It’s not just the product – it’s also how you use it.
There are many right and wrong ways to wire an industrial control panel according to NEC (National Electric Code) standards. Sure, the specs of the wire itself matter (and we’ll cover them below), but layout and safety planning are arguably even more important.
Stick these eight guidelines as virtual Post-It notes in your mind whenever you begin a high-stakes control panel wiring project:
Cable and wire are an underappreciated step in executing a great industrial control panel design. To help your final product run safely and smoothly, follow best practices for:
NFPA 79, a standard produced by National Fire Protection Association, outlines wiring regulations for industrial control panels that operate at 600 V or less. Part of its purpose is to help you select the right wire size.
AWG (American wire gauge) is a measurement of diameter that clues buyers in to the expected performance of a given wire. Using cable components with the proper insulation thickness for your application results in a just-right amount of voltage and a more efficient panel.
Excessive current flow can damage components, while a lack of voltage can limit device effectiveness. In general, the more electrical juice you need, the thicker cable insulation you’ll want to keep heat radiation from causing a short-circuit or fire.
Remember that electrical panels must manage multiple voltage levels, and you’ll need different wire gauges for each.
There’s good and bad to a connection having more wire than it needs at the moment (hint, hint).
The bad first: Excessive wire length can cause:
Keep wire lengths reasonable, but not so short that they cause problems for the operator later.
The good side of slack: It can save you a huge hassle when expanding or rearranging the control cabinet after installation. This is why we’re also pro-service loops – having an extra few inches is infinitely more convenient than having to find and label a new wire.
(Pro tip: Store wire slack under the main wireway and away from devices.)
Don’t forget that the supporting trays and ducts need to fit the job too!
Using the right cable trays and ducts helps keep the cabinet organized, reducing the chance of damage from neighboring components.
Fortunately, NFPA 79 helps out again by providing specs for wire trays and conduits. When planning to run wires, consider both “how much” and “how big.” Then size your ducts, conduits, and other raceways to match.
The physical build of an industrial wire falls under one of two categories: stranded or solid.
A solid wire has a single, solid core. A stranded wire is actually a twisted-up bundle of several thinner wires.
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Stranded Wire |
Solid Wire |
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Affordability |
✅ |
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Current Capacity |
✅ |
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Current Distance |
✅ |
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Flexibility |
✅ |
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Durability |
✅ |
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Maintenance |
✅ |
Overall, when in doubt, lean toward stranded wire (but ask an expert first).
This wire type generates less heat, and its conductors can withstand up to millions of flex cycles. If a thread of stranded wire breaks, you can get away with repairing only the broken strand. If part of a solid wire breaks, the whole thing goes in the scrap heap.
A disclaimer on current capacity: Although stranded wire has less resistance overall, each strand is more resistant than an identical-size solid wire. Using stranded wire may lead to disappointing results in high-current applications.
Cable jacketing and wire insulation material determine the wire’s self-preservation abilities. Many industrial-grade wire materials need to be extremely durable to withstand their environments.
Depending on application, the top design factors in choosing a wire material may be:
NEC’s Article 409 (Section 104, to be exact) is all about wire spacing. And for good reason – it’s probably the aspect of panel design that engineers botch the most.
Many spacing catastrophes start with the control panel’s surface area being too small to begin with. Right away, the assembly can’t meet wiring space and bending space requirements.
It’s incredibly easy to avoid these violations with a little foresight:
Follow these tips, and you’ll be known as the hero who extended your panel assembly’s life span.
With all the expensive and intricate devices you need to accommodate in a control panel layout, it’s easy to prioritize the wiring last. But those fancy parts will perform better if you give equal attention to the supporting cast.
One way to start? Grabbing a CAD tool that optimizes routes for you. While you’ll need to check the software’s work and tweak as needed, using CAD ultimately saves material cost and install time.
Your goal is to make a clean, logical, and protected layout:
Other practices to keep in mind:
Failing to wire certain components in a certain way will spell certain doom.
Safety circuits protect a panels’ control and power devices. These protective elements include fusible switches, circuit breakers, and relays.
For example, safety relays detect wire breaks (among other faults) by sending an electrical pulse through the wiring. The relay measures the flow of current, detecting any interruptions. Also, most electronic safety circuits keep the machine from operating if the circuit is open.
An interesting and nuanced concept in safety circuits is wiring them in series. This strategy can keep wire layout simple, effective, and low-cost.
Wiring safety components in series means that if any section isn’t properly closed, the entire circuit will open, stopping the machine. Safety circuit controls can require series wiring so that the panel remains safe if a connection suddenly loosens or breaks.
There’s one drawback to weigh: Series-wired circuits with 5+ safety switches, or those with heavy-use switches or gates, don’t perform quite as well. They also carry a higher risk of fault masking, which means fixing one switch or fault may deceive the technician into missing a second issue. If this sounds like too much trouble for your particular application, consult with a panel expert about a more sophisticated solution.
Secure and well-insulated connections are key to reliable control panel performance. Loose terminations can cause safety hazards and voltage drops.
A good termination process begins with using a connection method appropriate for the application. It should end with covering the connection with a terminal block or heat-shrink tubing so there’s no accidental contact.
Some additional best practices for panel wire termination:
Poor electrical grounding is one of the top causes of control panel failure. It’s a human safety risk and produces electrical noise that hampers device performance.
Route your grounding wires separately from power cables. This prevents the current from cross-mingling among wires and becoming a shock risk.
There are other ways your control device layout design can promote safe, effective grounding:
Grounding best practices can vary based on your industry’s electrical panel and wiring standards, codes, or other requirements. If you’re outsourcing the panels’ manufacturing, your contracted panel engineering company may be able to help with compliance.
Sometimes, the single action of trying to locate a wire inside a panel can translate to long production outages. Think about how much 1 hour of downtime could cost you or the end buyer.
And you don’t need us to tell you the safety risk of labeling wires poorly or not at all.
Whether you prefer wraps, flags, or direct labels, the basic rules are the same. All control panels should have clear and visible labels, identifying each component’s function and its wiring points. They should be durable enough to remain readable through years of use in the panel’s environment.
Other points to consider when labeling industrial wires:
Proper panel wire management is crucial for control device operation and maintenance that’s safe, yet efficient.
Commit best practices to memory, whether your control panel production happens in-house or elsewhere. Even today, some panel manufacturing happens in small, local shops that specialize in instrumentation, but lack understanding of NEC requirements.
To learn more about the right and wrong of control panels, from insulation thickness to design-for-serviceability, visit our resource center: