ECN Forum Forums General Topics of the Trade General Discussion Area AFCIs and series arcing faults

Sparky,
The standard AFCI has a GFP circuit in it, but it is not a combo device as the ground fault trip is 30 to 50mA. It appears that in many cases, the GFP part of the AFCI breaker will clear the fault, not the AFCI part. I believe that CH does have a combo device that is dual listed as both AFCI and GFCI.

I don't see how the manufacturers can use this premise to claim that the AFCI "detects" a series arc.

It'd be like a doctor saying "Yes, I can diagnose a common cold, but you'll have to wait for it to turn into pneumonia first."

If I invented a new wonder drug that would instantly cure pneumonia, wouldn't it be OK to say that it will also cure pneumonia that begins as a common cold?

Seriously, most "hot spots" that I have encountered in appliance cords have developed either near the plug, or at the appliance end, where most of the flexing occurs during use.
Individual strands break until there are only a few conducting, and finally they let go and one of the conductors opens. It would be a quite a coincidence if both conductors were to break at the same time.
I believe that most appliance cord failures begin as series arcs. Fortunately, it is difficult to maintain a series contact arc. Usually the device stops working and this results in the required repairs being done.

My wife is complaining that she has to hang the iron cord a certain way to get the iron to heat up, so I guess I had better go fix it before it develops into a parallel arc.

Ed

Maybe someone should come up with a receptacle that senses heat at the terminal and sends a digital signal to an X-10 circuit breaker telling it to shut off. That would not be a horrible idea for bedroom circuits. Loose terminals under load melt receptacles. I saw this first hand at an apartment building complex. The construction crew was doing the apartment upgrade including the electric. 1 circuit had two A/C's plus the load of the other 3 bedrooms. They hooked the conductor to the receptacles but never tightened the connections. The receptacle next to the young boys bed melted. The plastic was actually running down the outlet. Luckily the wire burned open and stopped the fire. If receptacles sensed heat by the terminals this would have been prevented. Of course the contractor would have never used them in the first place...

Don,
i posted as example of the double talk the manufacturer's tend towards, which i'm really getting tired of.

note UL1699 uses a guillotine type device across NM , 3 wire....the idea of a series arc of any progressing into a parralell fault becomes realistic due to the proximity x magnitude.

this does not exist for K&T.....which i'm installing AFCI's on....

so the perfect 'lab' scenario then has wide variables in the real world, Ed's original post is greatly compromised.

the efficy falls off the bell curve.....

there will be no change in the previous 'hot spots' the K&T has had....

I have just installed GE type AFCI breakers.
When I turned it on it tripped right away.I checked for neutral to groung contact and for shorts. I turned off the light switches reset the breaker it stayed on. As soon as i turned on one of the light switches the AFCI tripped. I started taking apart light fixtures nothing obvious. I called a friend of mine and he said test install a regular breaker and see if it trips voila all lites were on and no tripping. I did notice a loose connection under one of the wire nuts for the hots. I tightened and reinstalled the GFCI breaker and everything worked fine since. I guess my question is was this supposed to happen
?

correction reinstalled the AFCI breaker

One thing to consider with the new "device model" is whether it will survive a bolted fault. I know <from experience> that is usually the kiss of death for a device GFCI. They also fail "closed". I assume the relay contacts weld. I even had one go when the fault was just a light bulb with a standoff failure.