'Proof' that AFCI devices really locate arcs.

[don_resqcapt19]

...
I can not speak for other manufactures (if you know Im really curious ), but in Square D breakers 15, 20 and 30 amp all have the same magnetic trip:
...

How so?...the time trip curve is based on multiples of the breaker rating.

 

[peter d]

At times I seriously believe only electricians should be allowed to touch home wiring.

I vehemently disagree. People should be allowed to do whatever they want in their own homes.

I have done a lot of plumbing including installing laundry sinks, replaced faucets, replaced water heaters, installed outdoor faucets, set furnaces, run refrigerant lines, and lots of small repairs. Heck, I even rough plumbed a brand new house and almost completely replumbed an old house too. All this and I have never had a plumbing license for one second.

 

[ActionDave]

And a lot of guys who have done service work have seen things that are beyond awful and yet we have not lost the faith......

That's a whole lot of words. I read most of them. I agree.

 

[ActionDave]

I vehemently disagree. People should be allowed to do whatever they want in their own homes.

I have done a lot of plumbing including installing laundry sinks, replaced faucets, replaced water heaters, installed outdoor faucets, set furnaces, run refrigerant lines, and lots of small repairs. Heck, I even rough plumbed a brand new house and almost completely replumbed an old house too. All this and I have never had a plumbing license for one second.

The main reason I became an electrician instead of a plumber came from my experience remodelling my own house.

 

[mbrooke]

How so?...the time trip curve is based on multiples of the breaker rating.

Where does it say that? The lower portion of the time current curve seems to shift to the left as the current rating goes up, lowering the magnetic trip:


http://static.schneider-electric.us...it Breakers/QO-QOB Circuit Breakers/730-4.pdf

I vehemently disagree. People should be allowed to do whatever they want in their own homes.

I have done a lot of plumbing including installing laundry sinks, replaced faucets, replaced water heaters, installed outdoor faucets, set furnaces, run refrigerant lines, and lots of small repairs. Heck, I even rough plumbed a brand new house and almost completely replumbed an old house too. All this and I have never had a plumbing license for one second.

I would to if it really happened, but at times it does get to me especially when HIs miss it and someone elese has to put up with it. And we all know who benefits from every screw up. In the 2017 NEC its being said that 240 volt circuits will now need GFCIs, not just 120 volt circuits. Obviously handyman/DIYs are screwing those up. :happyno:

 

[ActionDave]

...I would to if it really happened, but at times it does get to me especially when HIs miss it and someone elese has to put up with it. And we all know who benefits from every screw up. In the 2017 NEC its being said that 240 volt circuits will now need GFCIs, not just 120 volt circuits. Obviously handyman/DIYs are screwing those up. :happyno:

It seems to me you need to move to Germany to have any hope of happiness.

 

[mbrooke]

It seems to me you need to move to Germany to have any hope of happiness.

Any place that doesn't require AFCIs Im in


Seriously, Im content here. If we could restore the NEC back to common sense rules then Id be happy.

 

[ActionDave]

Seriously, Im content here. If we could restore the NEC back to common sense rules then Id be happy.

I would be happy with that too, but I'm not willing to sacrifice the spirit of freedom we enjoy here in the US to achieve that. Yes, the NEC overreaches with every new code cycle, but that is not enough for me to sign on with the idea that only professionals are allowed to do electrical work, or plumbing work, or car mechanic work, or food preparation work, or weed killing work, or firewood chopping work, or deck construction work,......

 

[mbrooke]

I would be happy with that too, but I'm not willing to sacrifice the spirit of freedom we enjoy here in the US to achieve that. Yes, the NEC overreaches with every new code cycle, but that is not enough for me to sign on with the idea that only professionals are allowed to do electrical work, or plumbing work, or car mechanic work, or food preparation work, or weed killing work, or firewood chopping work, or deck construction work,......

I know, like I said if it ever came about (making DIY work illegal) Id probably complain. Does the thought cross my mind? Yes, but not enough to actually fight for it.

There is one place however where I believe only professionals should be allowed to touch and thats public pools and marinas.

 

[don_resqcapt19]

Where does it say that? The lower portion of the time current curve seems to shift to the left as the current rating goes up, lowering the magnetic trip: ...

You are correct that they are close to being the same for those 3 sizes. I did not look closely at the rating lines on the time trip curve.

225 amp at the low end of the range of the instantaneous trip for the 15 and 25 amp breakers and 250 for the 20 amp breaker, but it is a range and they might not trip until the high end which is 825 for the 15 amp, 900 for the 20 amp and 875 for the 25 amp. That was working off curve 730-4 which is the curve for 2 and 3 pole breakers and for the HM single pole breakers.

Curves 730-2 and -3 show a much lower instantaneous trip for the single pole 15 and 20 amp breakers as you said in a previous post. 105 amps for the 15 and 120 amps for the 20 amp.

