How to choose the right type of air conditioner based on the outdoor space
I. Selection Strategies for HVAC Air Conditioner Types Based on Outdoor Space
The core judgment order is as follows: First, consider the size of the outdoor unit's installation location, ventilation, load-bearing capacity, noise level, and heat dissipation conditions → then match the model . Below are scenario-specific comparisons for easy application.
Key points: All air-cooled models ( multi-split units, cabinet units, rooftop units, air-cooled modules ) rely on outdoor ventilation for heat dissipation ; water-cooled/water-cooled units require cooling towers, and their space requirements and conditions are completely different.
II. The outdoor unit space is very small, and only one small outdoor unit can be placed (residential or small commercial storefront).
Suitable for: Split wall-mounted/cabinet air conditioners, home VRF multi-split air conditioners (one unit for multiple units)
Space requirements: Standard outdoor unit space with ventilation surface and sufficient space for maintenance and heat dissipation at the front and back (generally ≥10cm at the rear and ≥50cm at the exhaust side) .
Advantages: The outdoor unit is compact and the installation process is mature; multi-split systems have one outdoor unit that connects to multiple indoor units, reducing the number of outdoor units required .
Not suitable for: outdoor units that are close to the wall, enclosed by a balcony, or surrounded by high barriers (poor heat dissipation, prone to high-pressure protection at high temperatures, and poor cooling due to frequency reduction) .
Avoid these pitfalls: Placing the outdoor unit inside an enclosed balcony is preferred but not recommended; if you must place it there, you must install a forced ventilation duct, otherwise it is prone to malfunction in the summer .
III. Buildings with large rooftops/rooftop platforms (hotels, office buildings, shopping malls, factories)
Two mainstream solutions:
1. Rooftop air conditioning (rooftop RTU, direct expansion unit)
Suitable for: flat roofs with adequate load-bearing capacity, where the outdoor unit and air conditioning unit are integrated for direct air supply or connection to ductwork .
Space: The entire unit can be placed on the roof, with a centralized layout and short piping; the footprint of a single unit is smaller than that of an air-cooled module + water pump .
Features: Air-cooled direct expansion, no cooling tower required; suitable for single-story shops, supermarkets, factories, and small restaurants .
Disadvantages: Roof noise and sun exposure causing aging; proper roof waterproofing and drainage are required .
2. Air-cooled modular unit (water system main unit, paired with fan coil units/air handling units)
Suitable for: places with ample rooftop/ground platform space, where zoned control is desired, and where high comfort is required (hotels, office buildings, guesthouses) .
Space: Multiple modules should be placed side by side, and maintenance and heat dissipation channels (usually ≥1.2m) should be left between the units .
Features: Water system, quiet indoor environment, uniform temperature; can be started and stopped in batches, energy saving under partial load; can be expanded later .
Compared to VRF: the modular outdoor unit occupies a larger area and also needs to house a water pump and expansion tank; the piping is water pipe, not copper pipe .
3. Water-cooled screw/centrifugal chiller + cooling tower (for large complexes and large-area factories)
Suitable for: areas where cooling towers and chiller rooms can be placed on the roof or ground , with an area of several thousand square meters or more .
Occupancy: Cooling towers occupy a large area, require a well-ventilated and open location, and are prone to water spillage and noise; they also require a separate machine room .
Advantages: Highest energy efficiency under large-area operating conditions .
Disadvantages: The system is complex, requiring water treatment and regular maintenance; it is not cost-effective for small projects .
IV. There is ample open space on the ground, making it unsuitable for rooftop installations (industrial park facilities, low-rise factory buildings).
Priority: air-cooled modules and air-cooled screws , floor-mounted .
Note: Keep away from windows and living areas to prevent hot air backflow and noise pollution; the unit should not be placed in low-lying, waterlogged areas.
V. Outdoor units are located in scattered locations, with multiple small unit spaces (apartments, multi-story offices).
Preferred: VRF multi-split air conditioner (commercial multi-split air conditioner) with one outdoor unit per floor/area, or one outdoor unit spanning multiple floors with multiple indoor units .
Limitations: There are upper limits on the length and height difference of copper pipes; excessively long pipes will result in significant attenuation; ventilation must be ensured at all machine locations.
VI. There are almost no outdoor unit locations (renovation projects, interior rooms, no exterior walls).
Optional solutions:
Ductless air conditioners : still require an outdoor unit, but the indoor unit is hidden in the ceiling; cannot be selected if there is no available space .
Water source heat pump : There is groundwater/buried pipe (ground source heat pump), and there is almost no outdoor hot air unit, but the initial pipe laying takes up a huge amount of land .
Water-cooled units : Only if there is space for a cooling tower .
Not recommended: Portable air conditioner (exhaust hoses release hot air, resulting in poor performance and high humidity) .
Quick Comparison Summary
model | External space requirements | Typical scenarios | Key risk points |
Split wall-mounted air conditioner / floor-standing air conditioner | For small installation units, ventilation from one side is sufficient. | Family-run shops and small studios | Enclosed enclosure → High temperature protection |
VRF multi-split unit | Outdoor unit locations can be centralized or distributed. | Apartments, small to medium-sized offices | Copper tube ultra-long attenuation |
Air-cooled module (water chiller) | Roof/platform requires access for maintenance. | Hotels, guesthouses, office buildings | Large footprint, requires water pump |
RTU Roof Direct Expansion Unit | The roof is flat and has sufficient load-bearing capacity. | Supermarkets, single-story factories, stores | Roof waterproofing and sun protection |
Water-cooled chiller unit + cooling tower | Large open space for cooling towers and server rooms | Large buildings of tens of thousands of square meters | Floating water, water treatment, large footprint |
Ground source heat pump | Drilling wells and laying pipes on large tracts of land | Villas, residential complex | High initial land occupation and construction costs |
VII. Several methods for judging gold quality through on-site investigation
Hot air recirculation : Hot air from the outdoor unit's outlet should not blow onto itself or other outdoor units. If the wall/parapet wall is too high, it will trap hot air. You should choose a model that is one size larger or has a deflector .
Load-bearing capacity : When placing large units on the roof, it is essential to verify the roof load-bearing capacity. Many old roofs are not suitable for placing RTUs or modules .
Noise : If the outdoor unit faces the bedroom or window, prioritize water-cooled units ( fan coil units have no refrigerant noise indoors), or choose a low-noise type and build noise-reducing barriers .
Low temperatures in winter : For air-cooled units placed outdoors in northern regions, choose low-temperature models, electric auxiliary heating, and antifreeze; water-cooled units must be filled with antifreeze or drained .
Maintenance space : Don't just look at the size of the equipment itself. Maintenance access is a hard requirement . If you can't maintain it later, it's a waste of money.
