11 Questions to Ask Before Selecting a Multi-Conductor Cable

11 Questions to Ask Before Selecting a Multi-Conductor Cable

11 Questions to Ask Before Selecting a Multi-Conductor Cable

When it’s time to make an investment that will impact long-term business continuity, uptime, and effectiveness, you want to make sure you get it right. There’s little room for error or guesswork.

Like with many important product purchases, when it comes to purchasing multi-conductor cables, the trick is to find the right balance between cost and performance.

By learning as much as you can about these cables before you make a purchasing decision, you’ll avoid the hassle of discovering too late (likely during installation) that the solution you chose wasn’t the best option after all. This discovery can lead to rework and overspending, as well as system failure and unplanned downtime.

Not all multi-conductor cables are created equal. The decisions you make shouldn’t be based solely on price – your application and environment need to be considered, too. They’ll help you determine the type of cable construction and material you need for the results you want.

But First, What’s a Multi-Conductor Cable?

From small electronic components to factory automation applications, multi-conductor cables can be found all over. They safely transmit signals and electrical power over one cable to control applications.

To do this, multi-conductor cables bring several insulated conductors together inside a jacket. You may hear the term “multipair cable” as well, which refers to a type of multi-conductor cable designed to guard against electromagnetic interference and crosstalk by twisting insulated conductors into pairs before they’re placed inside a jacket.

Multi-Pair vs Standard Multi-Conductor

You’ll find multi-conductor cables in:

  • Food and beverage manufacturing facilities, connecting things like machinery, robots, assembly lines, conveyor systems, and control systems
  • Factories and mills, connecting equipment like furnaces, lighting, and thermal elements
  • Machine tool manufacturing, supporting cranes and hoists, as well as conveyor and transport systems
  • Automotive plants, used for processing equipment and tray wiring
  • HVAC applications, controlling things like motor speeds and on/off settings for VFDs, pumps, and compressors

Because they’re used in so many applications – serving as control cables, VFD cables, robotics cables, and much more – multi-conductor cables are one of the most common types of cable around. They play a critical role in our daily connected communications.

Picking the Right Multi-Conductor Cable - Which Questions to Ask

How can you pinpoint the right multi-conductor cable for your application? First, consider your environment. Then, select a multi-conductor cable constructed for that setting. The four components that make up these cables – conductors, insulation, shielding, and jacketing – directly impact whether a cable will work in your plant or facility.

Before you make a purchasing decision, ask yourself these questions about your environment. Your answers will guide you to the right choice.

1. Are extremely high temperatures present in your plant?

If high heat is a regular occurrence, then pay special attention to cable insulation and jacket materials.

In factories or mills – or even in applications where baking equipment, lighting, or heating elements are located nearby – high temperatures may impact cable performance.

To avoid overheating, melting, or other issues, select a multi-conductor cable with insulation and a jacket designed to withstand high-heat environments. Cable materials like TPE (thermoplastic elastomer) and silicone can protect against high temperatures, ensuring long life and protecting against damage from heat.

Industrial Oven

Always reference the cable’s maximum rated temperature (which is based largely on its materials of construction) and consider potential “over-temperature” conditions in your application.  Also be aware that many cable designs will have more than one “maximum temperature” depending upon the application, for example a PVC-insulated multi-conductor cable could be rated to 221°F (105°C) in stationary use, but only to 194°F (90°C) for flexible, motion-based applications.

2. Are chemicals, oils, lubricants, or machinery coolant present in your plant?

If so, then pay special attention to the cable’s jacketing. The right material will protect your cable from harsh liquids and chemicals.

Just because chemicals, oils, lubrication, and/or machinery coolant are common in factories and food and beverage environments doesn’t mean all multi-conductor cables are designed to withstand them. Their presence should factor into your cable selection.

To maintain flexibility, multi-conductor cables contain plasticizers inside their insulating compounds. If these plasticizers come into contact with harsh chemicals, oils, or lubrications through absorption, cable degradation, performance failure, and potential downtime can occur. Once this happens, it can’t be undone.