 

[templdl]

Where does it say that? The lower portion of the time current curve seems to shift to the left as the current rating goes up, lowering the magnetic trip:

[o:

An interesting part of the TC I would like to know what their reasoning is behind the design. What came first, the chicken or the egg? I wonder if it was intentional as that family of breakers probably is manufactured with the exact same mag elements and the thermals calibrated for the rating. The present design may be incapable of a lower mag pickup value while being kept within a practical tolerance.
Another thought would be if the manufacturers shy away from àddressing a lower mag pick up because of their manufacturing limitations in producing these product in large quantities and the allowable pickup tolerances. Those mag elements I don't think are capable of being even being calibrated because of their simplistic design and not finding it to be a necessity.
Considering that the general consensus is the the AFCI is a bust if it was determined that focusing on the mag trip of these breakers would be beneficial it may lead to a mandate that the manufactures develop a product that has the capability to provide a lowered inst trip w/O nuisance tripping.
The manufactures appear to have recognized that a lowered inst pickup value is beneficial without even being forced to do so and not adding to their manufacturing costs. This may be their limitations.
If it was mandated that inst pickups would provide better protection that would cause them to redesign the mag element to meet the requirements. It woukd also be understood that in almost all likely hood would increase the cost of manufacturing the device.

 

[mbrooke]

You are correct that they are close to being the same for those 3 sizes. I did not look closely at the rating lines on the time trip curve.

225 amp at the low end of the range of the instantaneous trip for the 15 and 25 amp breakers and 250 for the 20 amp breaker, but it is a range and they might not trip until the high end which is 825 for the 15 amp, 900 for the 20 amp and 875 for the 25 amp. That was working off curve 730-4 which is the curve for 2 and 3 pole breakers and for the HM single pole breakers.

Curves 730-2 and -3 show a much lower instantaneous trip for the single pole 15 and 20 amp breakers as you said in a previous post. 105 amps for the 15 and 120 amps for the 20 amp.

Nahh, trust me it took me some time to see the graph shift. The magnetic trip does appear to stay similar over a broad range of breakers. The concept also holds true for breakers 30 to 125 amps, the magnetic trip is the same over about 4 or 5 different handle ratings. I will calc the others and post them. This left me scratching my head when it came to up-sizing breakers for motors, but I somehow have the feeling Square D is the only one doing it. All other trip curves Ive seen do indeed appear to be based on multiples of the handle rating, usually starting 10 for single poles.

In regard, that 105 amp value is the lowest of any single pole residential Ive seen.

An interesting part of the TC I would like to know what their reasoning is behind the design. What came first, the chicken or the egg?I wonder if it was intentional as that family of breakers probably is manufactured with the exact same mag elements and the thermals calibrated for the ratin

g.

I think thats what it might be. If you crack open a 15, 20 and 25 amp breaker the internals look exactly the same, ditto for 35 to 50amp breakers. Its possible the only change for them is via bi metal strip or its thermal trip calibrating.

FWIW, I see most breakers have one or two factory calibration screws that are cemented or papered over, is it possible these alone determine the trip rating? (ie tightened to X turns for 15 amps Y turns for 20? (see pic for example)

The present design may be incapable of a lower mag pickup value while being kept within a practical tolerance.
Another thought would be if the manufacturers shy away from àddressing a lower mag pick up because of their manufacturing limitations in producing these product in large quantities and the allowable pickup tolerances. Those mag elements I don't think are capable of being even being calibrated because of their simplistic design and not finding it to be a necessity.

I agree with you here, IMO with the present design manufacturing tolerance could produce magnetic trip values either higher or lower then intended. In theory the mag trip could be lowered by changing the tension of the spring at top, but something as simple as temperature could alter its tension.

Thus IMO a dedicated solenoid would be the best option. It can be built around tighter parameters, tighter curves and less variant to other factors.

Considering that the general consensus is the the AFCI is a bust if it was determined that focusing on the mag trip of these breakers would be beneficial it may lead to a mandate that the manufactures develop a product that has the capability to provide a lowered inst trip w/O nuisance tripping.
The manufactures appear to have recognized that a lowered inst pickup value is beneficial without even being forced to do so and not adding to their manufacturing costs. This may be their limitations.
If it was mandated that inst pickups would provide better protection that would cause them to redesign the mag element to meet the requirements. It woukd also be understood that in almost all likely hood would increase the cost of manufacturing the device.

I think everyone knows. ULs own reports advocate it and manufactures going through the effort to do so in the 90s leads me to believe there is serious reason.


I will go out on a limb having nothing solid to back this but IMHO manufacturers lowering the magnetic trip in residential breakers has been on of the biggest improvements in electrical safety, best part it didn't cost electricians anything nor nuisance tripping.

 

[templdl]

I will go out on a limb having nothing solid to back this but IMHO manufacturers lowering the magnetic trip in residential breakers has been on of the biggest improvements in electrical safety, best part it didn't cost electricians anything nor nuisance tripping.

