Midea M-Thermal A Series User manual

M-Thermal A Series Split
Commercial Air Conditioners
R32
Service
Manual
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M thermal Split
202004 1
CONTENTS
CONTENTS
Part 1 General Information ............................................................................ 3
Part 2 Component Layout and Refrigerant Circuits ..................................... 7
Part 3 Control ............................................................................................... 17
Part 4 Diagnosis and Troubleshooting ......................................................... 31
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Service Manual
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202004 3
Part 1
-
General Information
Part 1
General Information
1 Unit Capacities ........................................................................................... 4
2 External Appearance .................................................................................. 5
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1 Unit Capacities
1.1 Outdoor Unit Capacities
Table 1-1.1: Capacity range
Capacity 4kW 6kW 8kW 10kW 12kW 14kW 16kW
Model1
(MHA-*/D2N8-B)
V4W V6W V8W V10W V12W V14W V16W
Model
1
(MHA-*/D2RN8-B)
/ / / / V12W V14W V16W
Notes:
The full model names can be obtained by substituting the asterisk in the model name format given in the left-hand column of the table above with the shortened
model names given in the table. For example, the model name for the 10kW model is MHA-V10W/D2N8-B.
1.2 Hydronic Box Model
Table 1-1.2: Model
Model
1
HB-A60/CGN8-B HB-A100/CGN8-B HB-A160/CGN8-B
Compatible OU model MHA-V4(6)W/D2N8-B MHA-V8(10)W/D2N8-B MHA-V12(14,16)W/D2N8-B
MHA-V12(14,16)W/D2RN8-B
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Part 1
-
General Information
2 External Appearance
2.1 Outdoor Unit Appearance
Table 1-2.1: Outdoor unit appearance
MHA-V4(6)W/D2N8-B MHA-V8(10,12,14,16)W/D2N8
MHA-V12(14,16)W/D2RN8
2.2 Hydronic Box Appearance
Table 1-2.2: Hydronic box appearance
HB-A60/CGN8-B HB-A100/CGN8-B HB-A160/CGN8-B
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Service Manual
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M thermal Split
Part 2
-
Component Layout
and
Refrigerant Circuits
Part 2
Component Layout and
Refrigerant Circuits
1 Layout of Functional Components ......................................................... 8
2 Piping Diagrams .................................................................................. 13
3 Refrigerant Flow Diagrams .................................................................. 15
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Service Manual
1 Layout of Functional Components
1.1 Outdoor Unit Layout
MHA-V4W/D2N8-B / MHA-V6W/D2N8-B
Figure 2-1.1: MHA-V4(6)W/D2N8-B top view
Figure 2-1.2: MHA-V4(6)W/D2N8-B front view
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Part 2
-
Component Layout
and
Refrigerant Circuits
MHA-V8W/D2N8-B / MHA-V10W/D2N8-B
Figure 2-1.3: MHA-V8(10)W/D2N8-B top view
Figure 2-1.4: MHA-V8(10)W/D2N8-B front view
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Midea M thermal Split
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MHA-V12W/D2N8-B / MHA-V14W/D2N8-B / MHA-V16W/D2N8-B
Figure 2-1.5: MHA-V12(14,16)W/D2N8-B top view
Figure 2-1.6: MHA-V12(14,16)W/D2N8-B front view
10 202004
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M thermal Split
Part 2
-
Component Layout
and
Refrigerant Circuits
MHA-V12W/D2RN8-B / MHA-V14W/D2RN8-B / MHA-V16W/D2RN8-B
Figure 2-1.7: MHA-V12(14,16)W/D2RN8-B top view
Figure 2-1.8: MHA-V12(14,16)W/D2RN8-B front view
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1.2 Hydronic Box Layout
Figure 2-1.9: HB-A60(100,160)/CGN8-B oblique view
Electric control box
Expansion vessel
Manometer
Safety valve
Air purge valve
Water flow switch
Water side heat exchanger
Water pump
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Part 2 - Component Layout and
Refrigerant Circuits
2 Piping Diagrams
2.1 Outdoor Unit Piping
Figure 2-2.1: Outdoor unit piping diagram
Legend
1
Compressor
7
Electronic expansion valve
2.1 Discharge pipe temperature sensor 8 Stop valve (liquid side)
2.2
Outdoor ambient temperature sensor
9
Stop valve (gas side)
2.3 Air side heat exchanger refrigerant outlet temperature sensor 10 Pressure sensor
2.4
Suction pipe temperature sensor
11
Separator
3 4-way valve 12.1 Low pressure switch
4 Air side heat exchanger 12.2 High pressure switch
5 Distributor 13 Capillary
6 Filter 14 Solenoid valve
Key components:
1. Electronic expansion valve (EXV):
Controls refrigerant flow and reduces refrigerant pressure.
2. Four-way valve:
Controls refrigerant flow direction. Closed in cooling mode and open in heating mode. When closed, the air side heat
exchanger functions as a condenser and water side heat exchanger functions as an evaporator; when open, the air
side heat exchanger functions as an evaporator and water side heat exchanger function as a condenser.
3. High and low pressure switches:
Regulate refrigerant system pressure. When refrigerant system pressure rises above the upper limit or falls below the
lower limit, the high or low pressure switches turn off, stopping the compressor.
4. Separator:
Separates liquid refrigerant from gas refrigerant to protect compressor from liquid hammering.
