Panel ran in Series

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brother

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I ran into an installation where there were two 225 amp panels side by side. Conduit ran in between them. Apparently the the main breaker for panel 'A" is a 225 amp breaker that powers the buss of panel 'A" . Well the problem i have with this is that panel 'B" is fed off of panel 'A"'s buss, NO BREAKER . Basically they are in series, in order to work on panel "B" you have to turn off panel "A" 's main breaker, so all the circuits in BOTH panels are dead.

I cant think of the code article right off the top of my head but i think 408 comes into play of this being a violation, they (Panel B feeders') need to be on a main breaker and not just tied into the buss. Am i right???
 
Not a violation, what you describe we usually call a "double tub" panel and we sometimes do triple tub panels.

If they are supplied with a feeder then no main at all will be installed, if they are supplied directly from a transformer secondary they they will have a single main on the lead panel.

With a double tub we would have circuits 1 to 84 and a triple tub would have circuits 1 to 126.

In office buildings this becomes necessary for the large number of lightly loaded receptacle circuits.
 
iwire said:
Not a violation, what you describe we usually call a "double tub" panel and we sometimes do triple tub panels.

If they are supplied with a feeder then no main at all will be installed, if they are supplied directly from a transformer secondary they they will have a single main on the lead panel.

With a double tub we would have circuits 1 to 84 and a triple tub would have circuits 1 to 126.

In office buildings this becomes necessary for the large number of lightly loaded receptacle circuits.
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Ok, well maybe the numbering of the circuits. in both panels they just number from 1 to 42. its not a 2 part like you say. ;)
 
Also utilized for risers we have as many as 12 floors with feed through lugs, some are rated 225 amp some are 400 amp.
 
brother said:
Ok, well maybe the numbering of the circuits. in both panels they just number from 1 to 42. its not a 2 part like you say. ;)
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They do make 1-126 numbers for these triple wides.
 
brother said:
Also, i just HATE having to shut off 2 panels just to do work on the one. It just seems to me that it would make more sense to have a main breaker even with the higher numbering. Would it really be that much more expensive to have a main breaker to feed the next panel??
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Nothing in 3 phase is ever cheap.This is simply a design issue.If your paying then sure add a breaker.
 
Even if panel "B" had a main breaker you'd still end up shutting off both panels half the time since "A" feeds "B".
 
I've seen many of these double and triple panel setups where they butt them tight together side by side, cut out most of the sides of the panels, and put QuickEdge on the opening. I've always wondered if that squares with the code.
 
mdshunk said:
I've seen many of these double and triple panel setups where they butt them tight together side by side
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How do the covers fit? I'm guessing they don't hang over the side. (I don't work on the large panelboards nearly enough to remember.)
 
mdshunk said:
I've always wondered if that squares with the code.
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I bet it does, but i would'nt put my name on the install. 2 4" nipples would cover the feeders and the booboo branch circuits.
 
peter d said:
How do the covers fit? I'm guessing they don't hang over the side. (I don't work on the large panelboards nearly enough to remember.)
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If the cover part number ends in an "F" it will hang over, and if it ends in an "S" it will not. One of my pet peeves is people who use the flush cover on surface mounted panels. On some brands, like HOM, you don't even have that option, which is one reason I don't like them.
 
mdshunk said:
One of my pet peeves is people who use the flush cover on surface mounted panels.
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That's like using wall plates on handy boxes. Handy-box plates are bad enough.
 
LarryFine said:
That's like using wall plates on handy boxes. Handy-box plates are bad enough.
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Oh, yeah. Another one of my pet peeves. There's actually a NECA spec that prohibits wall plates on surface mounted boxes.
 
Also, i just HATE having to shut off 2 panels just to do work on the one
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1. How often in a commercial building are you allowed to shut off any panel during normal business hours?
2. If you are doing the work in off hours what does it matter if you shut of 1, 2 or 3 panels.
3. The added hassle of shutting off 2 or more panels is seldom justified by the added cost of a main CB in each panel.
4. There are some bad designs where disconnecting power is inconvenient but I do not think this falls into that category.
 
brian john said:
1. How often in a commercial building are you allowed to shut off any panel during normal business hours?.
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Not that offten, but sometimes we do. Ive done work in hospitals and even in that enviroment, we try not to work hot unless its really necessary (infesabile (sp?) as osha would say).

brian john said:
2. If you are doing the work in off hours what does it matter if you shut of 1, 2 or 3 panels..
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Yes it does matter actually, in the hospital, even though these arent emergency panels, when you have to shut down 2 panels because the other just didnt have a 'main' breaker feeding it just to do work on that 1 panel can be more of an unecessary disruption in my opinion.

brian john said:
3. The added hassle of shutting off 2 or more panels is seldom justified by the added cost of a main CB in each panel...
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Im at a lost on this statement, In the areas i work, haveing a main breaker to just isolate the 1 panel would save alot of time and money in staff preparation/work when working on these panels, since only one has to be down

brian john said:
4. There are some bad designs where disconnecting power is inconvenient but I do not think this falls into that category.
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Like i said, in the jobs ive been in/on this would always be inconveient, and sometimes 'infessiable' (sp?).
 
I'm not really up to speed 100% on NFPA 70E yet but if you just turn off the main breaker in the panel, aren't you still working "Near" live parts? The conductors feeding the main will still be hot. Wouldn't you still need to have all of the appropriate Live Work permits, hazard analysis, and PPE? If you shut off the feed ahead of these double or triple tubs, there would be no live parts in the panel and you would still turn off 2 or 3 panels.

I agree with Cow, you would still be shutting off both panels half of the time with a main for each tub.
 
brother said:
Im at a lost on this statement, In the areas i work, having a main breaker to just isolate the 1 panel would save a lot of time and money in staff preparation/work when working on these panels, since only one has to be down
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If you shut off the main in a typical panel IMO all the hot work rules still apply. Unless the panel is unusual and has the line side entirely guarded.


Bottom line it is not a safety issue, it is a design decision made by people who's job is often to bring the cost of the job down.
 
iwire said:
If you shut off the main in a typical panel IMO all the hot work rules still apply. Unless the panel is unusual and has the line side entirely guarded.


Bottom line it is not a safety issue, it is a design decision made by people who's job is often to bring the cost of the job down.
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Maybe i miss used the word 'main' in this context. Im talking about a breaker in panel 'A" that would feed panel 'B" i suppose is a more a 'feeder breaker'. If you just shut off the Feeder breaker in "A" then "B" would be completely dead and A would stay on, less disruption of power.

With B being tied to the buss like that, you have to turn off the 'main' in A just to kill B, thats just a bad design in my opinion.
 
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