Assuming an AFCI works does as advertised...

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GoldDigger

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Will an AFCI work with the K&T or for that matter the old 2 wire romex? Baring any neutral sharing or GFs.
I see no reason why it should not. The only question is what exactly could cause a parallel arc in K&T construction.
A series arc should be no different at all.
As you say, assuming that there are no topology issues like globally shared neutrals to prevent the GFP element of some AFCIs from holding.
 

mbrooke

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AFCIs that have GFP will probably not work as the GFP was added in order to pass UL 1699 testing which involves the EGC for NM wire. So the most logical assumption is that arc logic may not be advanced enough.


Now, AFCIs that do not have GFP (like GE) do not rely on the EGC to detect arcs so in theory they will work perfectly fine on two wire circuits.
 

bphgravity

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Florida
Will an AFCI work with the K&T or for that matter the old 2 wire romex? Baring any neutral sharing or GFs.

Of course... In fact, existing homes with antiquated wiring systems are most vulnerable to arcing-faults.

The CPSC has remarked that the frequency of fires in residential electrical systems is disproportionately higher in homes that are more than 40 years old. The CPSC also estimates that half of the home fires reported each year could be prevented by AFCI protection.
 

don_resqcapt19

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...
The CPSC has remarked that the frequency of fires in residential electrical systems is disproportionately higher in homes that are more than 40 years old. The CPSC also estimates that half of the home fires reported each year could be prevented by AFCI protection.
Their information shows that 85% of the dwelling unit fires that are said to be of electrical origin occur in dwellings that are least 20 years old. That is the reason why you will not see a big reduction in dwelling unit electrical fires for many years, and that assumes that the AFCI can prevent the typical dwelling unit electrical fire.

I think that the CPSC estimate of preventing 50% is extremely inflated. That is based on the opinion that most dwelling unit electrical fires are the result of joule heating, something that no device on the market can detect and clear.
 

romex jockey

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Insurance companies are demanding K&T removal with the threat of policy cancellation

Many states are also following suit.

As far back as 16 years ago i made a strong argument for AFCI protected K&T (as well as it's tagged on BX)

This was based on manufacturers claims

Since that time i've informed many distraught customers to pursue this 'fix'

I have not, since that time, know or heard of ONE insurance company backing AFCI technology for K&T protection

That said, i have not yet referred them all to the NEMA AFCI task force and/or CSPC members , perhaps they could grace us with an 800 #?

~RJ~
 

growler

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Atlanta,GA
Will an AFCI work with the K&T or for that matter the old 2 wire romex? Baring any neutral sharing or GFs.

Of course... In fact, existing homes with antiquated wiring systems are most vulnerable to arcing-faults.


Other than all the assumming and estimating and such is there anyone actually installing AFCI protection in a controlled number of older homes and keeping tabs on how well they perform?

You know the old saying of " don't call him a cowboy until you see him ride" or "the proofs in the pudding".
 

mbrooke

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Insurance companies are demanding K&T removal with the threat of policy cancellation

Many states are also following suit.

As far back as 16 years ago i made a strong argument for AFCI protected K&T (as well as it's tagged on BX)

This was based on manufacturers claims

Since that time i've informed many distraught customers to pursue this 'fix'

I have not, since that time, know or heard of ONE insurance company backing AFCI technology for K&T protection

That said, i have not yet referred them all to the NEMA AFCI task force and/or CSPC members , perhaps they could grace us with an 800 #?

~RJ~



K&T is NOT a problem. In fact 3 far greater issues exist:

1. Single stranded aluminum wiring

2. Early cloth NM that often has insulation that becomes brittle and fails.

3. BX cable. It has no bonding strip, and during a fault becomes an in wall heater.
 

bphgravity

Senior Member
Location
Florida
K&T is NOT a problem. In fact 3 far greater issues exist:

1. Single stranded aluminum wiring

2. Early cloth NM that often has insulation that becomes brittle and fails.

3. BX cable. It has no bonding strip, and during a fault becomes an in wall heater.

And AFCIs are a great solution to all these wiring method problems as well...
 

growler

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Location
Atlanta,GA
Down with AFCI's .

Bring back the Edison Fuse .




Don

Fuses actually offer arc fault protection in some cases :eek::eek::

http://paceforensic.com/pdfs/Circuit_Breakers_The_Myth_of_Safety.pdf


Many people started to consider fuses unsafe but that was not the problem.

The problem with fuses is they were to darned easy to tamper with.

I have been in homes where every fuse was a 30 amp.

I overherd a sales person at HD trying to sell a homeowner a 30 amp fuse because her 20 amp fuse keeps blowing.

With the right fuses installed a fuse panel is perfectly safe.
 

mbrooke

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Many people started to consider fuses unsafe but that was not the problem.

The problem with fuses is they were to darned easy to tamper with.

I have been in homes where every fuse was a 30 amp.

I overherd a sales person at HD trying to sell a homeowner a 30 amp fuse because her 20 amp fuse keeps blowing.

With the right fuses installed a fuse panel is perfectly safe.


Im willing to bet that even with 30amp fuses its still safe. A lot of people began sticking pennies behind them, and the boxes often had a few circuits which lead to some wonky solutions.

But I do agree, there seems to be big push to get rid of them when IMO they are superior to circuit breakers.
 

user 100

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texas
And AFCIs are a great solution to all these wiring method problems as well...

Bph, most al wiring failures in a home are the result of glowing connections-something which the afci does nothing about. You can tighten the old pre-8000 solid al around the screw of incompatible alloy to where its tight, but it will begin to creep and during this phase it will almost never arc-it just very slowly deforms and loosens up under load eventually glowing. We already have reliable fixes for this problem. Gfci or lowered magnetic trip would effectively take care of the unbonded bx issue and ditto for the old nm.
 

growler

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Atlanta,GA
Im willing to bet that even with 30amp fuses its still safe.


I don't know about that. I had to rewire a house that had 30 amp fuses but it was a strange situation. They had hooked the circuits up much like a British ring circuit. one circuit hooked up to two seperate fuses ( one at each end of the circuit). I don't know if this was an accident or if they ment to do it that way. There were two circuits done that way and a lot of melted insulation.

There was smoke but no real fire. It was summer, the wiring was 1930s vintage and that burned rubber smell was something else.
 

user 100

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Location
texas
I don't know about that. I had to rewire a house that had 30 amp fuses but it was a strange situation. They had hooked the circuits up much like a British ring circuit. one circuit hooked up to two seperate fuses ( one at each end of the circuit). I don't know if this was an accident or if they ment to do it that way. There were two circuits done that way and a lot of melted insulation.

There was smoke but no real fire. It was summer, the wiring was 1930s vintage and that burned rubber smell was something else.

Sounds like the old fused neutral setup common in vintage discos.
 

mbrooke

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I don't know about that. I had to rewire a house that had 30 amp fuses but it was a strange situation. They had hooked the circuits up much like a British ring circuit. one circuit hooked up to two seperate fuses ( one at each end of the circuit). I don't know if this was an accident or if they ment to do it that way. There were two circuits done that way and a lot of melted insulation.

There was smoke but no real fire. It was summer, the wiring was 1930s vintage and that burned rubber smell was something else.


ID guess that wire really took some overload. Ive seen a lot of #14 fused at 30amp and outside of light fixtures it generally doesn't appear to be a problem. NEC ampacity tables are very conservative.

Not that we should fuse #14 at 30 but my point is typical over fusing rarely leads to fire.

I am still convinced that 90 to 95% of all electrical fires come from high resistance connections (failed splices) and have nothing to do with arcing or overloads like we are lead to believe.
 
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