A few examples of possible damage from exposure to chemicals or oils include:

  • Swelling, which increases cable diameter
  • Softening or melting, which leads to loss of cable flexibility and elongation
  • Discoloration, which can eventually lead to cracking
  • Hardening or cracking, which also leads to loss of cable flexibility and elongation

Cable Swelling due to Oil

Swelling

Cabled Melted due to Oil

Melting

Discolored Cable due to Oil

Discoloring

Cable Cracking Due to Oil

Cracking

In these environments, it’s important to select a cable with a jacket designed to withstand these liquids, such as one made of polyurethane (PUR). It resists oils and chemicals better than other jacketing materials, including the commonly used polyvinyl chloride, or PVC (although PVC also has the ability to resist oil and acid in certain environments). 

3. What types of surfaces are present near the cable?

Will it be installed across or near a rough surface? Will something rub up against it? If so, your cable needs a jacket that can withstand this abrasion.

In environments where abrasion exists, cables can fail when their jackets are too thin or soft to protect shielding and conductors inside. Look for heavy-duty PUR cable jackets, which resist cutting or wearing away from rubbing against rough surfaces. It will take a very high number of strokes to cause the cable’s insulation to fail if it’s jacketed in the right material.

Cable Broke Due to Abrasion

4. Is moisture or humidity a possibility in your plant?

If cables will be used in wet environments – or in locations with high humidity – then corrosion may be a concern. Selecting the right conductor material can improve performance in these conditions.

Bare copper conductors are suitable in most of today’s industrial sites and are suitable for use in ultrasonic welding applications, but tinned copper (covered in metal alloy) is better suited for wet, high-humidity applications and are very easy to solder. Both offer similar performance, but tinned copper conductors will last longer in production and process environments.

5. Is fire a possibility in your environment?

If so, then you’ll need a cable jacket with a low smoke zero halogen (LSZH) classification. This type of thermoset jacket is suitable for installation in places where fire possibilities exist.

Although fires can start nearly anywhere, some environmental conditions are favorable for potential fires: dust accumulation, flammable liquids and gases, welding or other hot work, overloaded electrical wiring, or even friction inside heavy machinery. Depending on the application and the applicable standards (UL in the United States, CSA in Canada, IEC in Europe, etc.), there are several levels of flame resistance. 

In general, the strictest type of flame resistance is for plenum rated cable, followed by riser-rated cable.  Both of these apply to critical applications where human beings work or reside such as permanent installation within buildings and dwellings. (see next question).  Other common industrial types of flame ratings include FT4 and FT1 (CSA Vertical Tray Tests) and UL VW-1 (UL1581 Vertical Flame Test)

Airplane Cable Installation

Lastly, low smoke zero halogen (LSZH) cables utilize jacketing materials that are safer when exposed to fire; they don’t produce as much dense smoke or highly toxic gases like non-LSZH cables, such as those with PVC jackets. If a cable with an LSZH classification encounters fire, fewer toxic fumes and less smoke will be emitted as it melts, keeping people and equipment safer.

6. Where will the cables be installed?

Are cables going into air-return (plenum) spaces? Below raised floors? If the installation involves a plenum or underfloor space, then the cable should be rated for that environment.

By selecting a cable rated for plenum spaces, you can rest easy knowing that the jacket and insulation materials allow safe operation with smoke and low-flame characteristics. Featuring high heat ratings and fire resistance, they can support technology such as signaling, sensors, security systems, HVAC equipment, and communications systems.

Cable Installed in Plenum Area

 

7. Is electrical noise present in your environment (and how much)?

Every environment experiences some amount of electrical noise (RFI or EMI), whether it’s from motors, lighting systems, wireless devices, two-way radios, or other cables. Very small amounts of interference are manageable, but noisy environments need shielded cables.

A shielded cable eliminates unwanted circuit noise through a metallic layer that prevents EMI and RFI from entering or emitting from the conductor. Without shielding, electrical noise may impact the cable’s performance, create crosstalk (interference), or impact the performance of equipment and electronics.

The type of cable shielding you select should be based on the type of electrical noise being generated in your environment. For example:

  • Foil shielding is ideal for environments with high-frequency interference
  • Braided shielding works best in environments with low- or medium-frequency interference
  • Spiral shielding should be used only in environments with low-frequency interference
  • Braided/foil shielding combines the benefits of both, making it very effective in extremely noisy environments (such as utility plants or heavy industrial sites)
OLFLEX SERVO Cable with Shielding

 

In certain applications, multipair cable – a specific type of multi-conductor cable – can also be used to defend against noise. Their construction (insulated conductors twisted into pairs before being placed inside a jacket) is effective at preventing noise, crosstalk, and interference.

