Cable Installation Specifications for Diesel Generators

The power of a diesel generator is proportional to the cable used: the higher the generator power, the larger the required cable size. Conversely, using an undersized cable poses safety risks. The selection of cables for diesel generators is directly linked to the generator’s current—cables must safely carry the generator’s maximum current.

A critical step in diesel generator installation is cable wiring. Improper cable installation can significantly impact subsequent operation. Below are key specifications:

Conduits

1.Select conduits in compliance with local regulations.

2.Surface-mounted conduits must be properly supported and secured.

3.Conduit systems must be grounded.

4.Install the conduit system before pulling cables through.

5.Conduits must have at least 40% free space.

6.The inner bend radius of elbows must be no less than 2.5 times the conduit’s outer diameter.

7.Conduit systems should prevent dust and water ingress, with ventilation openings required at the highest and lowest points.

8.Openly routed conduits must be made of fire-resistant materials.

Cable Trays

1.Steel cable trays must conform to specified standards.

2.Ensure adequate bending radius during installation.

3.Like steel conduits, steel trays are compliant with wiring regulations for conductor protection but do not provide fire resistance.

4.Cable trays must have at least 45% free space.

5.Trays require proper supports and fixing points.

6.Tray covers should not be placed on the underside; when passing through walls, floors, or ceilings, covers must fit tightly.

7.Vertically mounted trays must contain heat-resistant materials to prevent excessive temperature buildup in upper sections.

Circuit Isolation

Different circuit cables must be isolated to prevent electrical and physical contact. Standards define three circuit categories:

1.Low-voltage circuits powered by the main power supply (excluding fire alarm or emergency lighting circuits).

2.Extra-low voltage or communication circuits powered by safety power supplies (e.g., telephone, address, and data transmission systems).

3.Fire alarm or emergency lighting circuits.

Cable Ladders

1.The most common method is to lay cables on perforated cable ladders.

2.Cables should be arranged flat with a maximum fastening spacing of 450 mm.

3.Typical support spacing for cable ladders is 1200 mm.

4.Ladders must have sufficient strength, with a load capacity exceeding the total cable weight by at least 25% to accommodate future expansion.

Cable Trenches

1.Cable trenches in generator rooms and equipment rooms must be enclosed with concrete or checker plate covers.

2.Trenches should be constructed to minimize the bending radius of the largest cables.

3.Trenches should be as straight as possible with smooth surfaces and a slope to drain water and oil into a sump.

Underground Installation

1.Armored shielded cables can be directly buried with a 75 mm thick bedding layer.

2.The spacing between high-voltage and low-voltage cables in trenches or direct burial should be 160–400 mm.

3.When routed under roads, walkways, or structures, cables must be protected by ducts or guards to prevent mechanical damage.

4.Reserve space for future cable installations.

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