When M&E contractors are tasked with delivering dependable, cost-effective cooling and heating for small to medium-sized commercial spaces, Mitsubishi Electric’s PU and PUZ P-Series outdoor units are often the perfect fit. Designed for light-commercial projects, these systems provide the balance between advanced inverter technology and straightforward single-zone operation.
This detailed guide will help you understand the full product range, technical specifications, compatible indoor units, installation best practice, common commissioning issues, and real-world applications — all based on manufacturer data and practical installer experience.
Explore our commercial air conditioning installation services:
https://www.climateworks.co.uk/commercial-air-conditioning
PU vs PUZ: Understanding the Difference
- PU: Cooling-only outdoor units. Best for applications where heating is not required — for example, server rooms, laboratories, or temperature-sensitive retail environments.
- PUZ: Heat pump models capable of heating and cooling, ideal for offices, classrooms, clinics, and other multi-season applications.
Both ranges are engineered for quiet, reliable operation and are built to withstand challenging site conditions. They can be paired with a wide selection of Mr Slim P-Series indoor units, making them versatile for different building layouts and client needs.
Full Model Range and Specifications
Below is a summary of the main PU/PUZ commercial outdoor units based on Mitsubishi Electric's official technical literature.
PU Models (Cooling Only):
- PU-A12NKA7
- PU-A18NKA7
- PU-A24NKA7
- PU-A30NKA7
- PU-A36NKA7
- PU-A42NKA7
PUZ Models (Heat Pump):
- PUZ-A12NKA7
- PUZ-A18NKA7
- PUZ-A24NKA7
- PUZ-A30NKA7
- PUZ-A36NKA7
- PUZ-A42NKA7
Technical Highlights
From the P-Series product guide and datasheets:
- Capacity Range:
- Cooling: 3.6 kW to 12.3 kW
- Heating: 4.0 kW to 14.0 kW (PUZ models only)
- EER/COP Values:
- Cooling EER up to 3.33
- Heating COP up to 3.77
- Operating Range:
- Cooling down to −5°C (up to −20°C with wind baffle)
- Heating down to −15°C for standard models, −20°C for Hyper Heating variants
- Refrigerant: R410A, pre-charged for up to 30 metres (model dependent)
- Piping Limits:
- Max length: 30–50 m depending on model
- Max height difference: 30 m
- Sound Levels:
- 44–52 dBA (cooling)
- 46–53 dBA (heating)
- Dimensions and Weight:
- Heights range from 880 mm to 1,330 mm
- Weights from 60 kg to 110 kg
Compatible Indoor Units
PU/PUZ outdoor units are compatible with a range of Mr Slim P-Series indoor models:
- PKA: Wall-mounted units for smaller offices and meeting rooms
- PLA: 4-way ceiling cassette units for open-plan areas
- PCA: Ceiling-suspended units for kitchens, gyms, and workshops
- PEAD / PEA: Low and mid-static ducted units for discreet installations
- PVA: Multi-position air handlers for flexible applications
This compatibility allows installers to tailor solutions to each client’s needs without over-specifying.
Installation Best Practice
- Location Planning: Always choose a site with adequate airflow and clearance — at least 1000 mm at the discharge side, 300 mm on the intake sides.
- Pipe Runs: Ensure total length and height difference remain within limits to avoid compressor strain. Charge with additional refrigerant where runs exceed the pre-charged length.
- Electrical Connection: Confirm correct phase and voltage (198–253 V). Use appropriately sized cabling based on model current draw.
- Low Ambient Operation: Install wind baffles where cooling is required below −5°C. Without baffles, coil frosting and shutdowns may occur.
- Mounting: Use anti-vibration mounts to minimise structure-borne noise in offices or residential-adjacent sites.
- Drainage: Ensure condensate drains are correctly graded and terminated.
Accessories and Options
- Wind Baffle Kits: For extended low-ambient cooling
- Vane Controls: For optimising airflow direction indoors
- Drain Pumps: For units installed below indoor condensate exit level
- PAR Controllers: Wall-mounted wired controllers with advanced scheduling
- Wireless Remote Options: For retrofit scenarios without wall wiring
Commissioning Q&A and Fault Handling
Q: Outdoor unit does not start
- Confirm control signal from indoor unit
- Check M-N signal wiring for continuity and polarity
- Inspect fuses and circuit breakers
Q: Unit runs but delivers no cooling
- Check refrigerant charge and system pressures
- Ensure indoor filters are clean and fans are operational
- Inspect for kinked pipework or valve closure
Q: Low heating output in cold weather
- For PUZ models, confirm defrost cycle operation
- Check coil cleanliness and fan speed settings
- Verify Hyper Heating model selection for sub-zero climates
Q: Fault Code P8 – Compressor Overload
- Inspect airflow over coils
- Check refrigerant charge
- Measure compressor winding resistance
Q: Fault Code U4 – Communication Error
- Verify M-N wiring continuity
- Inspect for swapped polarity at either end
- Reset system and retest
Example Project Applications
Office Fit-Out in Guildford
- PUZ-A30NKA7 heat pump paired with two PLA cassettes and one PEAD ducted unit
- Outdoor unit roof-mounted with wind baffle for −10°C operation
- Commissioned with weekly setback schedules for energy savings
Healthcare Clinic in Basingstoke
- PUZ-A18NKA7 heat pump paired with wall-mounted PKA units
- Focus on low noise and air cleanliness
- Condensate drains connected to dedicated hygienic discharge
Retail Store in Wokingham
- PU-A36NKA7 cooling-only outdoor with ceiling-suspended PCA units in open shop floor
- Optimised for summer cooling with minimal structural changes
When to Specify PU/PUZ P-Series over VRF
- Projects requiring a simple single-zone system
- Sites with limited ceiling space and no need for extensive ductwork
- Lower capital expenditure compared to VRF
- Faster installation for time-critical fit-outs
Related Pages
References
- Mitsubishi Electric P-Series Product Catalogue 2024
- Mitsubishi Electric PUZ-A and PU-A Series Service Manuals
- Mitsubishi Electric Low Ambient Cooling Guides
- Building Regulations Part F – Ventilation
- IET Wiring Regulations, 18th Edition
Dr. Julian Carter
Dr. Julian Carter is a highly experienced thermal systems expert with over 15 years in the field, holding a PhD in thermal systems. His career spans academic research, consulting, and teaching, focusing on air conditioning and refrigeration systems. Dr. Carter bridges the gap between theoretical advancements and practical applications, providing expert insights to organisations like ClimateWorks, where his guidance informs decision-making and industry best practices. Notably, he has worked on international projects with organisations such as Daikin Industries, the International Institute of Refrigeration (IIR), and the United Nations Environment Programme (UNEP). These collaborations addressed energy performance, sustainable refrigerants, and advanced cooling technologies. Currently a lecturer at Edinburgh University, Dr. Carter combines his expertise with a passion for educating the next generation of engineers and advancing climate control technologies.
Get a fast no obligation quote today
.png){kind=small}
