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  #1  
Old 10/13/12, 9:50 AM
Bruce A. King's Avatar
Bruce A. King Bruce A. King is offline
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Default Cutler Hammer panel

This type of main Cutler Hamer panel has been used for the last 10 years or so around here.

I started wondering about the listing/rating of the short jumper strap that connects the right bus to the left bus. The long flat silver strap is not the one in question, its the short strap that you typically see used for panel bonding to the left of the green bonding screw.

In this case its used for neutral currents from the right bus and for panel bonding so the question is all about the neutral current application/rating.
I have seen these main panels with all of the neutrals on the right bus.
I posted these pictures from a panel that was not cluttered so everything was visible.

I could not find anything in their documents (quick look) that indicated this would be right or wrong. NEC 480.40 basically requires this strap to be rated for neutral current it seems.

I called Cutler Hammer and the person I talked to only had some canned answers so I emailed her the pictures. I did not get a response yet so I assume she is having others look at it.

Anyone ever look into this or a similar installation? (the neutrals sharing screws with grounds are not part of this discussion please)
Attached Thumbnails
cutler-hammer-panel-043.jpg   cutler-hammer-panel-041.jpg  



B.A. King Home Inspections, LLC
www.BAKingHomeInspections.com
Serving Charlotte NC area and Rock Hill SC areas.
CMI Certified Master Inspector and Independent
License NC2449 and SC1597
704 301-3207



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  #2  
Old 10/13/12, 10:15 AM
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Default Re: Cutler Hammer panel

If it's factory designed and installed according to it's instruction IMO it's within it's listing and code compliant. There are some other issues there however. Is there a main CB out of the photo at the bottom?
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  #3  
Old 10/13/12, 11:19 AM
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Bruce A. King Bruce A. King is offline
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Default Re: Cutler Hammer panel

Quote:
Originally Posted by Robert Meier View Post
If it's factory designed and installed according to it's instruction IMO it's within it's listing and code compliant. There are some other issues there however. Is there a main CB out of the photo at the bottom?

yes, the 2nd picture shows the corner of the 200A breaker


It looks like it was designed to have only grounds on the right bus.
I will stay on Cutler H and make sure they provide an answer.



B.A. King Home Inspections, LLC
www.BAKingHomeInspections.com
Serving Charlotte NC area and Rock Hill SC areas.
CMI Certified Master Inspector and Independent
License NC2449 and SC1597
704 301-3207



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- Albert Szent-Gyvrgyi, Nobel Prize for Medicine 1937
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Old 10/13/12, 11:48 PM
Jim Port Jim Port is offline
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Default Re: Cutler Hammer panel

I agree with Robert. i don't see the issue with using the factory supplied bond strap. It was good enough to get the panel a listing from a NRTL.
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  #5  
Old 10/14/12, 10:38 AM
Bruce A. King's Avatar
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Default Re: Cutler Hammer panel

Quote:
Originally Posted by Jim Port View Post
I agree with Robert. i don't see the issue with using the factory supplied bond strap. It was good enough to get the panel a listing from a NRTL.

Lets make sure you are commenting on the original post.....
You are saying this bonding strap is also rated/listed for all or some of the neutral current ?

I agree that the small strap at the left looks heavy enough but the screw/connections that are associated with it are the weak link.



B.A. King Home Inspections, LLC
www.BAKingHomeInspections.com
Serving Charlotte NC area and Rock Hill SC areas.
CMI Certified Master Inspector and Independent
License NC2449 and SC1597
704 301-3207



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  #6  
Old 10/14/12, 10:49 AM
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Default Re: Cutler Hammer panel

If that strap was properly designed, tested and installed correctly then I don't see a problem. I do agree that using that screw in the path of the neutral current seems like a poor design.
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  #7  
Old 10/18/12, 3:46 PM
Justin Shields Justin Shields is offline
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Default Re: Cutler Hammer panel

IMO the screw is providing a mechanical connection between the two metal plates.
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  #8  
Old 10/18/12, 7:15 PM
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Default Re: Cutler Hammer panel

Quote:
Originally Posted by bking View Post
yes, the 2nd picture shows the corner of the 200A breaker


It looks like it was designed to have only grounds on the right bus.
I will stay on Cutler H and make sure they provide an answer.

Was there any installation instructions listed on the name plate?

I am leaning toward what you already suspect, that is that the right bus is ONLY for connection of EGs. That would probably be detailed in the installation instructions for the panel, and depending on its age, might not even be readily available to the person you spoke to. Usually I just ask to speak to an applications engineer when I reach out to an OEM. If not, you will usually go through 2 or 3 layers of CSA's who have product knowledge, but not a deep enough technical understanding to provide any worthwhile help.

It is a very good find and question on your part. It is amazing how many issues are created when installers simply do not read instructions. Please keep us posted on what you find out.
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  #9  
Old 10/19/12, 9:38 AM
Bruce A. King's Avatar
Bruce A. King Bruce A. King is offline
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Default Re: Cutler Hammer panel

I got an email back fron CH in a few days, here is what it said:

"The bonding strap is rated to carry neutral currents. Please refer the attached for details."


I attached the PDF......
Attached Files
File Type: pdf Cutler Hammer Neutral Assembly Description.pdf (54.5 KB, 279 views)



B.A. King Home Inspections, LLC
www.BAKingHomeInspections.com
Serving Charlotte NC area and Rock Hill SC areas.
CMI Certified Master Inspector and Independent
License NC2449 and SC1597
704 301-3207



"Discovery consists in seeing what everyone else has seen and thinking what no one else has thought."
- Albert Szent-Gyvrgyi, Nobel Prize for Medicine 1937
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  #10  
Old 10/19/12, 5:31 PM
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William Blackmon William Blackmon is offline
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Default Re: Cutler Hammer panel

Thanks for the update Bruce. Even though it is apparently rated and listed for the purpose, I am still suspect of it. Neutral currents can be an issue all unto themselves due to harmonic currents. As more and more variable frequency inverters find their way into homes, the issue will be compounded. Something we have been experiencing for years in industry.
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  #11  
Old 10/19/12, 8:06 PM
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Default Re: Cutler Hammer panel

How can you have harmonic currents in a 1, 120/240 volt system?
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  #12  
Old 10/19/12, 11:49 PM
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Default Re: Cutler Hammer panel

How can you not have harmonic currents when the base frequency is altered and distorted by electronic switching?

Granted, residential systems typically have lower current loads that are subject to harmonics, but they are still present nonetheless. As more and more manufacturers seek increased energy efficiency, the use of inverters and/or electronic switching will only increase.
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