Top 2 Things to Consider When Running Ethernet and Power Cable
Written by Don Schultz, trueCABLE Network Expert, BICSI INST1, INSTC, Fluke Networks CCTT
Have you ever wondered about the effects of running Ethernet cable next to power cable? How about running your Ethernet cable next to discreet (individual) high interference items like generators or fluorescent light fixtures? Read on to find out how to make your install safe while avoiding data loss with minimal additional hassle. We will also cover a number of best practices!
The top two things to consider are:
- Data integrity
Be careful of anecdotal evidence or advice! Anecdotal evidence from some (well meaning) individuals say running Ethernet cables or coaxial cable in parallel to electrical at closer distances causes no harm. In their case it likely did not or it went unnoticed at first, because the electrical wire was not being pushed to its amperage limit. So, in their particular situation at the time they stated this anecdotal evidence, this has become fact and they repeat it as such.
The fact is, the amount of interference that an electrical wire or other source emits will vary depending on what you have plugged into it, and when you are using the plugged in device.
There are rules for residential and commercial installations that have actual legal consequences attached to violating them (and recorded in the law as local Codes). Violate Code at your peril. There is an old, but apt saying: “Safety codes were written on top of bodies and property damage”. Following Code not only protects you, but helps ensure your communications cable will work the way you intended it to. Fines, loss of license, civil litigation, and even criminal charges await those who don’t obey the rules.
National Electric Code (NEC) / National Fire Protection Act (NFPA) Regulations
- Ethernet data cabling, coaxial cable, etc. is classified as a low voltage communications cable. Any type of AC wiring is classified as high voltage.
- When running unshielded communications cable parallel to typical residential voltage power cables (120V or 240V for example), the NEC (National Electric Code) specifies it must be separated by at least 200mm or 8 inches.
- The NEC further specifies that shielded low voltage communications cable may be run in parallel with common 120V and 240V AC wiring within 8 inches, but no closer than 2 inches.
- You may run low voltage communications cable over AC wiring at a 90 degree angle without restriction, but you should not allow the wires to physically touch. This is known as “crossing at right angles''.
It should be noted that this is to meet national U.S. building code. Most municipalities adopted this code without change. However, there are municipalities that have their own rules. It’s the installers responsibility to research this. When in doubt, always speak with your local Code Inspector.
The NEC is concerned with a natural phenomenon known as voltage induction. Voltage induction means voltage can actually transfer from one cable to another due to the magnetic field generated by the higher voltage cable. In the case of Ethernet data cabling, this would not be good. The effect would be a piece of sensitive electronic equipment receiving voltage when it should not, potentially causing a fire hazard or voltage strong enough to cause personal injury or even death.
The eight inch / two inch rule covers nearly all residential EMI/RFI issues. Things change, however, when it comes to extreme sources of interference found in some commercial spaces.
Voltage induction takes on a whole new meaning when extremely high voltage cabling like 480V or higher is involved. Situations like these require careful thought and installation practices. Lives and property are in danger if this is not handled by properly educated (preferably professionally trained) personnel.
Other Problem Areas
Avoiding areas of high interference (EMI/RFI) is not just about keeping a separation from AC wiring. It may also involve EMI/RFI sources like:
- High voltage electrical panels
- Induction heaters
- Fluorescent light fixtures
- Electrical motors
- Medical equipment
- Factory machines/equipment
These sources of high interference generate a “bubble” of EMI/RFI around them. This EMI/RFI bubble is a “keep out” zone. The size of the keep out zone can be reduced by using shielded cable. Making use of properly bonded and grounded metallic conduit will reduce the zone size further. It is all relative!
Representation of EMI bubble around a induction motor
Some areas of extreme interference may require a site survey to determine the “KEEP OUT” zone. Always consult a qualified electrician or professional who specializes in this type of analysis if in doubt.
In the table presented below we address both common situations and extreme situations and how to mitigate them while protecting your data. This table was developed from several sources including the NEC, ANSI/TIA, and BICSI. If any listed item conflicted on separation distance between one or more sources, the stricter distance limitation was used. No distinction is made between commercial or residential spaces, as the commercial space rules and recommendations were used.
General Guidelines for Safety and Communications Cable Data Integrity
*Frequency induction heating introduces other distance limitations such as induced by temperatures!
Best Practices When Dealing With RMI/EFI Sources
- Shielded pathways (ENT metallic conduit for example) and especially distance are your friends!
- Always properly bond and ground shielded communications cable or the cable shield will not function, rendering the Ethernet or coaxial cable effectively unshielded
- When using metallic conduit it should be properly bonded and grounded as well
- Using shielded Ethernet or quad-shield coaxial cable inside of metallic pathways is the most effective way to reduce EMI/RFI in extreme environments, in conjunction with distance
- If you are a residential installer, your local codes may not even address communications and AC wiring separation issues for single and duplex dwellings. If this is the case, follow the above guidelines as if they were Code. Your local inspector will likely thank you!
Following the safety and data integrity guidelines will allow for a cable installation that is not only safer, but less susceptible to data loss. Know your environment, take the correct precautions and consult a registered electrician or EMI/RFI specialist.
With that said, HAPPY (and safe) NETWORKING!
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