Why the breaker trips

[kwired]

Will a standard clamp-on multimeter work to see a short? Like you'd see the buildup of amps before the breaker trips? I have never tried this.

Short circuit and ground faults generally are pretty rapid rise in current and unless there is too high of supply circuit impedance to limit the amount of current the OCPD often trips faster than many meters would be able to accurately display that current, though some might have a capture feature to show what the peak might have been after the fact. Even an analog meter you might see rapid rise but chances are that needle never reaches the actual peak before the OCPD opens the circuit as it would be too slow of a mechanical response to be able to do so.

 

[tortuga]

My diagnostic breaker for the mystery 'it trips randomly' is a 30ma GFPE breaker.
If I cant reproduce the problem while i am there I'll leave one of those and see if that trips.

 

[ptonsparky]

Sometimes you can hear the breaker trying to come out of the panel or feel it in your fingers as you switch it back on. Don't do it very often. Sometimes they quit tripping or do come out.
Spend the money get a decent meter(s). Learn how to use them. You need the tools to become proficient.

 

[jim dungar]

Like you'd see the buildup of amps before the breaker trips?

A short circuit gets to maximum value immediately, there is no build up.
Very few hand held meters can measure these currents. But, a meter with a Max Hold feature might capture a value well in excess of a full load (like motor inrush) which would indicate a potential problem.

 

[JoeNorm]

The reason I posted this is because I was brought out to job where the customer had a sporadically(but getting worse and worse over time) tripping Arc-fault breaker. It was a recently built, very high-end home. In that scenario I would have almost bet money that it was a faulty breaker, so I bought one to bring out and swap right off the bat. I did so but even the new one tripped. So then started the actual troubleshoot.

It took me a few hours but I was able to isolate it to one run of in-wall wiring that had somehow shorted. I disconnected that portion of wire from the circuit and all is well. I was happy to have found the problem but am always wondering how I could do it a little faster next time.

 

[hillbilly1]

A short neutral to ground will also trip them. Divide and conquer. Break the circuit in half, and go from there. Intermittent problems are the worst. Sometimes you can beat on the walls along the affected area to narrow it down.

 

[Little Bill]

A short neutral to ground will also trip them.

Not if it is the brand of AFCI that have taken the GF portion out.

 

[hillbilly1]

Not if it is the brand of AFCI that have taken the GF portion out.

Yeah, and that was really the only part that actually worked correctly.

 

[ptonsparky]

Yeah, and that was really the only part that actually worked correctly.

At least predictably.

 

[tortuga]

Yeah, and that was really the only part that actually worked correctly.

The 30ma GF portion of a AFCI is the most effective part as the whole idea of 120V drawing an arc is highly questionable,
I'd say a 30ma GF breaker is a suitable substitute for a AFCI where AFCI's are nuisance tripping.

 

[ptonsparky]

Not that much difference in price.

 

[Jraef]

never seen that type of seimens before either qp or the bolt on

Siemens sells a "Classified" version of their breakers, The QD series, designed for QO panels. Those have been available for over 30 years, but it's a well kept secret. They do NOT however offer an AFCI, GFCI or DF version for the QO panels, just 15-60A 1 and 2 pole standard breakers, so I'm not sure how useful they are now except for replacements.

Classified breakers means they are tested and listed by UL to be used in retrofitting into SPECIFIC panels made by other manufacturers. But because a PANEL is only listed with their same breakers, you technically cannot install a NEW panel with ONLY Classified breakers in it because you have not "followed the manufacturer's instructions" for the PANEL. But once a panel is installed and passed inspection, when you come in later and install a Classified breaker, it's code acceptable.

 

[hbiss]

Siemens sells a "Classified" version of their breakers, The QD series, designed for QO panels.

Why would you use those Siemens breakers instead of readily available QO breakers?

-Hal

 

[ptonsparky]

Why would you use those Siemens breakers instead of readily available QO breakers?

-Hal

Dang good question.

 

[Master Nater]

Why would you use those Siemens breakers instead of readily available QO breakers?

-Hal

why would square d make a homeline series breaker and panels (siemen's - like) instead of just selling their own QO?

i would ask the the same question for cutler hammer and their BR series...

 

[jim dungar]

why would square d make a homeline series breaker and panels (siemen's - like) instead of just selling their own QO?

Because, back in the 80's they wanted a cheaper product line so they could maintain the higher pricing on their QO line. Even today the QO is a broader offering than Homeline.

When it was introduced, Homline was only available in the large new housing markets like Florida and Arizona.

 

[curt swartz]

Because, back in the 80's they wanted a cheaper product line so they could maintain the higher pricing on their QO line. Even today the QO is a broader offering than Homeline.

When it was introduced, Homline was only available in the large new housing markets like Florida and Arizona.

I was one of the test contractors for the HOM products in the SF bay area. At the time I was doing a decent volume with the local Graybar branch. My sales person and the branch manager at the time were big Square D Geeks. They told me the HOM line was being introduced so Square D could compete with the others in the residential market while keeping the QO pricing higher.

 

[Jraef]

Why would you use those Siemens breakers instead of readily available QO breakers?

-Hal

Simple: so that Siemens and Murray distributors had something to sell to Square D users… in some small towns where there was only one wholesale house, that could be the difference between finishing a project today, or driving any hour each way to the next distributor and having to come back to finish a job another day. Not as much of an issue now, but it was 30 years ago.

By the way, Eaton sells a QO Classified breaker too. Probably for the same reason.

 

[Master Nater]

Because, back in the 80's they wanted a cheaper product line so they could maintain the higher pricing on their QO line. Even today the QO is a broader offering than Homeline.

When it was introduced, Homline was only available in the large new housing markets like Florida and Arizona.

my question was in response to Mr. Biss's question as to why anyone would want to buy a siemens breaker that is "classified" to fit in a QO panel.

TBH, your answer does not explain why they made it JUST LIKE the ITE/siemens/murray/everything else ... and why didn't they just make a QO-style panel, in aluminum bussing. it's the same answer. they were jumping on the bandwagon that siemens owned the rights to.

 

[jim dungar]

my question was in response to Mr. Biss's question as to why anyone would want to buy a siemens breaker that is "classified" to fit in a QO panel.

TBH, your answer does not explain why they made it JUST LIKE the ITE/siemens/murray/everything else ... and why didn't they just make a QO-style panel, in aluminum bussing. it's the same answer. they were jumping on the bandwagon that siemens owned the rights to.

They did make QO with aluminum bus. I believe they still do in smallest sizes.

I would have to look at the timing, but I believe the newer Seimens generation was introduced around the time that Homeline was. I want to say the intent was Homeline would become the residential line and QO would remain commercial and 3-phase, but the industry did not let that happen. Even 15 years ago very few supply houses, in this area, carried any Homeline at all. They let the big box stores deal with it.