Can Ethernet Cables Start a Fire – An Electrician Weighs In

Ethernet cables are frequently ran through walls, under carpets, and under baseboards. Often times little thought is given to the potential safety implications that could result. Ethernet cables are categorized as low voltage wiring according to the national electric code (NEC). This means that they are not subject to the same set of rules and regulations as high voltage wiring. Anytime there is electricity there is always the concern about fire. Can ethernet cables start a fire? We checked with a licensed electrician.

Yes, an ethernet cable can potentially start a fire. However, the risk is extremely low when compared to other kinds of wiring. The voltage and amperage carried by an ethernet cable is very low. This is why ethernet cabling is not considered a high risk for causing a fire. However there are circumstances where an ethernet cable could become a fire danger.

Ethernet Cable Start Fire

Do Ethernet Cables Even Carry Electricity

On a technical level, yes, ethernet cables commonly carry electricity. Standard ethernet applications use a voltage of about 2.5 volts across the wire pairs. This is little more than the voltage of a standard 1.5 volt battery. 2.5 volts is not enough to produce any kind of spark.

The exception to this rule is for devices that use power over ethernet (PoE). PoE is most commonly used in commercial applications for powering devices such as wireless access points or PoE security cameras. PoE uses a max voltage of 48 volts DC. This is low enough to not be a danger and to still be categorized as low voltage wiring.

PoE also uses a handshake procedure to ensure the connected device is ready to receive PoE. If the PoE handshake fails for any reason such as a damaged ethernet cable, PoE will not turn on. This means that PoE has an added layer of protection against frayed or damaged cables.

Do Ethernet Ports Carry Electricity

Can Ethernet Cables Heat Up in Normal Use

The current levels carried by an ethernet cable is in the milliamp range. This means that there is not enough current to produce any meaningful amount of heat within an ethernet cable. The PoE standard does allow for about half of an amp of current. This is unlikely to be enough to seriously heat up an ethernet cable, even when ran under a carpet or other obstruction.

If you are using PoE, avoid using flat ethernet cables as they have the greatest chance of heating up during use. This is especially true of running the cable under a carpet or other flammable materials. However, even if the cable does get warm, it would not be nearly hot enough to start a fire.

Are Damaged Ethernet Cables a Fire Risk

Damaged ethernet cables are not a fire risk. That said if a cable is damaged, just replace it. With data wiring you are likely suffering from performance issues long before the cable looks noticeably damaged. In fact your ethernet connection may be running at 1/10 of its rated speed if the cable is damaged. Frayed wires and missing insulation though still do not pose any real fire risk.

A direct short across two or more of the wires in a Cat 5, Cat5e, Cat6, or Cat6a ethernet cable supplying PoE will generally damage the equipment on one or both ends of the cable. The cable is however unlikely to heat up by any significant amount in the short time it takes to have the ethernet port at either end fail.

Can an Ethernet Cable Shock You

According to the Institute of Electrical and Electronics Engineers (IEEE) standard ethernet protocols use a voltage of about 2.5 volts across the wire pairs. This is little more than the voltage of a standard 1.5 volt battery. 2.5 volts is not enough to feel, let alone be dangerous.

With PoE the is the potential for 48 volts to be carried though an ethernet cable. However the handshake procedure used by modern PoE standards means that you would have to touch the wire without disconnecting it from either device. This makes coming in contact with PoE voltage fairly unlikely.

Even if you did manage to come in contact with the 48 volts. you are unlikely to feel anything more than a slight tingle. The risk would be increased if you were standing in water, barefoot, or had a heart condition. 48 volts is classified as low voltage because it is generally not dangerous to humans. The fact that it is DC voltage and not AC voltage also make PoE significantly less dangerous.

