Air conditioning trunking is used to cover pipework, cables and condensate drainage between an indoor air conditioning unit and the outdoor condenser.
It is one of the simplest ways to make a split air conditioning installation look cleaner and more professional, particularly where the pipework runs along an external wall.
However, trunking comes in different sizes. Choosing the right size depends on the pipework, insulation, electrical cables, condensate drainage and how many services need to fit inside the trunking.
In this guide, we explain how air conditioning trunking works, what size you may need, the difference between 72mm, 80mm and 100mm options, and what to consider before ordering.
You can also browse our air conditioning installation accessories or read our Air Conditioning Installation Accessories Buyer’s Guide.
What Is Air Conditioning Trunking?
Air conditioning trunking is a protective cover installed over the services running between different parts of an air conditioning system.
For a typical split system, this can include:
- Refrigeration pipework
- Pipe insulation
- Electrical cable
- Control cable
- Condensate drainage
Instead of leaving these exposed on an external or internal wall, trunking encloses them within a neat channel.
This helps protect the services while also creating a much cleaner finished appearance.
Why Use Trunking For Air Conditioning?
Trunking is not simply decorative. It can play an important role in protecting an installation.
Benefits include:
- Hiding exposed pipework
- Protecting insulation and cables
- Creating a neater finish
- Keeping several services together
- Making external pipe routes less noticeable
- Helping protect pipework from weather and accidental damage
- Giving installers a structured route around walls and corners
For domestic installations in particular, trunking can make a significant difference to how the finished installation looks.
What Size Air Conditioning Trunking Do I Need?
The correct trunking size depends on how much needs to fit inside it.
The main factors are:
- Refrigeration pipe diameter
- Thickness of pipe insulation
- Number of pipes
- Electrical cables
- Condensate pipe or hose
- Number of bends in the route
- Whether extra space is needed for easier installation
As a general principle, it is better to have a little spare room than to force pipework tightly into trunking that is too small.
Your installer should be able to confirm the correct trunking size for the system being fitted.
72mm, 80mm Or 100mm Trunking?
CoolEasy offers several trunking sizes, including 72mm, 80mm and 100mm options.
| Trunking Size | Typical Use | Best For |
|---|---|---|
| 72mm | Compact service runs | Smaller pipework routes where space inside the trunking is limited |
| 80mm | General air conditioning installations | Many standard domestic and light commercial split system installations |
| 100mm | Larger service runs | Larger pipework, more cables or installations needing additional internal space |
This is only a general guide. The exact size needed depends on the air conditioning system and installation.
When Might 72mm Trunking Be Suitable?
72mm trunking is a relatively compact option.
It may work well where the pipework and cables do not require a large amount of internal space.
It can be useful where:
- The pipework is relatively small
- The route only contains a limited number of services
- A slimmer appearance is preferred
- The installer has confirmed the services will fit comfortably
The key point is not to choose a smaller trunking simply because it looks less noticeable. The pipework still needs enough room to sit correctly inside.
Browse our black 72mm air conditioning trunking.
When Might 80mm Trunking Be Suitable?
80mm trunking can provide a useful balance between appearance and internal capacity.
It may suit many standard domestic and light commercial installations where the pipework, cables and drainage need to be enclosed together.
It may be suitable for:
- Wall mounted split air conditioning systems
- Typical domestic installations
- External wall pipe routes
- Installations where pipework and drainage share the same route
Again, the required size will depend on the exact system being fitted.
Browse our white 80mm air conditioning trunking.
When Might 100mm Trunking Be Better?
100mm trunking provides more internal space.
This can be useful for larger air conditioning systems, larger insulated pipes or installations where several services need to run together.
You may consider larger trunking where:
- The refrigeration pipes are larger
- Thicker insulation is used
- There are additional electrical cables
- Condensate drainage runs through the same trunking
- The pipe route contains several bends
- The installer wants more room to position services correctly
Larger trunking may be more visible, but it can produce a cleaner result than trying to squeeze too many services into a smaller channel.
Browse our black 100mm air conditioning trunking.
Do Different Air Conditioning Systems Need Different Trunking Sizes?
Yes. Different air conditioning systems can use different pipe sizes and installation layouts.
A small wall mounted split system may have relatively compact pipework, while a more powerful commercial system may require larger pipes.
Trunking requirements can also change depending on:
- System capacity
- Manufacturer specification
- Single split or multi split installation
- Number of indoor units
- Distance between indoor and outdoor units
- Condensate drainage route
- Electrical cable requirements
Always choose the pipework first according to the system specification, then choose trunking that comfortably accommodates the completed service run.
