Load Center Bus Stab Ratings - Electrical - Page 2 - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 03-10-2008, 11:15 PM   #16
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 5,227
Rewards Points: 2,424
Default

Load Center bus stab ratings


I think I will inquire about what constitutes a bus stab and the interpretation of what ' per branch circuit bus stab refers to '. It is starting to look like this was nothing to really worry about as far as a limitation for a sub-feed breaker.

Advertisement

Stubbie is offline   Reply With Quote
Old 03-10-2008, 11:19 PM   #17
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Rewards Points: 500
Default

Load Center bus stab ratings


Try a 2 pole GFCI Sq D QO for a hot tub. My customer almost had a heart attack.
jrclen is offline   Reply With Quote
Old 03-10-2008, 11:24 PM   #18
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Rewards Points: 500
Default

Load Center bus stab ratings


Quote:
Originally Posted by Stubbie View Post
I think I will inquire about what constitutes a bus stab and the interpretation of what ' per branch circuit bus stab refers to '. It is starting to look like this was nothing to really worry about as far as a limitation for a sub-feed breaker.
Great. It would be nice to get an answer from a manufacturer if possible.
jrclen is offline   Reply With Quote
Old 03-11-2008, 01:40 AM   #19
" Euro " electrician
 
frenchelectrican's Avatar
 
Join Date: Apr 2006
Location: WI & France { in France for now }
Posts: 5,369
Rewards Points: 2,000
Default

Load Center bus stab ratings


Quote:
Originally Posted by jrclen View Post
Try a 2 pole GFCI Sq D QO for a hot tub. My customer almost had a heart attack.
yeah but my customer just cuss at me think i am full of BS i say no honesty in my heart i knew the 2 P GFCI's will really get ya hard.



Otherhand .,,

I did recall the ITE [ Seimens ] did have rating no more than 140 amp total on the bus tab basied on copper bussbar but alum verison knock it down to about 110 or so.

and i am not sure but been digging up my notes many years ago i have a meeting with the SqD company i think they are pretty much limited to either 120 or 140 on QO series but HOMELINE series i think about 110 or 120a the most.

few year back i did install a big ase 150 amp breaker on 400 amp panel it took 4 breaker space instead of normal 2 space and also they designed the houseing that the breaker itself it will prevent other breaker to be installed the same tabs at all [ they bumped out a bit.][ also if i recall the note say if other breaker on the same buss tab it will only max to 20 amp breakers on the same tab but i will dig up that info to verify it. if so i will update later]

Merci, Marc
frenchelectrican is offline   Reply With Quote
Old 03-11-2008, 10:20 AM   #20
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Rewards Points: 500
Default

Load Center bus stab ratings


You just jogged my memory Marc. I too installed a branch circuit breaker a while back which stuck out the opposite side so no breaker could be installed opposing it. I can't remember the brand but it was in an industrial location. I have seen large breakers which take up extra spaces to make more contacts with the bus also.

I also worked with 3 phase ITE bolt on type panels which were limited to 100 amp branch circuit breakers. But you could attach them back to back. I never read the label to see if it was OK to do that.
jrclen is offline   Reply With Quote
Old 03-11-2008, 09:18 PM   #21
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Rewards Points: 500
Default

Load Center bus stab ratings


Stubbie,
Mike Whitt, Code Guru, answered the question. He indicated the stab is the entire stab bar. So the ampacities of opposing breakers would be added up to comply with the manufacturers instructions.

Here is a link to the thread:

click here

Last edited by jrclen; 03-11-2008 at 09:21 PM.
jrclen is offline   Reply With Quote
Old 03-12-2008, 02:32 AM   #22
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 5,227
Rewards Points: 2,424
Default

Load Center bus stab ratings


Thanks for the link. Well I guess we learned something from all this but I tell ya I can't say as I have ever come across another tradesman that was up on this little technicality. I just struck me that with all the sub-panel threads we have here it would be something worth investigating. Mike is a pretty darn sharp fellow and I have learned a lot from reading his replies on other forums. I probably should buy him dinner (maybe Mcdonalds if he is lucky...) cause he has won several disagreements for me with other co-workers while I was still active at Ford. I must say I have enjoyed getting to the heart of the issue of this bus stab thing with you and Speedy.

