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Old 07-15-2012, 11:09 PM   #31
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Whole house surge protector - no extra breakers


I also recommend the 2 surge guides in a post by surgeknowitall.
He has a link to the IEEE surge guide:
http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf

NIST's "Surge Happens" is at:
http://www.eeel.nist.gov/817/pubs/sp...%20happen!.pdf

Quote:
Originally Posted by westom View Post
Not true anywhere in North America. Those lines have always been required to be surge protected by many codes.
The IEEE surge guide, starting page 30, shows a cable entry ground block with a ground wire to the building power earthing system that is too long. With a surge to cable, the voltage from cable to power wiring is 10,000V. (The section is ground potential rise - as in surgeknowitall's post.) Many houses have phone or cable entry points too far from the power service, and the earthing system.

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Originally Posted by westom View Post
What is the best protector on coaxial signal wire? The 'required by code' wire from that cable to earth ground.
The NEC just requires a ground block at the coax entry that allows the coax shield to be earthed.

The IEEE guide says “there is no requirement to limit the voltage developed between the core and the sheath. .... The only voltage limit is the breakdown of the F connectors, typically ~2–4 kV.” And "there is obviously the possibility of damage to TV tuners and cable modems from the very high voltages that can be developed, especially from nearby lightning."

Quote:
Originally Posted by westom View Post
How good is that protection? Well, how good is the earth ground?
Suppose you have someone's near miraculous 5 ohms resistance to earth, and the system earths a 2,000A surge. The building 'ground' system will be 10,000V above 'absolute' earth potential. If the earthing electrode was a ground rod, in general 70% of the voltage drop away from the rod is in the first 3 feet. The earth more than 3 feet from the rod will be at least 7,000V from the building ground. One place that can show up (as noted in the IEEE surge guide) is at a pad mounted A/C compressor/condenser that is pad mounted on earth distant from the grounding electrode. The compressor (at earth potential at the pad) will be far from the power wiring (at earth potential at the power earthing system). The impedance of the power ground wire to the compressor won't help much. (A surge is a very short event which means it has relatively high frequency current components, which means the inductance of the wire is much more important than the resistance.)

The author of the NIST surge guide has written "the impedance of the grounding system to `true earth' is far less important than the integrity of the bonding of the various parts of the grounding system."

Worry about the length of the ground wire from cable and phone entry protectors to the common connection point on the power earthing system. The NIST surge guide suggests that the major cause of equipment damage is high voltage between power and phone/cable/... wires. Much of the protection is actually that all the wiring (power/phone/cable/...) rises together.


The author of the NIST surge guide also looked at surges on power service wires. He found the maximum surge on a residential power service that has any reasonable probability of occurring is 10,000A per wire. That is based on a 100,000A lightning strike to a utility pole adjacent to a house. Service panel protectors with higher ratings just give long life. Recommendations for ratings are in the IEEE surge guide on page 18.

Service panel protectors are very likely to protect anything connected only to power wires from a very near very strong lightning strike. They may or may not protect equipment connected to both power and phone/cable/... wires.

Quote:
Originally Posted by westom View Post
It can never be repeated enough. Either a surge is earthed harmlessly outside the building. Or that surge will hunt for earth ground destructively via appliances.
Outside the question that was asked, but both the IEEE and NIST surge guides say plug-in protectors are effective. If using them all interconnected equipment needs to be connected to the same protector. External connections, like coax also must go through the protector.

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Last edited by bud--; 07-15-2012 at 11:13 PM.
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Old 07-15-2012, 11:48 PM   #32
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Whole house surge protector - no extra breakers


Quote:
Originally Posted by bud-- View Post
I also recommend the 2 surge guides in a post by surgeknowitall.
He has a link to the IEEE surge guide:
http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf

NIST's "Surge Happens" is at:
http://www.eeel.nist.gov/817/pubs/sp...%20happen!.pdf


The IEEE surge guide, starting page 30, shows a cable entry ground block with a ground wire to the building power earthing system that is too long. With a surge to cable, the voltage from cable to power wiring is 10,000V. (The section is ground potential rise - as in surgeknowitall's post.) Many houses have phone or cable entry points too far from the power service, and the earthing system.



The NEC just requires a ground block at the coax entry that allows the coax shield to be earthed.

The IEEE guide says “there is no requirement to limit the voltage developed between the core and the sheath. .... The only voltage limit is the breakdown of the F connectors, typically ~2–4 kV.” And "there is obviously the possibility of damage to TV tuners and cable modems from the very high voltages that can be developed, especially from nearby lightning."



Suppose you have someone's near miraculous 5 ohms resistance to earth, and the system earths a 2,000A surge. The building 'ground' system will be 10,000V above 'absolute' earth potential. If the earthing electrode was a ground rod, in general 70% of the voltage drop away from the rod is in the first 3 feet. The earth more than 3 feet from the rod will be at least 7,000V from the building ground. One place that can show up (as noted in the IEEE surge guide) is at a pad mounted A/C compressor/condenser that is pad mounted on earth distant from the grounding electrode. The compressor (at earth potential at the pad) will be far from the power wiring (at earth potential at the power earthing system). The impedance of the power ground wire to the compressor won't help much. (A surge is a very short event which means it has relatively high frequency current components, which means the inductance of the wire is much more important than the resistance.)

The author of the NIST surge guide has written "the impedance of the grounding system to `true earth' is far less important than the integrity of the bonding of the various parts of the grounding system."

Worry about the length of the ground wire from cable and phone entry protectors to the common connection point on the power earthing system. The NIST surge guide suggests that the major cause of equipment damage is high voltage between power and phone/cable/... wires. Much of the protection is actually that all the wiring (power/phone/cable/...) rises together.


The author of the NIST surge guide also looked at surges on power service wires. He found the maximum surge on a residential power service that has any reasonable probability of occurring is 10,000A per wire. That is based on a 100,000A lightning strike to a utility pole adjacent to a house. Service panel protectors with higher ratings just give long life. Recommendations for ratings are in the IEEE surge guide on page 18.

Service panel protectors are very likely to protect anything connected only to power wires from a very near very strong lightning strike. They may or may not protect equipment connected to both power and phone/cable/... wires.



Outside the question that was asked, but both the IEEE and NIST surge guides say plug-in protectors are effective. If using them all interconnected equipment needs to be connected to the same protector. External connections, like coax also must go through the protector.
Let's come back down to earth here... This all started when I said that no matter what fancy surge protector one installs...it is virtually useless without an adequate ground system. (Some readers laughed, but now their not...) such is life

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