How Could an Ethernet Cable Actually Start a Fire

As low as the risk of an ethernet cable starting a fire is, the risk is not zero. There are two scenarios where an ethernet cable has the potential to carry enough power to cause an electrical fire. The first situation and probably the most likely is from a lightning strike. This is extremely unlikely to result in the ethernet cable starting a fire. The more likely situation is that the equipment on each end of the cable gets damaged and the cable is perfectly fine. Even if the cable does get damaged, the actual fire risk is very low.

The other scenario which is even more unlikely, is if the ethernet cable comes in direct contact with a 120 volt or higher electrical wire. This would require the insultation on both the ethernet cable and the high voltage wire to be damaged and exposing the metal wire. This is most likely if the wires were running together though a conduit. It is never a good idea to run low voltage data wiring directly alongside high voltage AC wiring anyways. It is a recipe for interference in your data signal. The fire risk is just one more reason that low voltage and high voltage wiring should be kept separate.

Can Ethernet Cables Burn in a Fire

The jacket of a standard ethernet cable is made of PVC. PVC will burn when exposed to fire and release highly toxic fumes. Plenum rated ethernet cables have a special insulation that does not give off toxic fumes when exposed to fire.

Plenum cable is required by code when being installed in any “air handling” space. For example, this could include within air ducts or even above a drop ceiling. many large buildings use the space above the drop ceiling to return air to the HVAC units. This makes the ceiling a plenum, and therefore all the cables that go through the ceiling must be plenum rated.

Generally Cat 5e or Cat 6 cables which are plenum rated cost more than non plenum rated cables. Check your local building codes to determine if you need to use plenum cables. For patch cables that are not run through walls or ceilings, plenum cables are not required.

Ethernet Cable Burn in FIre

How to Reduce Ethernet Cable Fire Risk Even Further

  1. Connect all equipment to a proper surge protector with adequate capacity.
  2. Avoid running ethernet cables under carpets or other flammable materials.
  3. Avoid using flat cables if you are installing a device that uses PoE.
  4. Use plenum rated cables if required by code to protect yourself from toxic fumes should a fire occur.
  5. Do not run ethernet cables directly alongside high voltage wiring especially in conduits

Best Ethernet Cable Options

Best Patch Cables: Monoprice Cat6a Cable – This cable is much thinner than a regular Cat6a cable, comes in a variety of lengths and colors, and offers a great value.

Best Bulk Cable: Celertec CAT6A 500 Feet – Ethernet cable is tested to 650MHz bandwidth. Perfect for 10Gb network up to 328ft. Future proof your network with Cat 6a certified cabling.

FAQ

Can an Ethernet cable be hit by lightning

Absolutely, an ethernet cable can get hit by lightning. If an ethernet cable gets hit by lightning, in all likely hood any device connected to the cable will be damaged. It could be just the port that the cable was plugged into, or it could be the entire device, A surge protector is your best defense.

Can you get shocked by ethernet cable

No, Standard ethernet protocols use a voltage of about 2.5 volts across the wire pairs. This is little more than the voltage of a standard 1.5 volt battery. 2.5 volts is not enough to feel, let alone be dangerous. PoE uses 48 volts which is also unlikely to shock you.

Do Cat 6 cables carry power

On a technical level, yes, Cat 6 cables commonly carry electricity. Standard ethernet applications use a voltage of about 2.5 volts across the wire pairs. PoE uses a max voltage of 48 volts DC. This is low enough to not be a danger and to still be categorized as low voltage wiring. Cat 6 cables carry power but not enough to generally be dangerous to humans.

Do power cables interfere with ethernet

Yes, power cables absolutely interfere with ethernet signals. You do not want to run your power and data within about 1 foot of each other. It is especially a bad idea to run them together through the same conduit. This will increase the risk for interference greatly. Keep high voltage and low voltage data cables away from each other at all costs.

Is PoE a fire hazard

No PoE is not a fire hazard. PoE uses a low enough voltage and low enough current (amperage) that it is not considered to be a fire hazard. PoE is considered low voltage by the national electric code NEC and the electric codes of most regions. Ethernet cables carry a max of 48 volts when supplying PoE to a device. PoE is not a fire hazard.