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Selecting the correct cable tray size is an important part of electrical system design. An undersized cable tray can lead to overcrowding, difficult cable installation, poor heat dissipation and limited future expansion. An oversized tray, on the other hand, may increase material, transportation and installation costs.
For commercial buildings, industrial facilities, data centers, solar power plants and infrastructure projects, cable tray sizing should be based on the actual cable requirements and the applicable electrical and installation standards.
In this guide, we explain how to calculate cable tray size step by step.
The required cable tray size depends on several factors:
Number of cables
Outside diameter of each cable
Cable type
Cable arrangement
Allowable cable fill
Required spare capacity
Cable weight
Tray depth
Support span
Installation environment
Future expansion requirements
The two basic dimensions that engineers normally consider are:
Cable Tray Width × Cable Tray Depth
For example:
300 mm × 100 mm Cable Tray
means the tray has a nominal width of 300 mm and a side height/depth of 100 mm.
However, selecting the correct tray size requires more than simply counting cables.
The first step is to prepare a cable schedule.
For each cable, determine:
Cable type
Quantity
Outside diameter
Approximate weight per meter
Voltage/application
Installation requirements
For example:
Cable Type | Quantity | Outside Diameter |
|---|---|---|
Power Cable | 10 | 25 mm |
Control Cable | 20 | 12 mm |
Communication Cable | 10 | 8 mm |
The outside diameter of the cable is important because cable tray width is primarily determined by the physical space required by the cables.
Always use the manufacturer's actual cable diameter when available instead of relying only on nominal cable size.
There are two common ways to approach cable tray sizing.
For cables arranged side by side, calculate the total cable width.
The basic formula is:
Required Cable Width = Sum of Cable Diameters
For example, if you have:
10 cables × 25 mm = 250 mm
20 cables × 12 mm = 240 mm
10 cables × 8 mm = 80 mm
The total cable width is:
250 + 240 + 80 = 570 mm
In practice, a 570 mm calculated width does not mean you should select a 570 mm tray.
Additional allowance is required for cable spacing, installation tolerance and future expansion.
Therefore, a 600 mm, 750 mm or other suitable standard tray width may be considered depending on the actual installation requirements and applicable standards.
Cable fill is one of the most important factors in cable tray sizing.
The tray should not be packed completely full. Adequate space is needed for:
Cable installation
Cable routing
Heat dissipation
Maintenance
Future cable additions
A simplified cable fill calculation can be expressed as:
Cable Fill (%) = Cable Occupied Area ÷ Available Tray Area × 100
For round cables, the approximate cross-sectional area of one cable can be calculated as:
Cable Area = π × D² ÷ 4
where:
D = outside diameter of the cable
For example, a cable with an outside diameter of 20 mm has an approximate cross-sectional area of:
π × 20² ÷ 4 ≈ 314 mm²
The total occupied area can then be estimated by multiplying the cable area by the number of cables.
However, the appropriate cable fill percentage depends on the applicable electrical code, cable type, tray type and installation method.
Always verify the final design against the applicable local code and project specification.
A cable tray should not be designed only for today's cables.
For many projects, additional cable capacity may be required in the future.
A common engineering approach is to include a spare capacity allowance, such as 20–30%, depending on the project specification.
For example:
Current required cable width:
500 mm
With 20% spare capacity:
500 × 1.20 = 600 mm
A standard 600 mm cable tray may therefore be considered, subject to the project's cable fill and installation requirements.
For large industrial projects, data centers and infrastructure projects, the required spare capacity may be specified by the owner or engineering consultant.
After calculating the required cable space and future allowance, select the next suitable standard tray width.
Common cable tray widths include:
100 mm
150 mm
200 mm
300 mm
450 mm
600 mm
750 mm
900 mm
1200 mm
The actual available sizes vary by manufacturer and project specification.
For example:
If the calculated requirement is approximately 520 mm, selecting a 600 mm tray may provide a practical solution.
If the requirement is approximately 680 mm, a 750 mm tray may be considered.
The final selection should also take into account cable arrangement, fill requirements, installation conditions and future expansion.
Cable tray depth is another important consideration.
Common tray depths include:
50 mm
75 mm
100 mm
150 mm
200 mm
300 mm
The required depth depends on:
Cable diameter
Number of cable layers
Cable arrangement
Cable weight
Required separation
Tray type
Project specifications
For a single layer of power cables, a relatively shallow tray may be sufficient.
For multiple cable layers or heavier cable systems, a deeper tray may be required.
Cable arrangement can significantly affect the required cable tray size.
Cables are arranged side by side.
This arrangement is often used for larger power cables because it can simplify installation and improve heat dissipation.
Cables are installed in multiple layers.
This may reduce the required tray width but increase the required tray depth and may affect cable fill and heat dissipation.
The appropriate arrangement depends on the cable type, electrical design, thermal requirements and applicable standards.
Cable tray sizing is not only about dimensions.
The selected tray must also be able to safely support the total cable load.
A simplified calculation is:
Cable Load (kg/m) = Sum of Cable Weight per Meter
For example:
10 cables × 2 kg/m = 20 kg/m
20 cables × 0.5 kg/m = 10 kg/m
Total cable weight:
30 kg/m
If future expansion is expected, additional load should also be considered.
The engineer should then compare the required load with the cable tray's rated Safe Working Load (SWL) at the specified support span.
For example:
Required Cable Load < Cable Tray SWL
However, the actual allowable load depends on:
Tray material
Tray thickness
Tray type
Tray width
Tray depth
Support spacing
Span length
Installation method
Applicable test standard
Cable tray load capacity is closely related to support spacing.
