Cutting hole over knockouts?

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lakee911

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Columbus, OH
Is it permissible to cut a new hole (for conduit entry) in a panel if it already has factory provided knockouts? I'm assuming that it is if it is a blank space, but what if it isn't? Can they be cut partially over a factory knockout?
 
infinity

infinity

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We enlarge factory KO's all of the time. Typically when running conduit into a box or panel with factory KO's the KO's are never in the right place. For commercial work we try to always order the back box with no KO's at all or just on one end. Then we can flip the can over for use either with or without the KO's.
 
jaylectricity

jaylectricity

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Location
Massachusetts
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licensed journeyman electrician
The one problem I see is that when your hole overlaps factory-cut concentric knockouts. When you use the KOs as manufactured, your locknut does not cross and crimps or cuts.

Although many panels have 3/4"-2"KOs that aren't concentric, each circle meets at one side of the overall KO. So maybe there is no difference.
 
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lakee911

Senior Member
Location
Columbus, OH
TOOL_5150 said:
Occasionally, I just let it be, but if its really messed up, I just break it all out and screw a 4sq cover to the panel and punch the size hole I need.

~Matt
Click to expand...

I wondered how one would fix the 'mickey mouse problem' and that seems like it would certainly be one option, but how does that not constitute as modifying the panel? Wouldn't it violate the UL listing?

Thanks.
 
don_resqcapt19

don_resqcapt19

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Illinois
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retired electrician
lakee911 said:
I wondered how one would fix the 'mickey mouse problem' and that seems like it would certainly be one option, but how does that not constitute as modifying the panel? Wouldn't it violate the UL listing?

Thanks.
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I don't see the use of a blank cover or sheet steel to close an open hole any more of a modification than the use of a KO closer or reducing washers. You may have to bond around the blank cover as it has not been tested as part of the EGC path for that installation.
 
infinity

infinity

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e57 said:
The panel board is that thing inside the "enclosure"... ;)
Click to expand...

As E57 pointed out a "panel" is actually two parts as defined by the NEC. The panelboard, the part with the bus, breakers etc. And the cabinet which is the enclosure that holds the panelboard.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
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Henrico County, VA
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Electrical Contractor
480sparky said:
Personally, I think all tubs should come w/o KOs.
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I don't think never having KO's is any better than always having them. It should be based on each job.

I don't recall having a problem with factory KO's in residential installations. In fact, I plan around them.
 
e57

e57

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Location
San Francisco, CA
LarryFine said:
I don't think never having KO's is any better than always having them. It should be based on each job.

I don't recall having a problem with factory KO's in residential installations. In fact, I plan around them.
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If there were a standard layout that would survive every manufacturer and over decades I might agree. But in most retrofits if there is conduit - it's a problem. And in many situations for new construction, the holes are dictating what can come out and where - it should be the other way around... IMO if Joe Blow HO, or Jack Hack the rope-a-dope machine want to install panels they should invest in hole cutters... ;) :D (Larry - when I say this I do not mean you.) A carbide hole cutter takes only moments to punch the right size, quanity and placement of holes. While holes in panels may work sometimes they don't always do - and since supply houses only carry what they sell/make.... Maybe all panel manufacturers should move to provide both options - no holes on back and the side, and removable tops and bottoms that can bolt in. Have the ones with holes installed (Since those who use them apparently lack the tools of the trade...), and the ones without holes for those who need/use them hanging on the back. This way supply houses need not carry both, and in the load center & panel board market there would be a standard that served all. (rather than screwing 1/2 of us - all the time...)
 
e57

e57

Senior Member
Location
San Francisco, CA
LarryFine said:
Actually, I believe most major manufacturers do offer more than one pattern of KO's, as well as blank ends.
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No... Holes are enclosure based - this enclosure gets this pattern by this manufacturer, and different ones from the other one... NO HOLES - In bolt-on maybe? Special order in most cases... But definately not in the average BR type stab in load center...

I'm sure a number of us have seen them stupid LV panels with the bottom that has a 1G cut-in KO. I'm not sure which company - but one of them makes a plate with that in it that can be moved top to bottom with just 4 - 10/32's - like an insert. Thats what I'm thinking of... You want KO - just install it as is. You don't want KO's or the provided ones won't work for you - cut your on on the provided plate and drop it into place after removing what will be known as the hack plate...... ;)
 
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macmikeman

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Location
Planet macmikeman
e57 said:
No... Holes are enclosure based - this enclosure gets this pattern by this manufacturer, and different ones from the other one... NO HOLES - In bolt-on maybe? Special order in most cases... But definately not in the average BR type stab in load center...

I'm sure a number of us have seen them stupid LV panels with the bottom that has a 1G cut-in KO. I'm not sure which company - but one of them makes a plate with that in it that can be moved top to bottom with just 4 - 10/32's - like an insert. Thats what I'm thinking of... You want KO - just install it as is. You don't want KO's or the provided ones won't work for you - cut your on on the provided plate and drop it into place after removing what will be known as the hack plate...... ;)
Click to expand...

If I am understanding you correctly, the rectangular knock out plate in some LV cabinets for structured wire is meant to have a handy box with a receptacle screwed to the LV box for powering up coax amplifiers. Of course no LV contractor would ever think of trying to run power to his box all by himself without the help of a licensed electrician...
 
mivey

mivey

Senior Member
LarryFine said:
I don't think never having KO's is any better than always having them. It should be based on each job.

I don't recall having a problem with factory KO's in residential installations. In fact, I plan around them.
Click to expand...
I agree. Order with KO's for flexible conduit or cable; without for non-flexible conduit. Or something like that.
 
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