I think that we are on the same page. I do think that the present design may have its limitations which may have been reached. The magnetic trip structure design may not have any additional capability that would allow it to be manufactured withing a given mag trip calibration window.
Thus the mag trip element design as it now exists may have to be redesigned but before this even happens as set of goals/requirements must be established that makes sense, that would be agreed upon that would add to circuit protection without nuisance tripping.
I too have taken breakers appart. I have a C-H BR breaker with a clear molded case so that you can see the working parts. I've taken apart molded case breakers all the 2000a as well as there interchangeable trip units. In doing so I was able to obtain a wealth of knowledge an appreciation about what makes them work.
When you see the internal parts of one of those load center breakers it is amaising that they are even capable of doing what they do.

 

[mbrooke]

I think that we are on the same page. I do think that the present design may have its limitations which may have been reached. The magnetic trip structure design may not have any additional capability that would allow it to be manufactured withing a given mag trip calibration window.
Thus the mag trip element design as it now exists may have to be redesigned but before this even happens as set of goals/requirements must be established that makes sense, that would be agreed upon that would add to circuit protection without nuisance tripping.
I too have taken breakers appart. I have a C-H BR breaker with a clear molded case so that you can see the working parts. I've taken apart molded case breakers all the 2000a as well as there interchangeable trip units. In doing so I was able to obtain a wealth of knowledge an appreciation about what makes them work.
When you see the internal parts of one of those load center breakers it is amaising that they are even capable of doing what they do.

I think another limitation behind lowering the magnetic trip thus far is application use. A single pole breaker can be found anywhere from low inrush applications like general use outlets to high in rush like Microwaves and garage power tools.

If we did go with the reduced magnetic trip route we would probably see 2 categories of breakers, the ones we have now (10x) for kitchens, garages, laundry, and a second kind with a 5 to 7x trip for bedrooms, hallways, living rooms and the like. And of course you have a 3rd category (High magnetic) which is typically not found in residential.

I would be very interested in seeing your BR plastic breaker, as well as learning how residential breakers operate. I greatly appreciate knowledge like that, especially now that AFCIs have me re-examining electrical theory.

 

[romex jockey]

A noble aspiration, yet if we did go with being empowered with engineering branch circutry , HD & Blowes would have to hire an entirely new contingent of 'on site trainers' , along with the NEC accepting a higher order Mbrook....



~RJ~

 

[templdl]

I think another limitation behind lowering the magnetic trip thus far is application use. A single pole breaker can be found anywhere from low inrush applications like general use outlets to high in rush like Microwaves and garage power tools.

If we did go with the reduced magnetic trip route we would probably see 2 categories of breakers, the ones we have now (10x) for kitchens, garages, laundry, and a second kind with a 5 to 7x trip for bedrooms, hallways, living rooms and the like. And of course you have a 3rd category (High magnetic) which is typically not found in residential.

I would be very interested in seeing your BR plastic breaker, as well as learning how residential breakers operate. I greatly appreciate knowledge like that, especially now that AFCIs have me re-examining electrical theory.

Mmmmm, seems that I do have a Westinghouse quicklag C which is the individually mounted cable in, cable out variety. I can !end it to you for yu to look at.
I've also milled out a portion of a 150a 3p series C breaker to expose both the thermal and magnetic element as will as a CV nm m 150a frame HMCP milling the side away jusdt enough such the you can see the actual solenoid structure and how it is adjusted.

I have always found this stuff to be amazing.

 

[mbrooke]

A noble aspiration, yet if we did go with being empowered with engineering branch circutry , HD & Blowes would have to hire an entirely new contingent of 'on site trainers' , along with the NEC accepting a higher order Mbrook....



~RJ~

I doubt we can change DIYs, but professionals certainly would know how to apply them correctly.

Mmmmm, seems that I do have a Westinghouse quicklag C which is the individually mounted cable in, cable out variety. I can !end it to you for yu to look at.
I've also milled out a portion of a 150a 3p series C breaker to expose both the thermal and magnetic element as will as a CV nm m 150a frame HMCP milling the side away jusdt enough such the you can see the actual solenoid structure and how it is adjusted.

I have always found this stuff to be amazing.

Id be interested

 

[templdl]

I doubt we can change DIYs, but professionals certainly would know how to apply them correctly.


Id be interested

Send me a PM with your address and I'll mail it to you. Please return it whenever you are finished evaluating it.
Dave

 

[mbrooke]

Send me a PM with your address and I'll mail it to you. Please return it whenever you are finished evaluating it.
Dave

I meant pics lol :thumbsup:

 

[templdl]

I meant pics lol :thumbsup:

It's alot more fun to have it in your hand to look at and to play with believe me. I'm glad to find someone who is as curious as I am to figure out how they work.
If I can find an extra copy of breaker basics I'll include it as my gift to you.