Low voltage cable differs from standard electrical wiring; meaning installers must operate under a different set of rules to protect themselves, the installation property, and the wiring. Factors like electromagnetic interference (EMI), cable durability, and data integrity all play roles in protecting low voltage wiring during installation and after.
Low Voltage Wiring Laws, Rules, & Regulations
Most municipalities have adopted the National Electric Code (NEC and National Fire Protection Act (NFPA) regulations. One of the main concerns covered by the NEC is voltage induction, the phenomenon where voltage is transferred from one cable to another due to the magnetic field generated by the higher voltage cable. This magnetic field will induce a voltage in any electrically conductive material within range.
This can cause a piece of sensitive electronic equipment to receive voltage through an ethernet cable when it should not; causing a potential fire hazard and jeopardizing data integrity. The higher the voltage of AC electrical wiring in a structure, the more careful you need to be when installing low voltage wiring.
Here are a few rules the NEC recommends installers to follow:
- Unshielded low voltage wire running parallel to standard high voltage wiring (120V and 240V) must be separated by at least 8 inches.
- Shielded low voltage wire may run parallel with the same high voltage wiring within 8 inches, but no closer than 2 inches.
- You may run low voltage wire over AC wiring at 90 degrees as long as they don’t physically touch.
- Do NOT run low voltage wiring through the same holes as high voltage lines.
Electromagnetic Interference (EMI)
Electromagnetic interference (EMI) is unwanted noise or interference in an electrical path or circuit caused by an outside source. In the case of low voltage wiring, the main culprit is usually AC electrical wiring. However, generators, transformers, electrical motors, and medical equipment can also be EMI sources.
Shielded Cable: What It Is And How It Works
The main way low voltage cables fight EMI is through shielding. Without shielding, cables can pick up energy from unwanted sources.
The following are the four common types of cable shielding:
- Copper Braid Shield: Also called metallic braid shields, they are formed from bare, tinned, or silver-plated copper strands braided into a mesh around the cable core. Copper braid shields are flexible and durable. Unlike foil shields, they cannot offer 100% coverage. Copper braid shield coverage is usually between 60 and 95%.
- Foil Shield: Foil shields are made of aluminum and ½ millimeter thick mylar composite tape to increase mechanical strength. They offer 100% coverage, easy termination, and the ability to be color coordinated.
- Spiral (Serve) Shield: Spiral shields are formed from bare, tinned, or silver-plated copper strands. These shields are used primarily in audio and microphone cables due to their flexibility.
- Combination Shields: Combination shields are formed with two or more shields combined in the same cable. These combinations can include braid over foil and braid over braid. They provide protection at both low and high frequencies
Does Low Voltage Wiring Need To Be In Conduit?
Conduit is a tube or trough used to protect electrical wiring. Conduit provides excellent protection from EMI and radio frequencies. Local codes may vary, however extra-low voltage (anything less than 50V) does not need to be in conduit. If the wiring will be exposed to heat, buried, or exposed to outside elements, then conduit is advisable to protect it.
Low Voltage Cable Management
Last but not least, cable management is an important piece of protecting low voltage cables. Low voltage cables are terminated in a box called a structured cabling enclosure. In business environments, wires may be terminated in a dedicated control room. In the control room, wires will terminate into patch panels, allowing them to be labeled, organized, and eventually managed. Unorganized cables lead to a “spaghetti” look that is unpleasant to the eyes and your bottom line.
Mismanaged structured cabling, which is an oxymoron in itself, will lead to downtime sooner or later.
Here are some best practices:
- Test all cables after they’re installed to remove excess or underperforming cables.
- Label types of cables and their location for future reference.
- Ensuring cables aren’t too long or short to avoid tripping, snagging, and pulling.
- Plan for future growth during your current installation and not after the fact.
- Organize all of your cables in a categorized excel spreadsheet or similar tracking tool. If the person who manages the cabling leaves, the new manager will need a way to get up to speed.
Follow these steps and your organization will enjoy a proactive network (rather than a reactive one) that experiences little downtime and network outages, increased lifespan, and better performance.
Oh, and one last thing about low voltage cable management…
It would be difficult for you to attempt to derive the best way to manage your structured cabling/network wiring from this blog post. Each structured cabling network is different based on the bandwidth needs, size of the building, and various other factors. Luckily, there’s a treasure trove of case studies on the internet with people sharing how they did their structured cabling.
Turning a jumble of low voltage wires into a structured cabling network is a worthwhile endeavor. Properly protecting and organizing your low voltage wiring infrastructure ensures that you minimize downtime and leave space for upgrades in the future. If you have questions about installing low voltage wiring and how to best protect it, reach out to the team at The Network Installers.