8. Is movement and automation (robots, cobots, conveying systems, etc.) present in your environment?

If your plant utilizes moving technology, then cable flexibility is crucial. Flexibility is impacted by all four components of the cable: the conductor, insulation, shield, and jacket.

Flexibility can literally make or break the ability for a cable to be used in a certain situation. Many of today’s industrial environments call for cables that offer flexibility and a small bend radius to accommodate tight clearances, maximize space usage, and route around equipment or machinery. Forcing non-flexible cables into applications where tight bends or routing are required can generate crosstalk, interference, or cable damage.

If cables will be used in a fixed application (lay static a straight line), then flexibility isn’t usually necessary. A cable with a solid conductor will fit the bill (solid conductors tend to be stiff and inflexible). Remember, some flexibility may be necessary for routing, so make sure to take that into consideration.

Robotic Arm

If your application involves automation or movement (robots, moving gantries, etc.), however, then flexible cables will be needed to withstand bend. Look for cables with stranded conductors (multiple smaller strands grouped together) vs. one solid conductor.

Multi-conductor cables are available with different strand counts (the higher the strand count, the more flexible the cable). Determine upfront how much installation room is available – as well as what the cables will need to be installed around – and you’ll be able to accommodate the flexibility and bend radius requirements you need.

If you’re utilizing a shielded cable to control noise interference, some shield types are more flexible than others. While braid shields offer some flexibility, foil shields are even more flexible – but their ability to “flex” doesn’t last as long.

Insulation and jacketing material also impact flexibility, with some compounds having more than others. Silicone, for example, offers high levels of flexibility.

9. Will cable glands be used to secure your cable and provide strain relief?

If cable glands will be used, then insulation and jacket materials matter to keep diameters as small and round as possible. If cable glands won’t be used, then the thickness or roundness of the cable may not be as important.

If a cable gland (cord grip) will be used to prevent accidental pullout, decrease potential stress or damage, relieve strain, or create a tight seal to prevent dust or moisture intrusion, then cable diameter – and the ability to maintain roundness and a consistent diameter (no swelling) – matters.

For example, cables with pressure-extruded jackets maintain roundness with a consistent diameter that eliminates convolutions. As a result, they create a better seal when used with cable glands or cord grips.

Cable Gland Installed

10. How important is the installation speed for your project?

Are you in a hurry to get multi-conductor cables installed? Is there a deadline that needs to be met? If so, certain cable choices can be easier to handle and install than others.

If your project isn’t a rush job, then maybe speed isn’t a huge concern. But, if you’re on a tight timeline or have limited labor available, choosing the right multi-conductor cable can reduce installation time.

Consider tube extrusion cables, for example. They feature a tube jacket that’s faster and easier to strip as opposed to a pressure-extruded jacket. If you use automated cutting/stripping wire processing machines, this option can make the installation process go faster.

11. Are space constraints a factor (congested cable trays, narrow conduit, etc.)?

If you’re installing in tight spaces or small cable trays, then jacket and insulation thickness and weight can matter.

Based on the cable you select, its overall diameter (thickness) can make it more difficult to install in congested cable trays or narrow conduit. If space is at a premium in your installation environment, select a cable with minimal jacket thickness and smaller cable diameter. This will allow you to run more cable through your trays or conduit.

In other applications such as vehicles, moving industrial equipment and other use-cases the overall weight of a cable can matter.  Different material formulations can factor into the overall weight per foot of the multi-conductor cable.

Cables with a novel jacket and insulation materials such as mPPE can reduce overall cable diameter by up to 50% while reducing weight up to 65% versus industry-standard PVC materials.

PVC vs mPPE Jackets

Learn More About Multi-Conductor Cables

Want to learn more about choosing the right multi-conductor cable for your environment and finding the right balance between price and performance? Contact Lapp Tannehill and we'll be happy to help you find the right cable for your needs. Reach us at 800.633.6339 or chat with us online.

Browse Multi-Conductor Cables

Now that you know what to consider when selecting a multi-conductor cable, take a look through the multi-conductor cables that Lapp Tannehill offers. As a distributor, we have access to a variety of manufacturers to help you find what you need.

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