Midea VC MAX Refrigeration System Introduction

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MBT 2023 VC MAX Series VRF Global Technical Trainings

22-30HP

8-20HP

Key Components

Essential Control

Refrigerant Circuit

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Refrigerant Circuit

8-12HP

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Refrigerant Circuit

14-20HP

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Refrigerant Circuit

22-24HP

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Refrigerant Circuit

26-30HP

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Compressor

Key Components

Essential Control

Refrigerant Circuit

Pressure sensor

Pressure switch

EEV

Solenoid valve

Oil separator

Accumulator

Microchannel heat exchanger

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Enhanced vapor injection (EVI) compressor

Compressor

SAVC060D11ULKA

SAVC070D44ULKA

SAVC096D33ULKA

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Anti-overcompression control technology

Dynamic scroll back pressure control technology

Differential pressure lubrication technology

Enhanced vapor injection technology*

High reliable bearing coating

High efficient concentrated stator

Ultra operation frequency range

Oil pool anti-turbulent technology

Dual-stage oil supply technology

Triple-stage oil and refrigerant filtration design

Optimized dynamic balance design

High efficiency neodymium magnet rotor

Compressor

*14-30HP unit’s unit has EVI function

MBT 2022 V8 Pro Series VRF Global Technical Trainings

Current limitation for compressors:

P32 &P33 Compressor Protection Control

This control protects compressors from abnormally high currents. It is performed for each compressor.

Compressor

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Compressor

Working principle

As the rotor rotates, the crankshaft drives the dynamic scroll in an eccentric rotary motion, compressing the low temperature, low pressure refrigerant and discharging high temperature, high pressure refrigerant from the center.

Refrigerant injection hole

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MBT 2023 VC MAX Series VRF Global Technical Trainings

M1. M2 or P.Q

Scenario: All IDUs in standby

1. When turn on the IDU, ODUs receive the IDU’s nominal load requirement.
2. ODUs correct load requirement according to ambient temperature.
3. Compressor starts up according to corrected load requirement, running frequency controlled by system pressure.
4. PI control starts when current discharge superheat reaches the target discharge superheat, or the initial running period finish.

Compressor frequency in startup

Frequency level

40

30

Initial control

PI control

Compressor

MBT 2022 V8 Pro Series VRF Global Technical Trainings

• In cooling mode, it can improve super-cooling degree, the super-cooled refrigerant can achieve better performance for indoor units.

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• Refrigerant volume in microchannel heat exchanger is controlled according to temperature difference between its inlet(T6A) and outlet(T6B) or the temperature difference between discharge temperature and target discharge temperature.

Microchannel heat exchanger

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Measurement method

• In standby, measure resistance between sensor terminals
• Between black line (black pin) and red line (red pin) the resistance should be about 98MΩ; after reversing the pins, the resistance should be same

Pressure sensor

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MBT 2023 VC MAX Series VRF Global Technical Trainings

• Sensor resistance increases as the system discharge pressure increases. So test pressure sensor in standby.
• V_dd = 5V
• Formula: V_out = 0.8696 * P + 0.5 Range: 0.5 – 4.67 VDC (0 – 4.8MPa)

Pressure sensor

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MBT 2023 VC MAX Series VRF Global Technical Trainings

P12 High Pressure Protection Control

This control protects the system from abnormally high pressure and protects the compressors from transient spikes in pressure.

Controlled by high pressure sensor.

Pc ≥4.15MPa

Pc<3.5MPa

Normal operation

High pressure protection, error code P12

P22 Low Pressure Protection Control

This control protects the system from abnormally low pressure and protects the compressors from transient drops in pressure.

Controlled by low pressure sensor.