What Goes Inside Air Conditioning Trunking?
A typical trunking run may contain several different services.
Refrigeration Pipework
The refrigeration pipes connect the indoor and outdoor units and allow refrigerant to circulate through the system.
Pipe Insulation
The refrigeration pipework is normally insulated, which means its finished diameter is larger than the copper pipe itself.
Electrical Cable
Depending on the system, electrical or communication cables may follow the same route.
Condensate Drainage
The condensate pipe removes water produced by the indoor unit during operation.
All of this needs to be considered when deciding how much room is required.
Remember The Pipe Insulation
One common mistake is looking only at the diameter of the copper pipe.
Air conditioning refrigeration pipework is insulated, so the finished pipe can take up substantially more space than the bare copper itself.
For this reason, consider:
- The size of both refrigeration pipes
- The insulation thickness
- How the pipes will sit next to each other
- Any drainage or cable running alongside them
If everything only just fits before installation, the trunking may be too small once bends and fittings are added.
Do You Need Space For Condensate Drainage?
Often, yes.
The condensate drain from the indoor unit may follow the same route as the refrigeration pipework.
This means trunking may need enough room for:
- Two insulated refrigeration pipes
- Electrical cable
- Condensate pipe or hose
The drainage route is particularly important because condensate needs to flow correctly.
If gravity drainage is not possible, the installation may require a condensate pump.
Browse our condensate removal products.
White Vs Black Air Conditioning Trunking
Trunking colour is mainly an appearance decision.
White trunking works particularly well with:
- White render
- Light coloured walls
- White window frames
- Most standard white indoor air conditioning units
Black trunking may suit:
- Dark cladding
- Black window frames
- Dark brickwork
- Modern extensions
- Properties with black external detailing
If the pipe route will be particularly visible, choosing a colour that complements the building can make the installation considerably more discreet.
Why Trunking Fittings Matter
A trunking system usually includes more than straight lengths.
Depending on the pipe route, the installer may also need:
- Internal corners
- External corners
- Flat bends
- Wall covers
- End pieces
- Connectors
- Joint covers
These fittings allow the trunking to follow the building cleanly rather than leaving awkward gaps or exposed services.
When planning a run, think about the complete route rather than simply measuring the total length of straight trunking.
Plan The Pipe Route Before Ordering
Planning the route first helps avoid ordering the wrong amount of trunking or missing important fittings.
Before ordering, identify:
- Where the indoor unit will sit
- Where the services will exit the wall
- Where the outdoor unit will sit
- The total distance between them
- How many corners are required
- Whether the route travels vertically or horizontally
- Where the condensate will drain
- Any obstacles such as windows, doors or pipework
A straightforward route usually creates a cleaner installation and can also reduce the amount of trunking required.
How Much Air Conditioning Trunking Do I Need?
Measure the complete service route from the point where the pipework becomes visible to the outdoor unit.
Do not simply measure the straight line between the indoor and outdoor units.
Allow for:
- Vertical drops
- Horizontal runs
- Corners
- Offsets
- Outdoor unit connection points
- A small amount of contingency
Your installer can usually confirm the required quantity before installation.
Can Trunking Be Used Indoors?
Yes. Air conditioning trunking can also be used inside a property where pipework cannot pass directly through the wall behind the indoor unit.
This may happen when:
- The indoor unit is fitted on an internal wall
- The pipework needs to travel across part of the room
- The most practical wall exit is some distance from the unit
- The building layout prevents a direct external route
For internal installations, appearance can be particularly important, so planning the shortest and neatest route is worthwhile.
Can You Paint Air Conditioning Trunking?
Some customers may want trunking to blend more closely with the wall.
Whether a particular trunking product can be painted will depend on its material and manufacturer guidance.
If appearance is important, choosing a suitable trunking colour from the start is usually the simpler option.
Trunking For Multi Split Air Conditioning
Multi split air conditioning systems can require more installation planning because several indoor units connect to the outdoor system.
This can mean:
- More pipework
- Several separate pipe routes
- Larger combined service runs
- More junctions and corners
- More condensate drainage
Depending on the layout, larger trunking or several individual trunking routes may be required.
For multi split systems, it is particularly useful to plan the complete installation before ordering accessories.
Trunking For Domestic Air Conditioning
For homes, trunking often plays an important aesthetic role.
