Problem with MS breaker terminals clamping / holding wires

[Nashville]

After 3 years of anticipation of going live, I'm having issues in the oddest of situations. I am wiring up 2 alum. E boxes. The breaker terminals don't seem to bite on the wires hard enough to hold them. They keep coming out and its driving me crazy.

Any thoughts? Anyone else had this problem? I'm using 8 gauge stranded copper.

[Westbranch]

what did you torque them to?  You should re-tighten them after a couple of hrs. as copper 'flows' under pressure.

[Vic]

Hi Nashville,

You did not state the type of Breaker that is giving the problems.
,  butl

I have had significant issues with the MN/CBI AC DIN Rail breakers NOT applying enough force to ensure that the wires simply do not fall out of the contact "shoe".  It seems that the passage for the wire is BLIND (you cannot see this passage in most situations where the breaker is mounted in a box,  AND the screw that applies the force onto the shoe seems too small diameter,  such that it is almost impossible to apply the required torque.

I hate to say that I prefer the SquareD QOU breakers,  with their external,  visible, front-facing  large screws that apply the clamping force to the wire.   It is possible that the QOUs are being discontinued -- they have become more difficult to find,  here in the USA,  in my experience.

This may not be the issue that you are having,   but,   was a bit surprised that this condition existed on the 30 Amp MN,  CBI0-manufactured Din-rail breakers.   ...  thought that I was the only one.   Just my experience.
Vic

[Nashville]

Hi Nashville,

You did not state the type of Breaker that is giving the problems.
,  butl

I have had significant issues with the MN/CBI AC DIN Rail breakers NOT applying enough force to ensure that the wires simply do not fall out of the contact "shoe".  It seems that the passage for the wire is BLIND (you cannot see this passage in most situations where the breaker is mounted in a box,  AND the screw that applies the force onto the shoe seems too small diameter,  such that it is almost impossible to apply the required torque.

I hate to say that I prefer the SquareD QOU breakers,  with their external,  visible, front-facing  large screws that apply the clamping force to the wire.   It is possible that the QOUs are being discontinued -- they have become more difficult to find,  here in the USA,  in my experience.

This may not be the issue that you are having,   but,   was a bit surprised that this condition existed on the 30 Amp MN,  CBI0-manufactured Din-rail breakers.   ...  thought that I was the only one.   Just my experience.
Vic

This is exactly the problem that I am having. I guess I will have to switch to Square D too. My breakers are the gray ones QZD DIN. Major disappointment when I am so close to being done. I wonder if a hex screw would help apply more torque. Can you get the Square D's at Lowes or is this a specialty product?

[Nashville]

what did you torque them to?  You should re-tighten them after a couple of hrs. as copper 'flows' under pressure.

Yes I am familiar with flows. I can't get anywhere near the torque spec.

[Halfcrazy]

The CBI breakers can be a little different. I find if I untwist the wire so the strands are all straight and then torque the breaker and wait an hour and re-torque I have 0 issues. Before I used to untwist the wire I used to have the same similar issue.

I will say CBI has redesigned the clamp as well as the screw and the newer ones are better at gripping.

Ryan

[Vic]

Thanks Ryan for the added info.

Believe that had not ever twisted the stripped wire,  but cannot actually remember at this time.  Great news that CBI has a new design ...  had gone to using a serious amount of PULL on the wire Pull-Test,  which helped,  but there were a surprising number of failures on this pull test.

Nashville,  NO,  would be surprised if you could find ANY QOU breakers at ANY local source,  even  Wholesale Electrical supply houses may well not have access to these.  This is really a specialty breaker,  more of an Industrial item.   With diligent effort,  the older design can be made to work.  Just do a pull of a few pounds on each wire on each of these breakers,  after re-torqueing all of the wire's screws.  This has worked here,  but making sure that the wire is actually seated into the correct part of the clamp has been the most difficult thing for me,  as one almost needs to do this guiding and tightening of the screws BEFORE these breakers are mounted.  This way,  one can actually (kind of) SEE where the wire needs to go,  and if it has gone there before tightening/torqueing the screws,  IMHO.

Did look at several Solar Resellers just now,  and no real inventory.  WW Grainger lists some,  but as is Grainger's style,  they seem HORRIBLY expensive.

Do not know is there is a new part number for the MN/CBI redesigned breakers,  or if the case is now black instead of grey ...  hope that there is a way of knowing before purchase if one is buying new or not so new stock (? ...  and so on.   Good Luck.  Not to rag on MN/CBI too much.     Vic.

[Nashville]

The CBI breakers can be a little different. I find if I untwist the wire so the strands are all straight and then torque the breaker and wait an hour and re-torque I have 0 issues. Before I used to untwist the wire I used to have the same similar issue.

I will say CBI has redesigned the clamp as well as the screw and the newer ones are better at gripping.

Ryan

Can I exchange ? Oh please please please. .. I hate these : )

[Nashville]

Thanks Ryan for the added info.

Believe that had not ever twisted the stripped wire,  but cannot actually remember at this time.  Great news that CBI has a new design ...  had gone to using a serious amount of PULL on the wire Pull-Test,  which helped,  but there were a surprising number of failures on this pull test.

Nashville,  NO,  would be surprised if you could find ANY QOU breakers at ANY local source,  even  Wholesale Electrical supply houses may well not have access to these.  This is really a specialty breaker,  more of an Industrial item.   With diligent effort,  the older design can be made to work.  Just do a pull of a few pounds on each wire on each of these breakers,  after re-torqueing all of the wire's screws.  This has worked here,  but making sure that the wire is actually seated into the correct part of the clamp has been the most difficult thing for me,  as one almost needs to do this guiding and tightening of the screws BEFORE these breakers are mounted.  This way,  one can actually (kind of) SEE where the wire needs to go,  and if it has gone there before tightening/torqueing the screws,  IMHO.

Did look at several Solar Resellers just now,  and no real inventory.  WW Grainger lists some,  but as is Grainger's style,  they seem HORRIBLY expensive.

Do not know is there is a new part number for the MN/CBI redesigned breakers,  or if the case is now black instead of grey ...  hope that there is a way of knowing before purchase if one is buying new or not so new stock (? ...  and so on.   Good Luck.  Not to rag on MN/CBI too much.     Vic.

Thanks Vic. Your thorough replies are very much appreciated. Grainger is German for "you're gonna pay full retail for this buddy".  Although their service is second to none.

[Halfcrazy]

Thanks Ryan for the added info.

Believe that had not ever twisted the stripped wire,  but cannot actually remember at this time. 

THHN comes pre-twisted. That's what got me, Just takes a slight turn the opposite way with your linesman's pliers.

[Vic]

HC,  YES,  OK  now realize just what you were saying.  Thanks.

And,  is there a way of differentiating the latest MN Din AC breakers from the previous models without the better clamping scheme?

Do the old ones have the Grey plastic bodies,  and the new ones ALWAYS have the Black bodies.  Is there a new part number (guess that I could have tried looking but am not at the correct site to check) ?

Thanks,    Vic

[Halfcrazy]

No the new vs old style will be subtle. CBI will be sending them as inventory of the old ones dries up. The part numbers and everything are identical just a small design change.

Ryan

[Vic]

Thanks again Ryan.   CBI generally seems to do a good job,  and the MidNite  offerings are very,  very  cost-effective.  Think that you folks may have killed the SQ-D QOU line -- very hard to find,  especially in 60 A Duals.   73  Thanks,  Vic