Phone line grounding

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  #1  
Old 09-17-05, 09:24 AM
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Join Date: May 2003
Location: USA
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Phone line grounding

We just had a new phone line installed the other day and the phone tech grounded it to the home's electrical system ground rod.

Is this OK? I thought I had read that the phone line should be grounded seperately from the electrical, but I wanted to hear from you all first. Seems to me that any fault would pass through the ground system, and into the phone line where it could damage anything the line is connected to.

If it is OK however, can I do the same for the cable line and connect it to the ground rod as well?

Thanks for setting me straight on this.
 
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  #2  
Old 09-17-05, 09:31 AM
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The connection is correct.

Do not touch the cable line. The grounding for that is the responsibility of the provider, not the user. They should have already properly grounded it.
 
  #3  
Old 09-17-05, 12:29 PM
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I quote from, refer to, the 2005 NEC "Handbook", pages 220-221.

"The reason for the potential hazard is illustrated in Exhibit 250.39 ( a drawing) which shows a CATV cable with it's jacket Grounded to a seperate Ground rod and not Bonded to the power Ground"

"the solution is to Bond the two Grounding Electrodes together as shown in Exhibit 250.40, or to connect the jacket of the CATV cable to the power Ground, which is exactly what the Code requires."

Let's presume the resistance -to -earth of the "power" Grounding Electrode is 25 Ohms, and a "surge" current of 100 amps is conducted thru the Grounding Electrode. The voltage across the Grounding Electrode resistance is 25 X 100 = 2500 volts.

Connected indirectly to The "exposed, acessible end" of the "power" Grounding Electrode is the Equiptment Grounding Conductor of the receptacle into which the cord of a TV receiver is "plugged".

If the metallic "sleeve" of a CATV cable is connected to a seperate Grounding rod, then it's also indirectly "connected" to the "earth side" of the "power" Grounding Electrode.Consequently,at the T.V receiver, there is a potential of 2500 volts between the EGC of the receptacle and the metallic "sleeve" of the CATV.

Bonding the CATV Ground to the same "point" of the power Grounding Electrode where the interior Grounding connections are directly/indirectly connected will eliminate the hazard.
 
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