Midea M thermal A Mono Series User manual

M thermal A Series Mono(18~30kW)
Commercial Air Conditioners
R32
Service
Manual
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M thermal Mono
202008 1
CONTENTS
CONTENTS
Part 1 General Information ............................................................................ 3
Part 2 Component Layout and Refrigerant Circuits ..................................... 5
Part 3 Control ............................................................................................... 11
Part 4 Diagnosis and Troubleshooting ......................................................... 25
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Service Manual
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202008 3
Part 1
-
General Information
Part 1
General Information
1 Unit Capacities and External Appearance .............................................. 4
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1 Unit Capacities and External Appearance
1.1 Unit Capacities
Table 1-1.1: Capacity range
Capacity 18kW 22kW 26kW 30kW
Model MHC-V18W/D2RN8 MHC-V22W/D2RN8 MHC-V26W/D2RN8 MHC-V30W/D2RN8
1.2 External Appearance
Table 1-1.2: Appearance
18/22/26/30kW
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Part 2
-
Component Layout
and
Refrigerant Circuits
Part 2
Components Layout and
Refrigerant Circuits
1 Layout of Functional Components .............................................................. 6
2 Piping Diagrams ......................................................................................... 7
3 Refrigerant Flow Diagrams ......................................................................... 9
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1 Layout of Functional Components
Figure 2-1.1: MHC-V18(22,26,30)W/D2RN8 front view
Air side heat exchanger
Fan motor
Gas-liquid separator
DC inverter compressor
Electric control box
4-way valve
Pressure sensor
Electronic expansion valve
High pressure switch
Low pressure switch
Water pump
Safety valve
Manometer
Figure 2-1.2: MHC-V18(22,26,30)W/D2RN8 side view
Expansion vessel
Accumulator
One-way valve
Air purge valve
Water flow switch
Water side heat exchanger
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Part 2
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Component Layout
and
Refrigerant Circuits
LW
EW
1
4
14
6
9
26
19
8
8
20
25
2
5
7
11
12
17 18
21 22 23 24
3
15
13
27
16
F
10
2 Piping Diagrams
Figure 2-2.1: MHC-V18(22,26,30)W/D2RN8 piping diagram
Legend
1 Compressor 15 Low pressure switch
2 Discharge temperature sensor 16 Suction temperature sensor
3 High Pressure Switch 17 Single-way electromagnetic valve
4 4-Way Valve 18 Capillary
5 Outdoor temperature sensor 19 Water Inlet temp. sensor
6 Air side heat exchanger 20 Y-shape filter (Accessories)
7 Air side heat exchanger refrigerant outlet temperature sensor(cooling) 21 Water outlet temp. sensor
8 Filter 22 Manometer
9 Electronic expansion valve 23 Safety valve
10 Accumulator 24 Circulating pump
11 Refrigerant temperature sensor (liquid line) 25 Expansion vessel
12 Refrigerant temperature sensor (gas line) 26 Air purge valve
13 Pressure sensor 27 Flow switch
14 Gas-liquid separator
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Key components:
1. Accumulator:
Stores liquid refrigerant and oil to protect compressor from liquid hammering.
2. Electronic expansion valve (EXV):
Controls refrigerant flow and reduces refrigerant pressure.
3. 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.
4. 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.
5. Air purge valve:
Automatically removes air from the water circuit.
6. Safety valve:
Prevents excessive water pressure by opening at 43.5 psi (3 bar) and discharging water from the water circuit.
7. Expansion vessel:
Balances water system pressure. (Expansion vessel volume: 8L in 18/22/26/30kW units)
8. Water flow switch:
Detects water flow rate to protect compressor and water pump in the event of insufficient water flow.
9. Manometer:
Provides water circuit pressure readout.
10. Water pump:
Circulates water in the water circuit.
