Testing Done by Legrand

Merry Christmas

mbrooke

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I wonder what is exactly happening in the test report then?

Bear with me-

The theory is that over driven staples break open the insulation on copper conductors in NM-B cables.

At 120 volts, electricity can not jump the millimeter gap between the hot and ground inside in NM cable.

However, lightning and switching transients cause multi killiovolt surges which leap across the gap between the damaged insulation on the hot and bare ground. Each mini arc creates a carbon path, whereby 120 volts can arc across this carbonized path on its own.

This 120 volt arc is called high current arcing, and its where AFCIs are supposed to come in, in the event the high current arcing happens to be below a breaker's magnetic pickup due to long run lengths.


With a surge arrestors, these high voltages are shunted preventing the over driven staple segment from acting as a spark gap. As such no carbonization will take place, and without a carbon path no high current arcing can take place.


I say theory, because it is just a theory created by UL that has never been actually confirmed as a mechanism of action in the real world.
 

mbrooke

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United States
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Technician
But, assuming this theory is true for the sake of argument- testing done by Legrand shows that a surge arrestor on every home would provide at least the same level of protection as an AFCI. In theory more so, because high voltage surges can damage an AFCI...
 

yuhong

Member
Location
Burnaby, BC
Bear with me-

The theory is that over driven staples break open the insulation on copper conductors in NM-B cables.

At 120 volts, electricity can not jump the millimeter gap between the hot and ground inside in NM cable.

However, lightning and switching transients cause multi killiovolt surges which leap across the gap between the damaged insulation on the hot and bare ground. Each mini arc creates a carbon path, whereby 120 volts can arc across this carbonized path on its own.

This 120 volt arc is called high current arcing, and its where AFCIs are supposed to come in, in the event the high current arcing happens to be below a breaker's magnetic pickup due to long run lengths.


With a surge arrestors, these high voltages are shunted preventing the over driven staple segment from acting as a spark gap. As such no carbonization will take place, and without a carbon path no high current arcing can take place.


I say theory, because it is just a theory created by UL that has never been actually confirmed as a mechanism of action in the real world.
In this case, they used an extension cord to test.
 

GoldDigger

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Placerville, CA, USA
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Retired PV System Designer
By joules they mean a high voltage surge of energy shunted by the arrestors.

Joule heating is where a high resistance at a splice causes current heating.

One words used to describe two different events.
The performance of a surge arrestor is limited by joule heating in the MOV or other conducting element. Too much and it melts, losing its ability to shunt overvoltage. Hopefully it has done its work before that point. That is the source of the energy rating of an SPD.
 

yuhong

Member
Location
Burnaby, BC
The performance of a surge arrestor is limited by joule heating in the MOV or other conducting element. Too much and it melts, losing its ability to shunt overvoltage. Hopefully it has done its work before that point. That is the source of the energy rating of an SPD.
The thermal fuse in the surge arrestor does not protect against things like overcurrent the way breakers do, right?
 

mbrooke

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Location
United States
Occupation
Technician
The performance of a surge arrestor is limited by joule heating in the MOV or other conducting element. Too much and it melts, losing its ability to shunt overvoltage. Hopefully it has done its work before that point. That is the source of the energy rating of an SPD.


Correct- my apologies. I thought Yuhong was referring to splices. My mistake.
 
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