A tray tested at a short support span may have a different allowable load from the same tray installed at a longer span.
For example:
1.5 m support span
and
2.0 m support span
can produce different load-deflection performance.
Therefore, when selecting a cable tray, engineers should specify both:
Cable Tray Size + Support Span
rather than considering tray dimensions alone.
Cable tray size should also be selected together with the appropriate tray type.
Common cable management systems include:
Suitable for many commercial, industrial and infrastructure applications.
Provides a continuous bottom surface and can be suitable where additional cable protection is required.
Often used for large and heavy power cables because of its open structure and high ventilation.
Commonly used for data, telecommunications and smaller cables.
Provides an enclosed or partially enclosed cable management solution.
The tray type should be selected according to cable type, load, environment, installation method and project requirements.
The cable tray material and coating should match the installation environment.
Common options include:
Suitable for many indoor applications.
Provides enhanced corrosion protection and is widely used for outdoor and industrial environments.
Provides strong corrosion resistance and can be considered for outdoor installations and challenging environments.
Often selected for highly corrosive environments or applications with specific hygiene or corrosion requirements.
Provides an additional protective and decorative finish and is commonly used in indoor applications.
For solar projects, coastal areas and other outdoor environments, corrosion resistance should receive particular attention.
Let's consider a simplified example.
A project has:
10 power cables, 25 mm diameter
20 control cables, 12 mm diameter
10 communication cables, 8 mm diameter
10 × 25 = 250 mm
20 × 12 = 240 mm
10 × 8 = 80 mm
Total:
250 + 240 + 80 = 570 mm
Assuming 20% additional space:
570 × 1.20 = 684 mm
A standard 750 mm wide cable tray could therefore be considered.
However, this is only a simplified sizing example. The final cable tray selection should consider the actual cable arrangement, cable fill requirements, cable weight, support span, thermal requirements and applicable standards.
Before finalizing the cable tray size, check the following:
☑ Number of cables
☑ Cable outside diameter
☑ Cable arrangement
☑ Cable fill
☑ Future spare capacity
☑ Cable weight
☑ Tray load capacity / SWL
☑ Support span
☑ Tray width
☑ Tray depth
☑ Cable separation requirements
☑ Installation environment
☑ Corrosion resistance
☑ Material and surface finish
☑ Applicable standards
☑ Project specifications
Cable tray sizing is particularly important in grid-connected solar PV projects.
Solar installations may include:
DC cables
AC cables
Inverter cables
Transformer cables
Communication cables
Monitoring cables
Control cables
Cable trays may be installed outdoors on:
Rooftops
Solar carports
Ground-mounted PV systems
Inverter stations
Substations
Cable corridors
For outdoor solar projects, engineers should pay particular attention to:
UV exposure, corrosion, wind conditions, cable weight, support spacing, drainage and grounding/bonding requirements.
For projects located in coastal or high-humidity environments, the corrosion resistance of the cable tray system can be especially important.
Ten small cables and ten large power cables require very different tray sizes.
Always consider cable diameter and weight.
A completely full tray can make cable installation and maintenance difficult.
Always check the applicable cable fill requirements and project specifications.
A tray designed exactly for today's cables may become undersized after system expansion.
Consider appropriate spare capacity.
A cable tray's load capacity depends on the support configuration.
Always check the manufacturer's load data for the actual support span.
A cable tray installed indoors does not face the same conditions as one installed outdoors near the coast.
Select the appropriate material and surface treatment based on the project environment.
When requesting a cable tray quotation, providing the following information can help the manufacturer recommend the correct size:
1. Cable type and quantity
2. Cable outside diameter
3. Cable weight per meter
4. Required tray width
5. Required tray depth
6. Installation environment
7. Support span
8. Required material
9. Surface finish
10. Project country and applicable standards
For example:
Cable Tray: 600 × 100 mm
Material: HDG Steel
Cable Type: Power Cable
Support Span: 1.5 m
Application: Outdoor Solar PV Project
This information allows the manufacturer to recommend a suitable cable tray configuration and provide relevant technical data.
Correct cable tray sizing requires more than simply selecting a tray based on width.
The design should consider:
Cable quantity + cable diameter + cable arrangement + cable fill + spare capacity + cable weight + tray load capacity + support span + installation environment.
For large industrial, infrastructure, data center and solar PV projects, the final cable tray size should be verified against the applicable electrical standards and project specifications.
If you are unsure about the appropriate cable tray size, provide your cable list, cable diameter, cable quantity and support span to a qualified cable tray manufacturer. The manufacturer can then provide a suitable tray size, load data and technical recommendation.
Shenzhen Wanan Industrial Co., Ltd. is a China-based manufacturer of cable management systems and solar mounting solutions.
Our product range includes:
Perforated Cable Tray
Solid Bottom / Trough Cable Tray
Cable Ladder
Wire Mesh Cable Tray
Cable Trunking
Hot-Dip Galvanized Cable Tray
ZAM Cable Tray
Powder Coated Cable Tray
Solar Mounting Systems
Cable Conduit
We support OEM/ODM production, customized dimensions and international project requirements.
For cable tray sizing, product selection or technical requirements, contact our team with your cable schedule and project specifications.
Request a Cable Tray Catalog or Technical Datasheet →
Shenzhen Wanan Industrial Co.,Ltd.
MOB/Whatsapp:+86 18823394830
Email: admin@szwaindustry.com
Address：Wanan Industrial Park, Fengdong Village, Xinxu Town, Huicheng District, Huizhou，Guangdong
Whatsapp: +86-18823394830 
