Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
Came across this in my disconnect switch sppec section. So obviously that would mean the enclosure more than likely would have a female threaded hub?
Enclosure Question
- Thread starter Alwayslearningelec
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Sounds like threaded hubs but are you using many of the Type 4, 4X, and 12 enclosures.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
This is only a part of a spec. I do not know what the NEMA 250 means.
They want you to order enclosures without factory knockouts. There is nothing in that spec preventing you from making holes for conduit entrances in the field unless the enclosure is a type 7 or 9. There is nothing that requires you to use hubs unless they are needed to maintain the Type rating.
This is a pretty useless spec as Type 12 enclosure are the only ones, in this list, that are available with factory knockouts.
- Location
- Illinois
- Occupation
- retired electrician
That is the ANSI standard for enclosure types. However the certification to the NEMA standard is a self certification, like with a CE certification. If the product is required to be listed it would have to be certified by a NRTL.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
As a practical matter you can cut knockouts in normal enclosures, but explosion proof enclosures have to be drilled and tapped and it is not something you want to do in the field.
- Location
- Illinois
- Occupation
- retired electrician
We typically sent them out to a machine shop to be drilled and tapped, but you have to look at the instructions as they tell you the sizes and locations where you can tap an explosionproof enclosure. That is the cases were we could not get one with factory holes to match our installation. The best it to use one with factory holes even if you have to close any extra holes with explosionproof plugs.
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
Yes just about all the panels and disconnects are nema 4X. Why?
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
What is drill and tap exactly?
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
Thanks. You wouldn't tap a standard steel enclosure correct? Would imagine you need some thickness.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Explosion proof enclosures are typically quite thick 3/8 inch or maybe half inch. The conduit fittings actually screw into threaded holes made in the walls of the XP enclosure. XP pushbuttons and lights screw into drilled and tapped holes too.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
The theoretical minimal thickness is 1/16", of which a 10-32 screw just engages two full threads.
Most holes for screws in enclosures are punched rather than drilled, which thickens the metal.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
A lot of enclosures have tapped holes in them. Panel boards have tapped holes for ground bars and the bonding jumper between the neutral bus and the panel steel. Along with all the mounting holes.
Most control enclosures have drilled and tapped holes in the sun panel for a bonding wire.
They are fine thread so even with 16 gauge sheet metal it is two full threads because the holes are punched and the threaded area is made thicker.
This is why you have to use fine threaded fasteners for certain things.
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
So back to my original question. The panels and gear are NOT to have ko's. Agree? So then it would have to be a threaded hub. Agree?
Seems awfully unusual to have all the panels etc. have a threaded hub instead of ko.
Seems awfully unusual to have all the panels etc. have a threaded hub instead of ko.
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
Sorry it's only in the enclosed switches spec section. So pertains to disconnect switches only.
- Location
- Illinois
- Occupation
- retired electrician
Assuming that the enclosures are not explosionproof, you simply drill or punch your own holes in the enclosure. I always specified no factory knockouts as that makes it easier to layout the conduit.
Also applies to panelboards, gutters, & screw cover cans, also just makes the job easier.
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
Drill then tap for a threaded opening your saying? So it would be a female internal threded hole so to speak?
- Location
- Illinois
- Occupation
- retired electrician
No tap..just round hole made with a hole saw or a knock out punch. The conduit would install with two locknuts and a bushing in interior dry location.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
The spec is about purchasing enclosures without knockouts. Factory knockouts have been known to leak, be pushed out with finger pressure, and often are not in ideal locations based on planned conduit runs.
It says absolutely nothing about how entries are made in the field.
You are over thinking this. If still in doubt ask for a clarification/RFI.
It says absolutely nothing about how entries are made in the field.
You are over thinking this. If still in doubt ask for a clarification/RFI.
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