Air side heat exchanger
1
3
11
4
7
14
6
2.2
2.3
8
9
12.2
12.1
10
13
2.4
5
6
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Service Manual
2.2 Hydronic box Piping
Figure 2-2.2: Hydronic box piping diagram
Legend
1 Water side heat exchanger 9 Water pump
2 Water flow switch 10 Manometer
3 Refrigerant liquid line temperature sensor 11 Safety valve
4 Refrigerant gas line temperature sensor 12 Refrigerant gas side
5 Water outlet temperature sensor 13 Refrigerant liquid side
6 Water inlet temperature sensor 14 Water outlet
7
Air purge valve
15
Water inlet
8 Expansion vessel
Key components:
1. Air purge valve:
Automatically removes air from the water circuit.
2. Safety valve:
Prevents excessive water pressure by opening at 43.5 psi (3 bar) and discharging water from the water circuit.
3. Expansion vessel:
Balances water system pressure. (Expansion vessel volume: 8L.)
4. Water flow switch:
Detects water flow rate to protect compressor and water pump in the event of insufficient water flow.
5. Backup electric heater:
Provides additional heating capacity when the heating capacity of the heat pump is insufficient due to very low
outdoor temperature. Also protects the external water piping from freezing.
6. Manometer:
Provides water circuit pressure readout.
7. Water pump:
Circulates water in the water circuit.
1
2
3
45
6
7
8
10
11
12
13
15
9
14
F
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Part 2
-
Component Layout
and
Refrigerant Circuits
3 Refrigerant Flow Diagrams
Heating and domestic hot water operation
Figure 2-3.1: Refrigerant flow during heating or domestic hot water operation
Cooling and defrosting operation
Figure 2-3.2: Refrigerant flow during cooling and defrosting operations
Pressure sensor
Filter
Electronic expansion valve
Filter
High pressure
switch
Low pressure
switch
Air side heat exchanger
4-way
valve
High
tempera
tu
r
e, high p
r
essu
re g
as
High temperature, high pressure liquid
Low temperature, low pressure
Electronic expansion valve capiiiary
Hydronic box
Stop valve
Stop valve
Pressure sensor
Filter
Electronic expansion valve
Filter
High pressure
switch
Low pressure
switch
Air side heat exchanger
4-way
valve
High
tempera
tu
r
e, high p
r
essu
re g
as
High temperature, high pressure liquid
Low temperature, low pressure
Electronic expansion valve capacity
Stop valve
Stop valve
Hydronic box
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Service Manual
16 202004
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Part 3
-
Control
Part 3
Control
1 Stop Operation ........................................................................................ 18
2 Standby Control ....................................................................................... 18
3 Startup Control ........................................................................................ 19
4 Normal Operation Control ....................................................................... 22
5 Protection Control ................................................................................... 23
6 Special Control ......................................................................................... 26
7 Role of Temperature Sensors in Control Functions ................................... 29
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1 Stop Operation
The stop operation occurs for one of the following reasons:
1. Abnormal shutdown: in order to protect the compressors, if an abnormal state occurs the system makes a stop with
thermo off operation and an error code is displayed on the outdoor unit PCB digital displays and on the user interface.
2. The system stops when the set temperature has been reached.
2 Standby Control
2.1 Crankcase Heater Control
The crankcase heater is used to prevent refrigerant from mixing with compressor oil when the compressors are stopped.
The crankcase heater is controlled according to outdoor ambient temperature and the compressor on/off state. When the
outdoor ambient temperature is above 8°C or the compressor is running, the crankcase heater is off; when the outdoor
ambient temperature is at or below 8°C and either the compressor has been stopped for more than 3 hours or the unit has
just been powered-on (either manually or when the power has returned following a power outage), the crankcase heater
turns on.
2.2 Water Pump Control
When the outdoor unit is in standby, the internal and external circulator pumps run continuously.
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Part 3
-
Control
3 Startup Control
3.1 Compressor Startup Delay Control
In initial startup control and in restart control (except in oil return operation and defrosting operation), compressor startup
is delayed such that a minimum of the set re-start delay time has elapsed since the compressor stopped, in order to
prevent frequent compressor on/off and to equalize the pressure within the refrigerant system. The compressor re-start
delays for cooling and heating modes are set on the user interface. Refer to the M thermal Split Engineering Data Book
Part 3, 8.5 COOL MODE SETTING Menu and Part 3, 8.6 HEAT MODE SETTING Menu .
3.2 Compressor Startup Program
In initial startup control and in re-start control, compressor startup is controlled according to outdoor ambient
temperature. Compressor startup follows one of two startup programs until the target rotation speed is reached. Refer to
Figure 3-3.1, Figure 3-3.2.
Figure 3-3.1: MHA-V4(6)W/D2N8-B compressor startup program1 when ambient temperature is above 3°C
38rps
Target rotation speed
Compressor rotation speed (rps)
Time (s)
32rps 42rps 56rps
66rps 70rps
40s 60s 40s 40s 40s
120s
82rps
120s
Notes:
1. Once the first, 40-second stage of the program is complete, the program proceeds to the subsequent stages in a step-by-
step fashion and exits when the
target
rotation speed
has been reached
.
Figure 3-3.2: MHA-V4(6)W/D2N8-B compressor startup program1 when ambient temperature is at or below 3°C
38rps
Target rotation speed
Compressor rotation speed (rps)
Time (s)
0
32rps
42rps 56rps
66rps 70rps
40s
90s
60s 40s 40s
240s
82rps
240s
36rps
90s
Notes:
1. Once the first, 40-second stage of the program is complete, the program proceeds to the subsequent stages in a step-by-
step fashion and exits when the
target
rotation speed
has been reached.
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