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Part 2
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Component Layout
and
Refrigerant Circuits
Pressure sensor
Filter
Electronic
expansion valve
Filter
High pressure
switch
Low pressure
switch
Air side heat exchanger
4-way
valve
High tempera
tu
re, high pressure g
as
High temperature, high pressure liquid
Low temperature, low pressure
Single-way electromagnetic valve Capillary
Accumulator
Pressure sensor
Filter
Electronic
expansion valve
Filter
High pressure
switch
Low pressure
switch
Air side heat exchanger Accumulator
4-way
valve
High tempera
tu
re, high pressure g
as
High temperature, high pressure liquid
Low temperature, low pressure
Single-way electromagnetic valve Capillary
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
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Service Manual
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Part 3
-
Control
Part 3
Control
1 Stop Operation ........................................................................................ 12
2 Standby Control ....................................................................................... 12
3 Startup Control ........................................................................................ 13
4 Normal Operation Control ....................................................................... 14
5 Protection Control ................................................................................... 16
6 Special Control ......................................................................................... 19
7 Roles of Temperature Sensors in Control Functions .................................. 22
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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 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 Mono Engineering Data Book
Part 3, 7.5 COOL MODE SETTING Menu and Part 3, 7.6 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. There are two startup programs which both have 60 second stage for compressor to startup. Once the 60
second stage 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.
3.3 Startup Control for Heating and Domestic Hot Water Operation
Table 3-3.1: Component control during startup in heating and domestic hot water modes
Component Wiring diagram label 18/22/26/30kW Control functions and states
Inverter compressor COMP
Compressor startup program selected according
to
ambient temperature and discharge temperature
DC fan motor FAN_UP / FAN_DOWN Fan runs at higher speed
Electronic expansion valve EEV1 304 steps
Four-way valve ST On
3.4 Startup Control for Cooling Operation
Table 3-3.2: Component control during startup in cooling mode
Component Wiring diagram label 18/22/26/30kW Control functions and states
Inverter compressor COMP
Compressor startup program selected according
to
ambient temperature and discharge temperature
DC fan motor FAN_UP / FAN_DOWN Fan runs at higher speed
Electronic expansion valve EEV1 304 steps
Four-way valve ST Off
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4 Normal Operation Control
4.1 Component Control during Normal Operation
Table 3-4.1: Component control during heating and domestic hot water operations
Component Wiring diagram label 18/22/26/30kW Control functions and states
Inverter compressor COMP
Controlled according to load
requirement from hydronic
system
DC fan motor FAN_UP / FAN_DOWN
Controlled according to
outdoor heat exchanger pipe
temperature, ambient temperature and compressor speed
Electronic expansion valve EEV1
Controlled according to discharge temperature,
discharge
superheat, suction superheat and compressor speed
Four-way valve ST On
Table 3-4.2: Component control during cooling operation
Component Wiring diagram label 18/22/26/30kW Control functions and states
Inverter compressor COMP
Controlled according to load
requirement from hydronic
system
DC fan motor FAN_UP / FAN_DOWN
Controlled according to
outdoor heat exchanger pipe
temperature, ambient temperature and compressor speed
Electronic expansion valve EEV1
Controlled according to
discharge temperature, discharge
superheat, suction superheat and compressor speed
Four-way valve ST Off
4.2 Compressor Output Control
The compressor rotation speed is controlled according to the load requirement. Before compressor startup, the M thermal
Mono outdoor unit determines the compressor target speed according to outdoor ambient temperature and discharge
temperature and then runs the appropriate compressor startup program. Refer to Part 3, 3.2 Compressor Startup
Program . Once the startup program is complete, the compressor runs at the target rotation speed.
During operation the compressor speed is controlled according to the setting and actual water temperature, the
refrigerant system pressure, refrigerant temperature and ambient temperature.
4.3 Compressor Speed Control
The running speed of six-pole compressors (used on all models) in rotations per second (rps) is one third of the frequency
(in Hz) of the electrical input to the compressor motor. The frequency of the electrical input to the compressor motors can
be altered at a rate of 1Hz per second.
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Part 3
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Control
4.4 Four-way Valve Control
The four-way valve is used to change the direction of refrigerant flow through the water side heat exchanger in order to
switch between cooling and heating/DHW operations. Refer to Figures 2-3.1 and 2-3.2 in Part 2, 3 Refrigerant Flow
Diagrams .
