Sparking at a comcast cable outlet

stew

Senior Member
Have a troubleshoot to do tomorrow in a home that is a hybrid in that there are some circuits from the service panel that have been added over the years and are grounded but there are still several KT circuits. still in use. Nearly all the outlets that I saw were replaced with 3 wire outlets for convenience which of course isnt cool including many on KT circuits. Problem is when comcast tries to install a cable upstairs in one room when they plug in thier cable they get big time sparks. Last time I had one of these it turned out to be H/N swapped on a KT and a bootleg ground picking up voltage. At least thats what I recollect. Any thoughts?
 

GoldDigger

Moderator
Staff member
The cable is connected to earth ground or whatever approximation of it is present at the Comcast entrance box.
That could be different from the local ground at the receptacle if either of either of them is abnormal
Just measure the voltages to a common reference point.

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ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
Have a troubleshoot to do tomorrow in a home that is a hybrid in that there are some circuits from the service panel that have been added over the years and are grounded but there are still several KT circuits. still in use. Nearly all the outlets that I saw were replaced with 3 wire outlets for convenience which of course isnt cool including many on KT circuits. Problem is when comcast tries to install a cable upstairs in one room when they plug in thier cable they get big time sparks. Last time I had one of these it turned out to be H/N swapped on a KT and a bootleg ground picking up voltage. At least thats what I recollect. Any thoughts?
Had a similar situation occur a month or so ago. A power strip had an internal fault hot to EGC but the EGC prong was broke inside the molded cord. Computer and printer were plugged into it. Tech dude went to plug in something, I think it was a HDMI and drew a big spark. He left in a huff. I fixed it and got cookies.

Best thing I know to do is test suspect recpts against an extension cord powered by a recpt that is known to be wired correct, even if you have rig one up at the panel.
 

GoldDigger

Moderator
Staff member
this may be a long day to find. hope not!
A long extension cord or wire to use as a constant ground voltage reference throughout the house will go a long way to tracking the problem down. Once you have done that you can hope that the issue is in a j-box or at a device rather than in the wall.
 

stew

Senior Member
turns out this was an old fuse service that had been replaced in the 70s with a federal pacific panel. The main bondiong jumper to the cold water pipe located just inside the wall adjacent was not reconnected to the panel but was just dangling against the exterior of the panel. The little jumper connection that is used to bond the neutral to the panel was left laying in the bottom of the box. The comcast folks had run a # 12 at some time from thier equipment thru the side of the house above the panel and had installed a bonding ground clamp to the cold water pipe. The only ground reference this install had was comcast!. Bonded the 2 water pipes. Bonded from the panel to the water pipes. . Bonded the neutral inside the panel. Guess what? All is 0 volts now and works just fine.So much fun to pick up behind whomever installs stuff without any knowledge of what they are doing!!
 
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