The Cooper&Hunter CHML-U21RK3-NG is an inverter outdoor unit from the Nordic Multi Light R32 NG series, designed for multi-zone air-conditioning systems with 2–3 compatible indoor units.

With a nominal 6.10 kW cooling capacity and 6.50 kW heating capacity, the unit is suitable for larger apartments, private houses, offices and other multi-room spaces where several indoor units need to operate from a single outdoor unit. The system uses R32 refrigerant, supports a connected-capacity range of 50–150% of the outdoor unit’s rated capacity and is designed for cold-climate operation.

Key Features

Powerful Multi-Zone Cooling– With 6.10 kW cooling capacity, the CHML-U21RK3-NG is designed to provide comfortable cooling across several rooms using a single outdoor unit. The system supports 2–3 compatible indoor units, allowing each room or zone to have its own indoor unit and individual temperature settings. The manufacturer’s specified operating range of the connected indoor-unit capacity is 50–150% of the outdoor unit’s nominal capacity, providing flexibility when configuring different room sizes.

Efficient Heating– The unit delivers 6.50 kW nominal heating capacity and is designed for year-round operation. The detailed manufacturer specification gives a heating operating range of −22°C to +24°C. This makes the CHML-U21RK3-NG suitable for cold-weather operation and allows the multi-split system to be used as a supplementary heating solution during winter.

Stable Inverter Technology– The CHML-U21RK3-NG uses inverter compressor technology to continuously regulate output according to the actual demand of the connected indoor units.

Key advantages:

• Stable indoor temperature
• Efficient part-load operation
• Smooth compressor modulation
• Reduced unnecessary compressor cycling
• Lower mechanical stress
• Improved comfort

Stable Frequency Control allows smooth compressor operation at ultra-low frequencies down to 15 Hz.

 Noise Analysis Technology– The outdoor unit incorporates Noise Analysis Technology, developed to optimize system operation and reduce unnecessary operating noise. The manufacturer’s specified sound pressure level is approximately 58 dB(A).  Because this is a multi-split outdoor unit serving several indoor zones, installation should take into account the location of neighboring properties, balconies and bedrooms. Professional vibration isolation is recommended.

 R32 Refrigerant– The system uses modern R32 refrigerant. The manufacturer specifies a 1.60 kg factory refrigerant charge and an additional charge of 20 g/m when the installed pipe length requires it. The standard factory filling length is 30 m.

 Flexible Installation– The CHML-U21RK3-NG offers useful piping flexibility for residential and light commercial installations.

These limits should be strictly observed during installation to ensure correct refrigerant circulation and system performance.

Intelligent Defrosting– The Nordic Multi Light R32 NG series uses a new-generation Intelligent Preheating anti-icing system. Instead of relying only on a fixed time-based defrost cycle, the system initiates defrosting when it is actually required. This helps reduce unnecessary defrost cycles and associated energy losses during winter operation.

 Reliable Operation in Cold Weather

The CHML-U21RK3-NG incorporates several technologies intended to provide stable operation under demanding conditions:

• Stable Frequency Control
• Intelligent Preheating
• Automatic defrosting
• Anti-icing protection
• Multi-speed outdoor fan
• Auto Restart
• Self-Diagnosis
• Voltage protection
• Anti-corrosion protection
• Crankcase heating

The Nordic Multi Light R32 NG series also supports safe start-up within a 96–260 V voltage range.

Wide Operating Temperature Range– According to the detailed manufacturer specification:

Cooling: −15°C to +43°C
Heating: −22°C to +24°C

Cooper&Hunter additionally describes the Nordic Multi Light R32 NG platform as having a wide range of efficient operation from −20°C in heating to +48°C in cooling under the series’ specified conditions. For the individual product specification, however, the model-specific −15…+43°C / −22…+24°C figures are preferable.

Recommended Application– With 6.10 kW cooling and 6.50 kW heating capacity, this model can be considered for a total conditioned area of approximately 50–70 m², depending on the configuration of indoor units and building characteristics.

The actual required capacity should be calculated based on:

• Total floor area
• Individual room sizes
• Ceiling height
• Insulation quality
• Window area
• Solar exposure
• Number of occupants
• Internal heat sources
• Desired indoor temperature

Therefore, a fixed value such as 60–70 m² should be considered an approximate guideline rather than a guaranteed coverage area.

One Outdoor Unit — Up to Three Indoor Units– The CHML-U21RK3-NG is designed to connect 2–3 compatible indoor units.

This configuration can provide:

• Independent climate control in different rooms
• One outdoor unit instead of several
• Cleaner building facade
• Reduced external installation space
• Flexible zoning for bedrooms, living rooms and offices

Compatible indoor units must be selected according to Cooper&Hunter’s approved combination tables.

 Important Installation Information

The CHML-U21RK3-NG is an outdoor unit only and requires compatible indoor units to create a complete operating system.

Before purchasing, verify:

1. Compatibility of all selected indoor units.
2. Total connected indoor-unit capacity.
3. Maximum 60 m total refrigerant piping.
4. Maximum 20 m distance to an individual indoor unit.
5. Maximum 15 m height difference.
6. Required additional R32 refrigerant.
7. Electrical requirements.
8. Installation clearances and ventilation.

Professional HVAC installation is recommended.

Specification	Value
Model	CHML-U21RK3-NG
Series	Nordic Multi Light R32 NG
Type	Multi-Split Inverter Outdoor Unit
Compatible Indoor Units	2–3
Cooling Capacity	6.10 kW
Heating Capacity	6.50 kW
Connected Capacity Range	50–150% of rated outdoor-unit capacity
Energy Efficiency Class	A
Outdoor Airflow	3,800 m³/h
Outdoor Sound Pressure Level	58 dB(A)
Refrigerant	R32
Factory Refrigerant Charge	1.60 kg
Additional Refrigerant	20 g/m
Standard Pipe Length	30 m
Power Supply	220–240 V / 50 Hz / 1 Phase
Cooling Operating Range	−15°C to +43°C
Heating Operating Range	−22°C to +24°C
Maximum Total Pipe Length	60 m
Maximum Pipe Length to One Indoor Unit	20 m
Maximum Height Difference	15 m
Outdoor Unit Dimensions (W × D × H)	964 × 402 × 660 mm
Outdoor Unit Net Weight	47.5 kg
Outdoor Unit Gross Weight	52 kg
Liquid/Gas Pipe Connection	3 × 1/4″ / 3/8″
Mounting Point Distance	570 mm