During heating and DHW operations, the four-way valve is on; during cooling and defrosting operations, the four-way
valve is off.
4.5 Electronic Expansion Valve Control
The position of the electronic expansion valve (EXV) is controlled in steps from 0 (fully closed) to 480 (fully open).
When the outdoor unit is power on:
The EXV first closes fully, then moves to the standby position (304 steps). After compressor runs for 60-second,
EXV is controlled according to ambient temperature. After a further 180s, EXV is controlled according to different
modes.
When the outdoor unit is in standby:
The EXV is at position 304 (steps).
When the outdoor unit stops:
The EXV is fully closed firstly, then moves to the standby position (304 steps).
4.6 Outdoor Fan Control
The speeds of the outdoor unit fans are adjusted in steps, as shown below.
Table 3-4.3: Fan speed index
Fan speed index Fan speed (rpm)
Upper fan Lower fan
W1 200 180
W2 280 260
W3 340 320
W4 400 380
W5 460 440
W6 520 500
W7 580 560
W8 640 620
W9 700 680
W10 760 740
W11 820 800
W12 880 860
W13 900 900
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4.7 Spray liquid cooling control
If the discharge temperature exceeds 105 , the solenoid valve opens. While the spray liquid cooling control is in progress,
the discharge temperature is judged every 20s and the frequency of compressor drops 2Hz until the minimum frequency
which differs from every model. When the discharge temperature is below 95 , the compressor runs at the current
frequency and solenoid valve closes.
If the discharge temperature exceeds 108 , the solenoid valve opens. While the spray liquid cooling control is in progress,
the discharge temperature is judged every 20s and the frequency of compressor drops 4Hz until the minimum frequency
which differs from every model. When the discharge temperature is below 95 , the compressor runs at the current
frequency and solenoid valve closes.
5 Protection Control
5.1 High Pressure Protection Control
This control protects the refrigerant system from abnormally high pressure and protects the compressor from transient
spikes in pressure.
Figure 3-5.1: High pressure protection control
Notes:
1. P
c
: Discharge pressure
When the discharge pressure rises above 4.2MPa the system displays P1 protection and the unit stops running. When the
discharge pressure drops below 3.2MPa, the compressor enters re-start control.
5.2 Low Pressure Protection Control
This control protects the refrigerant system from abnormally low pressure and protects the compressor from transient
drops in pressure.
Figure 3-5.2: Low pressure protection control
Notes:
1.
P
e
:
Suction
pressure
When the suction pressure drops below 0.14MPa the system displays P0 protection and the unit stops running. When the
suction pressure rises above 0.3MPa, the compressor enters re-start control.
Pc > 4.2MPa Pc < 3.2MPa
Normal operation
High pressure protection, error code P1 is displayed
Pe < 0.14MPa Pe > 0.30MPa
Normal operation
Low pressure protection, error code P0 is displayed
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Part 3
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Control
5.3 Discharge Temperature Protection Control
This control protects the compressor from abnormally high temperatures and transient spikes in temperature.
Figure 3-5.3: High discharge temperature protection control
When the discharge temperature rises above 115°C the system displays P4 protection and the unit stops running. When
the discharge temperature drops below 90°C, the compressor enters re-start control.
Figure 3-5.4:Low discharge temperature protection control
When the discharge temperature is lower than suction temperature for more than 5 minutes, the system displays EA
protection and the unit stops running. When the discharge temperature is higher than suction temperature, the
compressor enters re-start control.
5.4 Compressor Current Protection Control
This control protects the compressor from abnormally high currents.
Figure 3-5.5: Compressor current protection control
When the compressor current rises above Currentmax the system displays P3 protection and the unit stops running. When
the compressor current drops below Currentmax, the compressor enters re-start control.
Discharge temperature > 115°C Discharge temperature < 90°C
Normal operation
High discharge temperature protection, error code P4 is displayed
Tp Th for more than 5 minutes
Normal operation
Low discharge temperature protection, error code EA is displayed
Current > 28A Current < 28A
Normal operation
Compressor current protection, error code P3 is displayed
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5.5 Voltage Protection Control
This control protects the M thermal Mono from abnormally high or abnormally low voltages.
