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Joined: Jul 2001
Posts: 599
JBD Offline
I have noted most people talk about using bolt-on breakers with panelboards versus plug-on ones with loadcenters. Simply asking for a panelboard design does not guarantee bolt-on breakers. If you want bolt-on you must specify it,

My experience with Cutler Hammer CH and Square D QO breakers has been far fewer failures do to plug-on connections than with loose/stripped/cross-threaded connections when using bolt-on breakers.

I trust a factory built plug-on jaw more than an incorrectly field installed screw connection. But I do understand the concerns with the reinstallation of breakers and with "cheap" designs (i.e. FPE) especially on some aluminum bussing (i.e. Zinsco).

Joined: Apr 2001
Posts: 507
"My experience with Cutler Hammer CH and Square D QO breakers has been far fewer failures do to plug-on connections than with loose/stripped/cross-threaded connections when using bolt-on breakers."

My experience is exactly the opposite! I've seen many plug-on breakers that have burned the breaker and buss bar beyond use. But I've never seen a bolt on fail.

If the bolt-ons are loose or stripped that sounds like a workmanship issue. Bolt-ons are definitely not as "user friendly", but that really shouldn't be an issue for a pro.

Joined: Dec 2000
Posts: 4,289
I'm with the Golf Junkie.
I've had very few failures with bolt on C/B's, and lots with plug-ins, except JBD's favorite - QOs (JBD, I love SqD stuff) The bolt on failures have been poorly installed, either loose or cross-threaded so as to seem as if they're torqued down, even though the connection is still loose.
It hasn't been limited to field installed breakers.
Try taking a torque driver to a factory assembled panelboard sometime. (well, everytime, actually) You might by pleased, or maybe disgusted. Don't trust 'em.

I think Caselec's got the best option, if you can hold out for the leadtime go for the factory assembled version>

Joined: Oct 2000
Posts: 2,722
Broom Pusher and
I was once asked by a Foreman:
"What's The Difference Between A Load Center And A Panelboard?"
(BTW, the "Question" was posed in a "Loaded Question" format - I.E. the Foreman already had an answer, but it did not match mine...).

The only thing I could think of was the Depth / Width dimensions of the Can (Enclosure).

Figuring I must have come close to a satisfactory answer, along with not being aware of the "Loaded Question" scenario (until my response was ... "De-Bunked"...), my jaw dropped rapidly to the floor upon the resultant corrections applied with the Foreman's rebuttal of:

"No!!! The Difference Is Load Centers Use Plug-On Breakers, And Panelboards Use Bolt-On Breakers".

Being the Glutten for punishment that I am, what do I do now???... of course - point out the "Semi-Obvious" information:
[Linked Image]

  • NEC has no definition or constraints towards the term Load Center, but the term Panelboard is vastly used,
  • Most Catalogs describe Equipment of 225 Amps and less, at 250 VAC maximum; which reside within Metallic Enclosures having dimensions that allow for flush mounting in the typical 2" x 4" @ 14.5" finished Wall Cavity, as a Load Center, whereas Panelboards typically have 20" wide x 5.75" deep Enclosures,

And the biggest "Clinchers" of them all:


[*] Most Load Centers may be ordered with either option for OCPD Terminal Mounting scheme: Bolt-On Bus or a Plug-On Bus,

[*] Square D Bus Kits are optional both ways - either use QO Plug-On Breakers, or remove the "Plug-On Stabs" from the Bussing and install QOB Bolt-On Breakers - commonplace for Panelboards and Load Centers.

Without going into full details, as to the reply from said Foreperson in rebuttal to the items above, let's just say I found out three things about myself which I did not know until that day:


[*] I know nothing about Electrical Systems, Systems Designs, Materials, Manufacturers Data, or anything related to the "Commonly Known Stuff That All Electricians Know",

[*] The fact that I was unaware of Panelboards vs. Load Centers means I will NEVER be any good as an Electrician - and impossible to even think of shooting towards being an Engineer,

[*] I am the least knowledgable Person in the Trade, have no NEC knowledge, never specified or even ordered Equipment, and I am the laughing stock on the job because of this.

This excitement took place exactly One Year and Two Months ago from this very Day, on a Public Works project which I was pulling a "Triple Threat" type working deal on
(Project Manager, Journeyman Installer, Revised installs FWO plans drawing / engineering / submission - shop drawings + record drawings... all at the same time).

Sorry to vent this here, and as you can see I still have issues over this.

Anyhow, AFAIK, the only difference between them is what you call them - Load Centers or Panelboards.
I prefer "Panelboards" and use the term as default to describe any OCPD assembledge cabinets that do not "Qualify To Be Defined As Switchgear", and contains MCCBs - but not Fuses or Fusible Switches.

As to the failures of Terminations (Plug-On vs. Bolt-On), I have seen a Hand-Full of failed Bolt-On scenarios - commonly from stripped threads on thin Aluminum Busses or other loose Terminations at the Bus.

On the other hand, have shot trouble + repaired many, many, many-many-many "Barbeque Scenarios" oriented around Plug-On Bussing issues, as applied to heavy, continuous Loads.

On this subject, I have a Red Wirenut which is fried, due to a poor makeup situation. Found it a few Months back during the Demolition part of a T.I. Project.

I'll post an image + story later in the Photos Forum.


P.S. Please excuse any spelling air-ors (errors).
[Linked Image]

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
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