A neat external route can help a wall mounted air conditioning installation blend into the property rather than leaving visible insulated pipework running down the wall.
When planning domestic trunking, consider:
- Wall colour
- Window and door positions
- Drainage route
- Outdoor unit position
- Visibility from gardens or neighbouring properties
- How many corners will be needed
If the appearance of the finished installation matters, discuss the trunking route with the installer before work begins.
Trunking For Commercial Air Conditioning
Commercial installations may have longer or more complicated service runs.
In offices, shops, restaurants and other commercial buildings, trunking can help protect and organise exposed services while keeping the installation tidy.
Commercial installations may require:
- Larger trunking
- Longer runs
- More fittings
- Multiple indoor unit routes
- Additional electrical cabling
- More complex drainage arrangements
The system specification and installation plan should determine the trunking requirement.
Common Air Conditioning Trunking Mistakes
Avoid these common mistakes when choosing trunking:
- Choosing trunking before confirming the pipe size
- Forgetting the thickness of pipe insulation
- Forgetting condensate drainage
- Choosing the smallest size purely for appearance
- Not leaving enough room around bends
- Measuring only the straight line between the units
- Forgetting corner pieces and connectors
- Ordering the wrong colour
- Not planning the complete route before installation
- Trying to force too many services into one trunking run
Air Conditioning Trunking Buying Checklist
Before ordering, check:
- Which air conditioning system is being installed?
- What pipe sizes does the system require?
- How thick is the pipe insulation?
- Will electrical cables run inside the trunking?
- Will the condensate drain run inside it?
- What size trunking has the installer recommended?
- How long is the complete pipe route?
- How many corners are needed?
- Are connectors or wall covers required?
- Would white or black trunking suit the property best?
- Is enough trunking being ordered to allow for the complete route?
CoolEasy Air Conditioning Trunking
White 80mm Air Conditioning Trunking
Our white 80mm air conditioning trunking is a versatile option for installations where a clean white finish suits the property.
Black 72mm Air Conditioning Trunking
Our black 72mm air conditioning trunking provides a slimmer dark finish for suitable pipework routes.
Black 100mm Air Conditioning Trunking
Our black 100mm air conditioning trunking provides more internal room where larger pipework or additional services need to be enclosed.
Air Conditioning Trunking FAQs
What is air conditioning trunking used for?
Air conditioning trunking covers and protects refrigeration pipework, cables and condensate drainage between different parts of an air conditioning installation.
What size air conditioning trunking do I need?
The right size depends on the refrigeration pipes, insulation, electrical cables and drainage that need to fit inside. Your installer should confirm the appropriate size.
Is 80mm trunking suitable for air conditioning?
80mm trunking can suit many standard air conditioning installations, but the correct size depends on the specific pipework and services being installed.
When would I use 100mm trunking?
100mm trunking can be useful when larger pipework, thicker insulation or additional cables and drainage require more internal space.
Can condensate pipe go inside air conditioning trunking?
Yes. Condensate drainage often follows the same route as the refrigeration pipework, provided the trunking is large enough and the drainage can be installed correctly.
Should air conditioning pipework always be covered?
Not necessarily, but trunking helps protect exposed services and creates a much neater finished installation.
Can air conditioning trunking be used outdoors?
Suitable air conditioning trunking is commonly used externally to protect and conceal service runs. Always use products intended for the installation environment.
Should I choose black or white trunking?
Choose the colour that best suits the property. White works well with light surfaces, while black can blend better with dark brickwork, cladding or window frames.
Do I need fittings as well as straight trunking?
Usually, yes. Corners, bends, connectors and wall covers may be needed depending on the route between the indoor and outdoor units.
Who should install air conditioning trunking?
Trunking is normally fitted as part of the wider air conditioning installation. Fixed split systems should be installed by appropriately qualified professionals where required.
Final Advice: Choose Trunking After Planning The Pipe Route
The best trunking size is the one that comfortably fits all the services required for the air conditioning system.
Do not choose purely by appearance. Pipe size, insulation, drainage, cabling and the number of bends all affect how much space is needed.
For many installations, 72mm, 80mm or 100mm trunking can provide a clean way to cover the service route, with white and black options available to suit different properties.
Plan the route first, confirm the pipework requirements with your installer, then choose trunking with enough internal space for a neat installation.
Browse our installation accessories, compare our air conditioning trunking options, or speak to the CoolEasy team if you need help choosing the right accessories for your installation.