Just so I get Mikes reply clear he is saying that if my bus stab is rated 70 amps and I place a 70 amp breaker on the stab then I am not allowed to place another breaker opposing it, is that the correct interpretation?
Stubbie is offline   Reply With Quote
Old 03-12-2008, 10:02 PM   #23
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Rewards Points: 500
Default

Load Center bus stab ratings


Quote:
Originally Posted by Stubbie View Post
Just so I get Mikes reply clear he is saying that if my bus stab is rated 70 amps and I place a 70 amp breaker on the stab then I am not allowed to place another breaker opposing it, is that the correct interpretation?
That is what Mike said. Petey also.

I've read panel labels to find interrupting capacity, and a few other issues, but not stab rating. After thinking back I do remember seeing maximum branch circuit size from time to time. But the stab rating is something I've managed to miss up to now.
jrclen is offline   Reply With Quote
Old 03-13-2008, 09:06 AM   #24
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 5,227
Rewards Points: 2,424
Default

Load Center bus stab ratings


Got it... Ok I've got a couple inquiries in to square d and eaton cutler hammer about this bus stab thing just so we can get their side of this issue. I'll paste their replies when I get them....and we can put this issue to rest until the next subpanel post......
Stubbie is offline   Reply With Quote
Old 03-13-2008, 10:56 AM   #25
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Rewards Points: 500
Default

Load Center bus stab ratings


Quote:
Originally Posted by Stubbie View Post
Got it... Ok I've got a couple inquiries in to square d and eaton cutler hammer about this bus stab thing just so we can get their side of this issue. I'll paste their replies when I get them....and we can put this issue to rest until the next subpanel post......
That would be great. And now days those panels are what I use most often so that'll work out great. You're right, this will do until the next time.
jrclen is offline   Reply With Quote
Old 03-13-2008, 04:40 PM   #26
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 5,227
Rewards Points: 2,424
Default

Load Center bus stab ratings


I heard back from square d today, which I have posted below. It would appear as we have already agreed that you need to check the panel specifications as it may or may not have a restriction. Mr. Snapp does give us the reason for the bus stab rating (when a panel is listed with one) being a heat rise issue in accordance with UL standards.


Most Square D QO or HOMELINE panels are supplied with "double row" bus
bar construction. This means that the bus bars will have branch circuit
breakers plugged onto the bus bars from the left and from the right.
The "bus stab", "bus finger" or even "connector finger" is the point on
the bus bar that the branch circuit breakers electrically connect to the
bus bar. For instance, a 40 space panel will have 20 "bus stabs". The
bus stabs accept circuit breakers from both sides, providing the
capability to plug on 40 1-pole circuit breakers.

If your panel is restricted to 125 ampere per bus stab, that means that
you cannot put two breakers onto that bus stab (one from each side)
that exceed 125 amperes between them. For instance, you could place two
60 ampere breakers (60A+60A=120A) across from one another on the same
bus stab(s), but you could not place two 70 ampere breakers
(70A+70A=140A) across from one another on the same bus stab(s).

This restriction is not applied to all QO or HOMELINE panels. The
restrictions are applied only when we must limit the total amperage on a
stab to pass applicable UL heat rise tests.

I hope that this has satisfactorily answered your questions. Please let
me know if you need anything further on this subject.

Regards,
Rick Snapp
Product Technical Support Group
Square D Company - Lexington Plant

Last edited by Stubbie; 03-13-2008 at 04:42 PM.
Stubbie is offline   Reply With Quote
Old 03-13-2008, 06:26 PM   #27
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Rewards Points: 500
Default

Load Center bus stab ratings


Quote:
Originally Posted by Stubbie View Post
I heard back from square d today, which I have posted below.
Perfect. That spells it right out. And as you say, we are going to need to read the label to comply. Thanks for your efforts. I'm going to copy that explanation for future reference.

Advertisement

jrclen is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Moved ceiling light in bedroom to center, now trips breaker blthomas Electrical 18 01-24-2008 05:29 PM
framing, expanding wall opening wall - load bearing? nave Remodeling 5 01-23-2008 04:44 PM
% total roof load on interior bearing wall? Grommet Building & Construction 1 03-29-2007 08:37 AM
Load Center dwayne Electrical 4 07-09-2006 02:02 PM
100A load center run Littlefatdog Electrical 12 06-15-2006 03:31 AM




Top of Page | View New Posts