Close call residential electrical accident that really deserves a full investigation

[Electric-Light]

A case of potentially deadly near miss electrical accident in 2016 in New York apartment.
(tenant victim)
Possible causes (apartment maintenance, property management, handyman, service technician, cable internet provider, Satellite installation)

It's pretty common to have several amps through coax due to dozens of mV of ground voltage differential shorting through milliohms of impedance but here, Theverge editor sustained equipment damage and shock from dangerous levels of voltage between communication lines and EGC at his New York apartment. https://www.theverge.com/2016/5/18/11705038/cablevision-coax-destroyed-tv-nearly-killed-me

Chris Welch, an editor for Theverge reported fireworks and molten HDMI cable connector when the shielding shell joined the two chassis' electrically and triggered a fault current. He reports he received nastiest shock he's had in years and reported it destroyed two TV sets and a cable box in the process. He states he's had his TVs and Optimum Cable for years but problems apparently happened shortly after a separate satellite installation was added.

This destroyed two TVs in two separate occasions and the cable box Later investigation found staples used by installer damaged the shealth on the cable. This could have been irrelevant superficial damage or this could have severed the hot conductor inside the wall and made an intermittent short that didn't show symptoms but completed the circuit when he moved the wires around.

Chris shows a video made during a troubleshoot visit by an unnamed satellite provider and it shows sparks flying after slapping the coax head into some kind of AV equipment chassis that is presumably tied to receptacle ground.

This is a case where one of the chassis in a set of chassis' that are all supposed to be at the ground potential lit up with utility power somehow and caused a shock accident and property loss.

From my experience, modern TVs use the same IEC power cord used for desktop computers and plug into a 3-prong outlet and chassis tied to the power EGC. Cable box, VCRs and disc players often use two prong or AC adapter with no electric side grounding but chassis tied to the shell of coax input.

Satellite was the latest addition and it's the most probable piece that can island at 120v without tripping anything essentially making the antenna a lightning rod that is ungrounded and bridged to 120v hot by a staple, but it could also have been a grounded outlet that somehow got bonded to hot. This example is a good example in support of requiring some sort of licensing for communication installers.

 

[ramsy]

A case of potentially deadly near miss electrical accident ..It's pretty common to have several amps through coax

I've called the power company several times to fix similar issues, since NFPA-70 jurisdictions bond all services, including structured wiring, power, water, & Gas, to the same Grounding-Electrode-System (GES).

When a utility provided, power-line Neutral is cut, broken, interrupted or opened, by design the building's main-bonding jumper already ties neutral to grounding, and the Grounding-Electrode System becomes the return path for building power, including all phone & cable D-marc's, until people get electrocuted, appliances burn up, or buildings burn down.

 

[mbrooke]

I've called the power company several times to fix similar issues, since NFPA-70 jurisdictions bond all services, including structured wiring, power, water, & Gas, to the same Grounding-Electrode-System (GES).

When a utility provided, power-line Neutral is cut, broken, interrupted or opened, by design the building's main-bonding jumper already ties neutral to grounding, and the Grounding-Electrode System becomes the return path for building power, including all phone & cable D-marc's, until people get electrocuted, appliances burn up, or buildings burn down.

Which is why neutral should be kept isolated all the way back to the transformer X0. But cost says otherwise.


FWIW when I unhook my Cox line at the grounded splitter in my basement I get something like 90 volts and a good tingle. My 2 wire router and cable box apparently leak to the shield. :rant:

 

[GoldDigger]

... FWIW when I unhook my Cox line at the grounded splitter in my basement I get something like 90 volts and a good tingle. My 2 wire router and cable box apparently leak to the shield. :rant:

Which leads me to wonder whether the wall wart or power cord to the equipment is reversible?
In some cases the problem could be noise suppression capacitors from power line to ground inside the equipment.

 

[mbrooke]

Which leads me to wonder whether the wall wart or power cord to the equipment is reversible?
In some cases the problem could be noise suppression capacitors from power line to ground inside the equipment.

Well, it is on one Although I think it shouldn't do that. My understanding is that UL actually performs revere polarity testing. But if it leaks that much, in the minimum I'd thing an EGC is in order.