Take a walk around your home or office, and you’ll likely see many items with clearly printed expiration dates. From adhesives and fire extinguishers to batteries, paint, and smoke detectors, everything has its useful limit.
But are the same sentiments true about products like electrical wire – does it expire?
Electrical wire doesn’t so much “expire” as it degrades over time.
Its lifespan depends on many factors, including the environment, installation, potential threats, and maintenance. Wire exposed to heat, moisture, sunlight, or corrosive substances is less safe than properly stored or installed material.
Knowing your wire anatomy goes a long way toward understanding how it may eventually degrade.
If you look at a typical piece of electrical wire, it’s got two main components:
Conductor: Usually copper or aluminum, it moves electrical current
Insulation: Made from materials like PVC, XLPE, or rubber, it protects the conductor from damage
While the conductors themselves don’t expire, the insulation surrounding them deteriorates over time, leading to brittleness and cracks. Those cracks can eventually expose conductors to the elements, leading to safety risks like arcs, sparks, and short circuits.
With that said, it’s possible to improve a wire’s usable lifespan. Environmental conditions matter, but so do wire type, voltage, and even how you store and install it.
When people consider a product’s usable life, they usually focus on how long it will last after installation. While that’s one part of the equation, the other involves how long a product sits on the shelf.
But what’s the difference between the two, and how do they impact each other?
Shelf Life: How long can wire sit on the shelf or in storage and still perform as expected? This metric is used to describe wires before installation.
Service Life: How long does a wire function once it’s in use and current is running through it? This helps explain how long wires will last after installation.
High-quality electrical wire has a shelf life of 10 to 20 years when stored inside a cool, dry place. Once installed, it largely depends on voltage, temperature, and environmental stress.
Wire can work for decades in the right environment, but you must properly maintain it.
If the current exceeds the wire’s rating, it can overheat, causing fires. Warmer ambient temperatures can also cause the wire insulation to potentially degrade faster. Use appropriately rated wire for the conditions.
Different metals can react differently in the same environment. Copper wire, for example, doesn’t rust and is a durable conductor. However, it can corrode if the conductor is subjected to moisture.
Aluminum wiring is a less expensive option compared to copper, but it’s less conductive. It also expands more when heated, which could result in loose connections. Additionally, aluminum is more likely to oxidize than copper, resulting in reduced performance and increased resistance.
Like conductors, insulation composition matters. For example, any conductors insulated with cloth are way past their service life and could pose a fire risk. Newer insulations like PVC, HDPE, and XLPE protect conductors and dissipate heat and noise more efficiently.
High temperatures or moisture can accelerate insulation degradation, especially in poorly ventilated spaces. In some climates, this can happen in just a few years. Fluctuating temperatures can cause similar damage, shortening life expectancy.
The problem is that higher operating temperatures cause wire resistance to increase. The additional heat generated by the resistance can melt insulation, exposing conductors and creating fire risks.
Moisture and humidity are different in that they increase conductivity. When water makes contact with a live conductor, it can lead to arcs, sparks, and faults.
This comes down to wear and tear – frequently used wire degrades faster. The same is true for wire exposed to higher electrical loads.
By reducing use and lowering loads, electrical conductors could last longer.
The world is a dangerous place, and even the strongest wire insulation may struggle in certain situations.
UV light exposure can break down insulation stored outdoors or in direct sunlight. After a period of time, it becomes brittle and more likely to crack.
Conductors aren’t impervious to damage from bending, crushing, and improper coiling, and could have internal damage. Some insulations are more resilient than others, making them better for situations where crushing and abrasions are a threat.
Wires stored near harsh chemicals, oils, or in corrosive environments can suffer from insulation breakdown or metal corrosion.
Some installs are harder than others. Twists, turns, and bends, especially in tight areas, can stress or damage wire insulation or conductors.
Outside, rocky soil, humidity, heat, sunlight, and chemical exposure may occur, impacting wiring systems.
Though the environment can lead to shorter wire service lives, poor installation can have a similar result. Packing too many wires in the conduit, dragging it over rocks, exceeding bend radius, loose connections, and poor placement can all take a toll.
Rodents can cause incredible damage by chewing through insulation and exposing conductors.
Even if a wire is physically intact, it may no longer meet National Electrical Code or NFPA ratings.
The key to getting the longest service life possible for your wire comes down to getting the little things right.
Before installing wire, prepare it for use. For example, in cold environments, allow the wire a day or two to warm up in a dry location before installing it. The heat helps the wire bend more easily and prevents the insulation from becoming brittle.
During installation, avoid kinks, hard bends, and twisting. These actions can damage the insulation, potentially exposing conductors.
Know the voltage and operating temperatures BEFORE the installation begins. Then choose a wire gauge large enough to safely perform in those conditions. Accidentally overloading the circuit can cause excess heat and resistance, leading to failure.
The last thing any installer wants to do is ruin wire during the electrical installation process.
Workers should avoid overfilling conduits, forcing wire around tight corners, or applying too much tension. Also, try to avoid locations where something might snag, scratch, crush, or cut the wire.
The best way to prevent a dangerous situation is to avoid one in the first place.
Regularly inspect wires for fraying, cracking, or other damage, and install traps if you notice rodent nests or droppings. Workers can also check for hot spots along the wire, which indicate potential damage.
Flickering lights, odd smells, and discolored electrical outlets aren’t minor inconveniences; they’re warning signs. Take them seriously and address them early on by examining the electrical system.
Knowing when to replace electrical wiring often comes down to noticing when something isn’t quite right.
Common examples of when it might be time to change wiring include:
Sometimes, the wire’s composition alone makes it a candidate for replacement. For example, old knob-and-tube or cloth-wrapped wiring isn’t up to code and well past its service life. Additionally, ungrounded outlets and constantly tripping circuit breakers are clues that the electrical system needs an update.
When in doubt, it’s safer to discard the old wire and use a fresh, certified product that meets all current NEC guidelines.
Although electrical wire doesn’t have a specified expiration date stamped on it, time, exposure, and environment matter.
When it comes to electrical safety, it’s always better to be safe than sorry. If you’re dealing with old wire or reusing materials, carefully inspect them for damage. When in doubt, contact a licensed electrician, your local Codes Department, or review the NEC guidelines.
Wire and cable can last for decades under the right conditions. It comes down to choosing the best product for the job and conditions and performing consistent maintenance.
With the situation under control, you’re well on your way toward maximizing your wire’s service life.
