (step K50). 
If not, the entire judgment is completed and the step K63 starts. In the 
step 63, the signal indicating the end of the checking is sent from the 
branch controller 60 to the outdoor unit A. 
If so, however, it is checked if the flag F is set to "1" (step K51). 
In this case, the flag F is still set to "0". Therefore, the flag F is set 
to "1" (step K52). 
Then, the step K3 starts. 
Because the flag F is set to "1" in the step K7, the heating operation 
command is given from the branch controller 60 to the outdoor unit A (step 
K10) and the prescribed power level is commanded (step K11). 
In this case, in the outdoor unit A, the compressors 1 and 2 are operated 
at the prescribed power level according to the command from the branch 
controller 60 and the four-way valve 5 is operated to start the heating 
operation. 
Thus, the same checking is repeated during the heating operation. 
A series of judgment for the checking in the heating operation is called 
the second judgment. 
It is checked if any unit is judged to be abnormal throughout the second 
judgment (step K50). 
If not, the entire judgment is completed and the step K63 starts. In the 
step K63, the signal indicating the end of checking is sent from the 
branch controller 60 to the outdoor unit A. 
When the checking in the heating operation is also completed, the final 
judgment is executed according to the results of the first and second 
judgment. 
That is, if the indoor unit C.sub.1 is judged to be abnormal for both the 
cooling and heating operations (step K53), it is finally judged that the 
indoor unit C.sub.1 is abnormally connected (step K54). 
Unless the indoor unit C.sub.1 is judged to be abnormal for the cooling 
operation and the heating operation, it is finally judged that the indoor 
unit C.sub.1 is normally connected (step K55). 
If the indoor unit C.sub.2 is judged to be abnormal for both the cooling 
and hating operations (step K56), it is finally judged that the indoor 
unit C.sub.2 is abnormally connected (step K57). 
Unless the indoor unit C.sub.2 is judged to be abnormal for the cooling 
operation and the heating operation, it is finally judged that the indoor 
unit C.sub.2 is normally connected (step K58). 
If the indoor unit C.sub.3 is judged to be abnormal for both the cooling 
and heating operations (step K59), it is finally judged that the indoor 
unit C.sub.3 is abnormally connected (step K60). 
Unless the indoor unit is judged to be abnormal for the cooling operation 
and heating operation, it is 
finally judged that the indoor unit C.sub.3 is normally connected (step 
K61). 
If any unit is finally judged to be abnormal, the error contents are 
commanded to the outdoor unit A (step K62). Then, the signal indicating 
the end of checking is sent form the branch controller 60 to the outdoor 
unit A (step K63). 
In the outdoor unit A, the error contents are displayed on the indicator 
54. 
Therefore, it is possible to automatically, quickly, and accurately check 
if the refrigerant tubes and signal conductors S.sub.1 through S.sub.3 are 
normally connected between the outdoor unit A and indoor units C.sub.1 
through C.sub.3, especially between the branch unit B and the indoor units 
C.sub.1 through C.sub.3. Thus, the operator's load is decreased and proper 
operation is realized after installation. 
Especially, because the compressors 1 and 2 are stopped for "t" minutes 
before checking is started, the following effect is expected. That is, 
even if the normal operation for air conditioning is executed before 
checking, the operation does not affect the checking. 
Moreover, the service life of the refrigeration cycle parts is improved 
because the checking time for the first indoor unit is set to "M" minutes 
which are necessary for the refrigeration cycle condition to be 
stabilized. 
Therefore, when checking the second indoor unit forward, there if the 
advantage that the checking time is greatly decreased because it is set to 
"N" minutes which are necessary for the refrigerator condition to be 
stabilized. 
If the release signal is output from any one of 
the indoor units C.sub.1 through C.sub.3 during checking, the refrigerant 
flow to the indoor units C.sub.1 through C.sub.3 is forcibly changed 
regardless of the above "M" and "N" minutes. Therefore, also from this 
point of view, the checking time is greatly decreased. 
Moreover, because indoor units are checked for both the cooling and heating 
operations, it is possible to prevent erroneous judgment due to the 
influence of outdoor and indoor air temperatures. Therefore, the checking 
reliability is improved. 
In this fifth embodiment, the cooling operation is executed before the 
heating operation for checking. However, it is also permitted to execute 
the heating operation before the cooling operation. 
In each of the above embodiments, description is made for the case in which 
three indoor units are used. However, the number of indoor units is 
unlimited. Therefore, four or more units can be used. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the invention in its broader aspects is not limited 
to the specific details, and representative devices, shown and described 
herein. Accordingly, various modifications may be made without departing 
from the spirit or scope of the general inventive concept as defined by 
the appended claims and their equivalents.