What I learned from Sq D rep today

[LarryFine]

I believe that is a gfci characteristic an afci is a little more involved.

Oops! My bad. I missed the "a". :roll:

From what I've read, there is a micro-controller that recognized what is called the "signatutre", or characteristics, of the current of an arc. That's all I can tell you.

 

[LarryFine]

. . . the "signatutre" . . .

Would you believe "signature?" :roll:

 

[e57]

One other neat thing about the clear AFCI breaker is that you can see that the electronics trip the breaker mechanism with an old-fashioned solenoid pushrod.

I too think that is neat (a little shunt trip stuffed in ther - cute.) - as I am now 100% positive that they can reduce the cost per buy relocating all but the soloniod and the CT and have a single plug in unit to cover an entire panel. i.e. have a single more robust upgradable processor in the panel for sensing and triggering the trip mechanism. Hey at that point make a universal breaker - and have the processor gather information on the circuit and trip it if it goes outside of what it was programmed for... I'm calling it my dream panel...

 

[e57]

Both (or all three for a 2p unit) circuit conductors pass through a ferrite ring that has a smaller coil wrapped around it on one side. That coil feeds a circuit that feeds a magnetic tripping mechanism.

As long as the current is equal through all conductors, no magnetic field is induced in the small coil. If the flow isn't equal, a voltage is developed in the coil. When it reaches a set point, the mechanism trips.

Is this not the way a GFI works - my understanding is that all that electronic crap is sensing waveform distortion.... Analyzing - then give the no-go/go command to trip or not...

 

[LarryFine]

Both (or all three for a 2p unit) circuit conductors pass through a ferrite ring that has a smaller coil wrapped around it on one side. That coil feeds a circuit that feeds a magnetic tripping mechanism.

As long as the current is equal through all conductors, no magnetic field is induced in the small coil. If the flow isn't equal, a voltage is developed in the coil. When it reaches a set point, the mechanism trips.

Is this not the way a GFI works - my understanding is that all that electronic crap is sensing waveform distortion.... Analyzing - then give the no-go/go command to trip or not...

My description is indeed how a GFCI works; yours is how an AFCI works.

 

[don_resqcapt19]

... Did you know that QO stands for quick open?

The instantaneous trip of a QO is set at about 8 times the handle rating. Most others are set at about 12x. The UL standard does even require an instantaneous trip function so there is no rule on what the trip should be set at. I have been told that at least one breaker on the market has it set at 40x.

 

[Dennis Alwon]

I have been told that at least one breaker on the market has it set at 40x.

There was one on the market that has no instantaneous trip rating. It was FPE. :grin:

 

[Brady Electric]

What I learned from Sq D rep today

Good Post
Imformative
Don't use Sq D anymore because of the cost and I got mad at Graybar
I do think there the best
Years ago that's all I ever used and never had any trouble
Semper Fi Buddy

 

[jim dungar]

The instantaneous trip of a QO is set at about 8 times the handle rating. Most others are set at about 12x.

Only the QO(B) 1Pole 15 and 20A versions have the Qwick-Open characteristic, which according to their literature has a band of 8-10x handle rating. All of their other breakers have more traditional curves often starting at 10x or more.

 

[mark32]

They are partially wrong. QO does not stand for quick open, although 1P 15A and 20A QO breakers do have a Qwick-Open feature. I have technical information on QO breakers that goes back to the early 60's (they were introduced in the late 50's). This is definitely an "urban legend".

The first Square D residential breakers were type MO, then came the type XO, and finally QO. I have never found the proof but I believe this breaker should have originally been called Q-zero as the next breaker in the family was the Q1 (70-100A), followed by the Q2 (110-225A), and finally the Q4 (250-400A).

They were correct that the QO and HOM breakers have always had the same internal parts and tripping characteristics.

Thanks for the info. As far as Homeline and QO differences go, I've been under the impression that they have always had different internals. I think most believe this to be true, just read some of the posts here where someone would bash Homeline but praise QO. Also, the reps stated that the internals changed in 2006 to that of the QO line.

To Marc, I'll have to ask the rep for one of those see through jobs, looks pretty wicked.

 

[jim dungar]

Also, the reps stated that the internals changed in 2006 to that of the QO line.

I was told back in the late 80's that the internals were the same, although I don't remember if the original HOM line had their Qwick-Open characteristics.

 

[jdsmith]

I too think that is neat (a little shunt trip stuffed in ther - cute.) - as I am now 100% positive that they can reduce the cost per buy relocating all but the soloniod and the CT and have a single plug in unit to cover an entire panel. i.e. have a single more robust upgradable processor in the panel for sensing and triggering the trip mechanism. Hey at that point make a universal breaker - and have the processor gather information on the circuit and trip it if it goes outside of what it was programmed for... I'm calling it my dream panel...

Sounds similar to the 480v switchgear we've got on order (GE Entellisys.) There's still an electronic trip unit for each breaker, but the data from that set of CTs goes to a central computer for the switchgear lineup to reuse the CT readings for bus differential protection. The central computer can also reprogram all of the trip curves according to different profiles for normal operation, quick trip maintenance mode, and anything else we want. Supposedly we're going to have the largest installation so far so I'm sure we'll be a beta test site to some extent.