A Guide to Avoiding Cable Selection Pitfalls: 5 Steps to Choosing the Right Cable and Avoiding Wasted Money

A Guide to Avoiding Cable Selection Pitfalls: 5 Steps to Choosing the Right Cable and Avoiding Wasted Money

In power engineering, construction, or equipment installation, cables are the "blood vessels" connecting energy to equipment. However, many projects frequently stumble upon cable selection pitfalls: either they use inferior cable for cheap, leading to overheating and fires; or they blindly pursue "large cross-sections and high configurations," resulting in material waste and skyrocketing costs. Ultimately, safety hazards often arise or budgets go over significantly.

In fact, scientific cable selection is not complicated. By mastering the following five key steps, you can accurately match your needs, ensuring safety while avoiding unnecessary costs.

Step 1: Define the Purpose - Ask "What is it for?"

Cables aren't just for power; different applications have vastly different performance requirements. Before selecting a cable, you must first understand its "mission."

For everyday electrical needs such as lighting, sockets, and air conditioning, conventional power cables such as YJV or VV are economical and practical.
However, for critical equipment like fire pumps, emergency lighting, and smoke exhaust fans, fire-resistant cables, such as the NH-YJV or WDZN series, must be used to ensure continuous circuit operation and the normal operation of rescue systems in the event of a fire.

Low-smoke, halogen-free cables should be prioritized in crowded places like subways, hospitals, and shopping malls. In the event of a fire, they can significantly reduce toxic smoke and buy valuable time for evacuation.

For low-voltage circuits such as control cabinets, instrument signals, and PLC systems, dedicated control cables, such as KVV or KVVP, should be used instead of power cables, as this can easily interfere with signals and cause malfunctions.

For applications where welding machines and mobile construction equipment are frequently dragged around, rubber-sheathed flexible cables should be selected for their flexibility, resistance to bending, and abrasion.

Remember: The application determines the type; mismatching can be detrimental.

Step 2: Calculate the load—current determines wire diameter.

The biggest concern with cables is "a small horse pulling a large cart." If the wire diameter is too small and the current carrying capacity is insufficient, prolonged operation will result in severe heat generation, accelerated insulation aging, and even fire. The core principle is: the safe current-carrying capacity of a cable must be greater than or equal to the maximum operating current of the equipment.
How to calculate?
First, check the power (kW) on the equipment nameplate, then calculate the current based on the voltage level. For a common 380V three-phase motor, you can estimate using the principle of "1 kW ≈ 2 amps." For example, a 15kW motor has an operating current of approximately 30A.
Next, consult the "Cable Current-Carrying Capacity Table" and select the smallest cross-sectional area that can carry that current. For a current of around 30A, 10mm² copper-core cable is generally sufficient.
However, for longer lines (over 80 meters), voltage drop must also be considered. Excessive voltage drop can cause equipment startup difficulties and malfunction. In this case, the wire diameter should be increased appropriately, such as to 16mm², to ensure stable voltage at the end.
Don't make a model selection based on experience or "approximately"; confirm it through calculation.
Step 3: Understand the Environment - Determine the Structure Based on the Laying Method
The cable's intended use determines the type of protective equipment it requires. If cables are laid openly in bridges or ducts, providing good heat dissipation, standard YJV or WDZ-YJY cables are generally sufficient, eliminating the need for additional armoring and saving costs.
If cables are laid through conduits, such as PVC or steel pipes, cables with smaller outer diameters and softer materials should be selected for ease of threading. Round-sheathed cables such as BV or RVV are suitable.
If cables are laid directly underground, steel-belt armored cables, such as YJV22, must be used. Underground environments are complex, subject to soil pressure, groundwater corrosion, and the potential for rodent bites and construction damage. The armor layer provides strong mechanical protection.
In humid and corrosive environments, such as chemical plants and pump rooms, models with corrosion-resistant sheaths should be selected. Stainless steel armor or low-smoke, halogen-free sheathing should be used if necessary to extend service life.
For equipment subject to frequent movement or vibration, such as cranes and welding machines, highly flexible rubber-sheathed flexible cables are essential; standard rigid cables are prone to breakage.
Different environments present different risks, and protective structures must be adjusted accordingly. Step 4: Identify Fake Labels - Don't Be Fooled by "Full Squareness"

Many low-priced cables on the market are "shrinking": nominally 10mm², but only 8mm² in actual measurement; cables claiming to meet national standards are actually non-standard or even "unauthorized standards."

These cables contain insufficient copper and have high resistance. Not only do they fail to meet current-carrying standards, they are also prone to overheating, a classic example of "saving money but buying hidden dangers."

How to Identify?

First: Weigh the cable. Copper is the primary cost of the cable. The lighter the weight of the same model, the more likely it is that corners have been cut. Ask the supplier for "kilometer weight" for comparison.

Second: Measure the wire diameter. Use a vernier caliper to measure the conductor diameter. For example, the standard diameter of a 4mm² copper conductor is approximately 2.25mm. If the actual measurement is less than 2.1mm, it can be considered "undersquared."

Third: Check the markings. Authentic cables will have the manufacturer's name, model, specification, implementation standard (such as GB/T 12706), and the 3C certification mark clearly printed on the outer sheath. Be extremely wary of products with blurry fonts or incomplete information.

Tip 4: Check the certifications. Confirm whether the product has passed the National Compulsory Certification (3C) certification. You can verify its authenticity through the official website of the China Quality Certification Center.

Don't be fooled by promises of "low price" and "guaranteed authenticity." Always rely on data.

Step 5: Comprehensive price comparison—calculate the total cost, not just the unit price.

When choosing cables, don't just focus on "price per meter"; consider the total cost over the entire lifecycle.

Using inferior cable, while saving a few dollars per meter, can lead to frequent failures, maintenance downtime, and even fire accidents, with losses far outweighing the material savings.

Conversely, over-specification is also undesirable. For example, a 5kW air conditioner might use 4mm² cable but opt ​​for 16mm². Not only does the cable cost more than double, but the costs for cable trays, conduit installation, and labor also increase, resulting in significant waste.

The truly smart approach is:

Select the most cost-effective solution while meeting safety regulations and technical requirements. Prioritize reputable manufacturers with reputable brands, complete test reports, and stable supply to avoid penny-wise and pound-foolish losses.

Evaluate price, quality, service, and long-term reliability comprehensively, rather than simply pursuing the lowest price.

Conclusion: Choosing the right cable safeguards both safety and efficiency.

Cable selection may seem trivial, but it actually impacts the safety of life and property. A precise selection ensures ten years of stable operation; a single compromise can lead to irreversible consequences.

Remember these five steps:

Clarify the intended use; determine wire diameter based on current;

Determine the structure based on the environment; identify fraudulent labeling;

Compare prices and consider the overall situation; and never compromise on safety.

Don't waste money, and don't take unnecessary risks—this is the embodiment of professionalism and responsibility.