Detection Of High Resistance Connections (HRCs)

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ptonsparky said:
How can they? Those connections will appear as a load. A .2 amp current means nothing to a 20 amp breaker but means 96 watts at that poor connection.
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96 watts is a lot of heat in say the small space of a wire nut. Pencil type soldering irons are usually only in the 10 watt range.

Still AFCI's or other similar attempts to detect this from the load center and not right at the connection in question are only going to see it as load like you said.
 
My biggest concern is a 90 year old Greenfield/BX cable conductor insulation breaking down in someone's home. No way to detect it until it's too late.
 
a GFCI won't detect a 5 mA Hot to Neutral ground fault current.
It will only detect an insulation failure to something bonded to the Safety Ground (EGC).
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an AFCI is a different story.
 
thinking about it more:
a GFCI will also detect current leaking to or from another circuit's Hot or Neutral.
 
Speedskater said:
a GFCI won't detect a 5 mA Hot to Neutral ground fault current.
It will only detect an insulation failure to something bonded to the Safety Ground (EGC).
* * * * * * * * *
an AFCI is a different story.
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Yes, I know that, but the line to neutral fault will very often create enough heat and damage the insulation enough to create a ground fault.
In talking with one engineer who worked on the AFCIs, it was his opinion that the GFP in the original AFCIs did much more of the work than the arc recognition algorithm, however the GFP is not found in a number of the currently available AFCIs.
 
don_resqcapt19 said:
but it is possible the heat will cause a 5 mA ground fault before there is a fire.
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My first experience a few years ago where I thought an AFCI was possibly doing what it is supposed to do involved a melting down receptacle where user had been using a portable space heater. But after further investigating the receptacle had developed a high resistance ground fault. The AFCI was QO series which has integral 30 mA GFP as part of it's design. I would guess that GFP feature caused the trip more so than the AFCI feature of the breaker.
 
kwired said:
My first experience a few years ago where I thought an AFCI was possibly doing what it is supposed to do involved a melting down receptacle where user had been using a portable space heater. But after further investigating the receptacle had developed a high resistance ground fault. The AFCI was QO series which has integral 30 mA GFP as part of it's design. I would guess that GFP feature caused the trip more so than the AFCI feature of the breaker.
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Exactly. None of the original branch circuit/feeder type AFCIs could pass all of the required tests in the product standard without a GFP as part of the device. Now apparently they have found ways to pass the required testing without the additional expense of the GFP circuit.
I think that was a step backwards as it is my opinion that about 80% of the AFCI trips were really GFP trips.
 
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