Pe<0.07MPa for 60s

Pe≥0.15MPa

Normal operation

Low pressure protection, error code P22

Pressure Protection

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Structure

Pressure switch

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Initial state

Work state

Protection state

Pressure increase

Working principle

Pressure switch

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Structure

Expansion valve

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MBT 2023 VC MAX Series VRF Global Technical Trainings

• Positions: 0 (fully closed) to 480 /3000(fully open)
• Controlled by pulse signal (12VDC)

Expansion valve

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Coil resistance measurement

• Outdoor unit’s EEV has 5 wire, normally, white wire is the common terminal
• Resistance between common terminal and other terminals: 46±4 Ω @20°C

Valve Jammed

• After indoor unit power on, if coil is working but valve is not active, lightly knock EEV body with a rubber hammer or screw driver several times, to see if it can be recovered.

Common terminal

Expansion valve

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Structure

Solenoid valve

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MBT 2023 VC MAX Series VRF Global Technical Trainings

• Ensure the valve body avoid high temperature during brazing
• Ensure no impurities enter valve body during installation or repair
• Connect copper pipes according to direction marked on valve body (side inlet and bottom outlet)
• Abnormal supply voltage causes abnormal valve open or close(200V AC is required to open the solenoid valve)

Solenoid valve

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Solenoid valve SV6:

• Allows refrigerant to bypass the expansion valve
• Controlled according to discharge temperature in cooling mode
• The SV6 is only available for 26-30HP

Solenoid valve SV5:

• Controls the refrigerant from microchannel heat exchanger to gas-liquid separator.
• Cooling mode: it will be on all the time
• The SV5 is only available for 14-30HP

Solenoid valve

Solenoid valve SV8:

• Allows refrigerant injection
• Open when compressor start and close when compressor stop
• SV8A/SV8B are only available for 26-30HP

SV8 close

SV8 open

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Oil separator

Structure

• Shell, steel ball, filter, guide vane, oil return pipe

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Oil separator

Work principle

• The mixture of the refrigerant and oil, which comes from the compressor, will enter the oil separator from inlet pipe. The mixture will flow a guide vane. The mixture will hit to shell and flow spirally, The oil will be separated due to centrifugal force and fall down along the shell to the bottom. The refrigerant gas will go to outlet pipe and enter the condenser with a oil less status.
• Oil will return to compressor from suction pipe.
• Separation efficiency is up to 99%

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Accumulator

Structure

• Shell, inlet and outlet refrigerant pipes, oil orifice
• Separates liquid refrigerant from gas refrigerant, stores liquid refrigerant and oil to protect compressor from liquid hammering.

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Crankcase heater control

Key Components

Essential Control

Refrigerant Circuit

Fan speed control

Oil return

Overload control

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MBT 2023 VC MAX Series VRF Global Technical Trainings

• The speed of the outdoor fan is adjusted in steps, the motor has up to 40 steps.
• During unit start up, the initial fan speed is limited according to static pressure mode.
• The limitation speed of the ODU models as below table.

Initial control： The initial step is 0, and then the initial speed is run according to the outdoor side temperature. If ambient temperature is high in cooling mode, the initial speed is high.

Initial control

PI control

Pl control：According to the target high pressure control, gear change value △Q= K1 (pressure change rate )+K2 (pressure change value) * period T

Fan speed control

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Oil return

• In order to prevent compressors from running out of oil, the oil return operation is conducted to recover oil that has flowed out of the compressor(s) to the piping system.
• This operation is performed for all units including units that are in standby.
• When the outdoor unit is running in oil return, the digital display on outdoor main PCB will display “d0”.
• Timing of oil return operation: when the initial cumulative operating time reaches 2 hours and then every 8 hours

IDU component control in Cooling mode:

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Oil return

Outdoor unit component control in cooling:

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MBT 2023 VC MAX Series VRF Global Technical Trainings

Normal operation

Overload control is used to maintain comfort requirement (i.e. outlet air temperature) and keep proper system pressure

Overload control, indoor units operates in low fan speed

More than 130% need to be customized, up to 200%

Overload control

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MBT 2023 VC MAX Series VRF Global Technical Trainings

THANK YOU

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MBT 2023 VC MAX Series VRF Global Technical Trainings