# can one breaker be tripped when another one trips with a mechanical short?



## lj150 (Oct 21, 2009)

can one breaker be tripped when another one trips with a mechanical short?
Details:

3 phase power common neutrals throughout system. 
one 20a breaker tripped because of broken cube-tap shorting hot to neutral and or ground at an outlet. 
The breaker would not re-set. 
The broken cube-tap was removed and the breaker was reset. 
The outlet tested hot. 
another outlet on the same breaker would not work after the shorting cube tap was removed and the breaker was re-set. No reason discovered yet. 

a second 20a breaker was tripped for no visible reason. 
No add'l equipment had been plugged in or changed. 
second breaker runs 2 computers and a printer, and has run the same stuff for years. 
Could the second breaker have been tripped by the short in the first because of a common neutral and (perhaps) some miswired outlet(s)?

I know both of the breakers tripped between 6 pm and 10:10 am. I believe the broken cube-tap was hit between 7am and 8:20 am. I have no way to know exactly when the breakers tripped. at 10:10am, they were both out.


----------



## 220/221 (Sep 25, 2007)

I have often seen a breaker trip when the one above/below it tripped on a hard short. I don't know what causes this but I do know it's common.

The recep on the circuit that faulted and will not come back on is another issue. There may have been a marginal connection (backstabbed recep, loose wirenut?) which burned open due to the large temporary current flow.


----------



## lj150 (Oct 21, 2009)

The breakers were not next to each other. They have the same feed and neutral buss. I do not think they were on the same phase. the first breaker was #40 in panel1a the second breaker was #41 in panel1b


----------



## lj150 (Oct 21, 2009)

I did recommend checking for a bad connection or burnt wire in the non working outlet or it's feed. I believe they opted to re-feed it as the walls were open at the time and it seemed less work.


----------



## user5941 (Mar 16, 2009)

220/221 said:


> I have often seen a breaker trip when the one above/below it tripped on a hard short. I don't know what causes this but I do know it's common.
> 
> .


 It's called heat. Breakers by design trip because of heat and that heat can be transfered to adjoining breakers.


----------



## william1978 (Sep 21, 2008)

What is a cube-tap?


----------



## brian john (Mar 11, 2007)

rewire said:


> It's called heat. Breakers by design trip because of heat and that heat can be transfered to adjoining breakers.


Breakers trip from long time operation due to heat, they trip on instantaneous operation due to a coil and magnetizing forces from the excessive current.

While there is heat generated in an instantaneous operation I doubt the heat from a 20 amp CB would be sufficient to trip another CB.

What is feasible is the mechanical latch is operated from an adjacent CB operating, seldom see a CB not adjacent to the tripped CB opening. But it is possible.

A fault on one circuit properly installed should NOT trip another CB with a circuit properly installed.

Did you meg the affected circuits, prior to closing the CB into a possible fault?


----------



## lj150 (Oct 21, 2009)

william1978 said:


> What is a cube-tap?


adapter to plug 3 things into one recepticle.


----------



## lj150 (Oct 21, 2009)

There could be reversed polarity in somewhere in the circuit (i've found that before)
what is meg


----------



## Mr Zappa (Oct 21, 2009)

lj150 said:


> There could be reversed polarity in somewhere in the circuit (i've found that before)
> what is meg


 i believe meg is short for megger bro. diggin the pensive vibe of this thread btw.... nice one fellas...mellow:thumbsup:


----------



## drsparky (Nov 13, 2008)

lj150 said:


> There could be *reversed polarity* in somewhere in the circuit (i've found that before)
> what is meg


????????:001_huh:


----------



## nutsla (Oct 21, 2009)

brian john said:


> Breakers trip from long time operation due to heat, they trip on instantaneous operation due to a coil and magnetizing forces from the excessive current.
> 
> While there is heat generated in an instantaneous operation I doubt the heat from a 20 amp CB would be sufficient to trip another CB.
> 
> ...


This is very sound knowledge indeed. Just as an after thought have you tonged the adjacent CB and checked its current/load?, it is possible that the adjacent CB is sitting near its limit, thus an instentanious short circuit trip in another CB nearby may have enough vibration and/or surge if on the same phase to trip this CB.


----------



## brian john (Mar 11, 2007)

nutsla said:


> . Just as an after thought have you tonged the adjacent CB and checked its current/load?, it is possible that the adjacent CB is sitting near its limit, thus an instentanious short circuit trip in another CB nearby may have enough vibration and/or surge if on the same phase to trip this CB.


 
*tonged*= measured the current utilizing an amp clamp, I would assume?

GOOD POINT.


----------



## brian john (Mar 11, 2007)

lj150 said:


> There could be reversed polarity in somewhere in the circuit (i've found that before)
> what is meg


 
Nope should have NO BEARING on the subject at hand.


http://www.biddlemegger.com/biddle/Stitch-new.pdf


----------



## nutsla (Oct 21, 2009)

brian john said:


> *tonged*= measured the current utilizing an amp clamp, I would assume?
> 
> GOOD POINT.


Sorry Brian, in the UK we just say tonged, I will try to be a bit more concise, by the way you write some good stuff buddy.


----------



## lj150 (Oct 21, 2009)

reversed polarity- the neutral and hot swapped at an outlet or fixture.


----------



## lj150 (Oct 21, 2009)

Meter comes this morning--only had wiggie yesterday.


----------



## Mr Zappa (Oct 21, 2009)

nutsla said:


> Sorry Brian, in the UK we just say tonged, I will try to be a bit more concise, by the way you write some good stuff buddy.


 pull YOUR tongue out nutsla....:laughing:just kidding buddy


----------



## user5941 (Mar 16, 2009)

nutsla said:


> Sorry Brian, in the UK we just say tonged, I will try to be a bit more concise, by the way you write some good stuff buddy.


 suck up :whistling2:


----------



## brian john (Mar 11, 2007)

lj150 said:


> reversed polarity- the neutral and hot swapped at an outlet or fixture.


 
Still will not result in a circuit breaker tripping.


----------



## brian john (Mar 11, 2007)

nutsla said:


> Sorry Brian, in the UK we just say tonged, I will try to be a bit more concise, by the way you write some good stuff buddy.


 
I am married to a Brit, and speak some English, but tonged went right by me for a second.


----------



## lj150 (Oct 21, 2009)

Still no reason why the second breaker tripped. Could be someone plugged in something they're not telling me about.... I've split the load on the second breaker and will have to wait and see what happens. Thanks for the help.


----------



## brian john (Mar 11, 2007)

lj150 said:


> Still no reason why the second breaker tripped. Could be someone plugged in something they're not telling me about.... I've split the load on the second breaker and will have to wait and see what happens. Thanks for the help.


There is always a reason this stuff we call electricity is not magic, you just have not located the issue.

1. Amp the circuit.
2. If you are really concerned test the CB
3. Megger the circuits involved.
4. Ask questions everyone will lie but it never hurts to ask.


----------