Figure 3-5.6: Compressor voltage protection control
When the phase voltage of AC power supply is at or above 265V for more than 30 seconds, the system displays H7
protection and the unit stops running. When the phase voltage drops below 265V for more than 30 seconds, the
refrigerant system restarts once the compressor re-start delay has elapsed. When the phase voltage is at or below 172V,
the system displays H7 protection and the unit stops running. When the AC voltage rises to at or more than 180V, the
refrigerant system restarts once the compressor re-start delay has elapsed.
5.6 DC Fan Motor Protection Control
This control protects the DC fan motors from strong winds and abnormal power supply. DC fan motor protection occurs
when any one of the following three sets of conditions are met:
Outdoor ambient temperature is at or above 4°C and actual fan speed differs from target fan speed by more than
200rpm for more than 3 minutes.
Outdoor ambient temperature is below 4°C and actual fan speed differs from target fan speed by more than 300rpm
for more than 3 minutes.
Actual fan speed is less than 150rpm for more than 20 seconds.
When DC fan motor protection control occurs the system displays the H6 error code and the unit stops running. After 3
minutes, the unit restarts automatically. When H6 protection occurs 10 times in 120 minutes, the HH error is displayed.
When an HH error occurs, a manual system restart is required before the system can resume operation.
5.7 Anti-freeze Protection Control
This control protects the water side heat exchanger from ice formation. The water side heat exchanger electric heater is
controlled according to outdoor ambient temperature, water side heat exchanger water inlet temperature and water side
heat exchanger water outlet temperature.
In cooling mode, if inlet water temperature or leaving water temperature or auxiliary heat source leaving water
temperature is below 4°C, the anti-freeze protection actions. In heating/DHW mode, if ambient temperature is below 3°C
and inlet water temperature or leaving water temperature or auxiliary heat source leaving water temperature is below 5°C,
the anti-freeze protection actions. In heating/DHW mode, leaving water temperature is below 2°C, the anti-freeze
protection actions. When water side heat exchanger anti-freeze protection occurs the system displays Pb and the unit
stops running.
Voltage 265V for 30s
or Voltage 172V
Voltage < 256V for 30s
or Voltage 180V
Normal operation
Compressor voltage protection, error code H7 is displayed
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Part 3
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Control
5.8 Module Temperature Protection Control
This control protects the module from abnormally high temperatures.
Figure 3-5.7: Module Temperature Protection Control
When the module temperature rises at or above 88°C, the system displays C7 protection and the unit stops running. When
the module temperature is below 81°C, error disappears and unit runs normally.
6 Special Control
6.1 Oil Return Operation
In order to prevent the compressor from running out of oil, the oil return operation is conducted to recover oil that has
flowed out of the compressor and into the refrigerant piping.
Timing of oil return operation:
When the compressor cumulative operating time with running rotation speed less than 42rps reaches 6 hours.
The oil return operation ceases when any one of the following three conditions occurs:
Oil return operation duration reaches 5 minutes.
Compressor stops.
Mode change command is received.
Table 3-6.1: Outdoor unit component control during oil return operation in cooling mode
Component Wiring diagram label 18/22/26/30kW Control functions and states
Inverter compressor COMP Runs at oil return operation rotation speed
DC fan motor FAN_UP / FAN_DOWN
Controlled according to outdoor heat exchanger pipe
temperature, ambient temperature, discharge
temperature and compressor speed
Electronic expansion valve EEV1 304 (steps)
Four-way valve ST Off
Table 3-6.2: Outdoor unit component control during oil return operation in heating and DHW modes
Component Wiring diagram label 18/22/26/30kW Control functions and states
Inverter compressor COMP Runs at oil return operation rotation speed
DC fan motor FAN_UP / FAN_DOWN
Controlled according to outdoor heat exchanger pipe
temperature, ambient temperature, discharge
temperature and compressor speed
Electronic expansion valve EEV1 304 (steps)
Four-way valve ST On
Module temperature 88°C Module temperature < 81°C
Normal operation
Module Temperature Protection, error code C7 is displayed
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