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Overcurrent Protection - Bussmann #8569 03/27/02 07:33 PM
Joined: Mar 2002
Posts: 29
Dan Neeser Offline OP
I am Dan Neeser with Cooper Bussmann and have been requested to participate in the forum discussion on topics regarding overcurrent protection.

Just so you guys know my background, I have been involved in training our customers on all overcurrent protection topics for the past five years with Bussmann. I have conducted numberous Overcurrent Protection Seminars from coast to coast and been active in IEEE, IAEI, NJATC, NECA, IBEW, and NFPA. Prior to coming to work for Bussmann I was a Sales Engineer for Westinghouse/Cutler-Hammer, so I can address switchgear and circuit breaker questions as well.

Feel free to ask me any questions you may have, either through the forum (which I check periodically) or via email (which I check daily).

In addition, I have listed some areas on our website, that may be of interest:

From the Home Page,
- Go to Application Info, then Pubs and Articles to view:
1) 2002 NEC Code Changes
2) NE02 - 2002 NEC Requirements for Overcurrent protection (also for NE99)
3) SPD - Selecting Protective Devices (all you need to know about overcurrent protection)
4) Series Rated Combinations (Info and Charts)
5) EPR-1 - Electrical Plan Review (Short-circuits, caculations, interrupting rating etc.)
6) Tech Spec and Tech Talk - Technical Newsletters on overcurrent protection

- Go to Services, then go to On-line training to view:
1) 2002 Code Changes presentations with script (some narrated)
2) Overcurrent Protection Topics and training presentations with script.

- Go to Services, then Safety Basics (Electrical Safety Info)

- Go to Product Info, then catalogs or products
1) under products, look at the Power Module if you need a fusible shunt trip switch for elevator installations which require shunt-tripping.

Again, if you have any questions, please do not hesitate to contact me.

(Some Direct Links added by Webmaster)

[This message has been edited by Webmaster (edited 03-29-2002).]

Work Gear for Electricians and the Trades
Re: Overcurrent Protection - Bussmann #8570 03/27/02 09:17 PM
Joined: Oct 2000
Posts: 5,389
sparky Offline
Hello Dan & Welcome.

No doubt your experience will be a refreshing addition here.

Navigating the links you've provided had brought me to..... 430.102 and it's 02' change.
I wonder often why changes like are made, as done here.
I also wonder what everyone else is doing to comply......
[which is why i hang here....] [Linked Image]

[This message has been edited by sparky (edited 03-27-2002).]

Re: Overcurrent Protection - Bussmann #8571 03/27/02 09:48 PM
Joined: Jan 2002
Posts: 122
wirewiz Offline
Hi Dan, [Linked Image] Nice to have someone with your specialty here! I was lucky enough to take a bussman seminar a few years ago and someone in the class brought this question up. Is it possible for fuses to wear out over time? First time I ever heard the guy giving the class say " thats a good question, I don't know..." since then I have always wondered?

Re: Overcurrent Protection - Bussmann #8572 03/28/02 10:45 AM
Joined: Mar 2002
Posts: 29
Dan Neeser Offline OP

Thanks for looking through our information and replying to my message.

In regards to your question on the change in 430.102. I hope you agree this is a good change. It is something that IBEW fought very hard for and something that Bussmann supports. The reason the change occurred was that the previous exception in 430.102 (eliminating the disconnect at the motor provided the disconnect for the controller was lockable) was becoming the rule as opposed to the exception. This tended to spur the elimination of a local disconnect for motors and tended to cause the working of motors "hot" instead of going back to the controller disconnect and properly locking and tagging out the disconnect.

The revised text still permits the exception provided a safety procedures with proper lockout/tagout procedures are followed and preformed by qualified person or if additional hazards would result from a local disconnect. This is really the and I think the change promotes safer installations. It also requires a permanently installed locking mechanism for the controller disconnect...again I believe this improves safety.

For commercial installations, I believe most people will be requiring a local disconnect "insight" of the motor to comply with the code change. For industrial installations, the maintenance practices and application would require analysis to determine if the exceptiosn can be met. If unknown, the disconnect at the motor would be recommended.

[This message has been edited by Dan Neeser (edited 03-28-2002).]

Re: Overcurrent Protection - Bussmann #8573 03/28/02 10:55 AM
Joined: Mar 2002
Posts: 29
Dan Neeser Offline OP

Great question. The simple answer is no provided the fuse does not see any overcurrents and is properly sized. That being said, nuisance opening could be a problem due to a couple of reasons. The most common is sizing the fuse too close to a load that has a high inrush current. This can occur in a motor or transformer application that has an unusually high inrush. Also, if you have a three-phase installation and two of three fuses open, there is a chance that the third fuse, which did not open has been somewhat fatigued. That is why it is always recommended to replace all three fuses, and all with the same manufacturer.

The good thing is that fuses only open when excess current is present and they always open the circuit when that overcurrent is present. This greatly improves the reliability and protection of the system over time. It is certainly better than having a device that doesn't trip when it should.

Re: Overcurrent Protection - Bussmann #8574 03/28/02 09:10 PM
Joined: Nov 2001
Posts: 273
circuit man Offline
hi dan,glad see some new info from a guy that does it every day. on that thing you say doesn't trip, wouldn't be refrering to the good old FPE breakers would you? [Linked Image] ERWIN

Re: Overcurrent Protection - Bussmann #8575 03/29/02 12:28 AM
Joined: Jan 2002
Posts: 122
wirewiz Offline
Dan, Thanks for the explanation is there any literature bussman has that I can show a customer when they don't want to replace all 3 fuses? Wirewiz

Re: Overcurrent Protection - Bussmann #8576 03/29/02 01:12 PM
Joined: May 2001
Posts: 176
WARREN1 Offline
Hi, Dan, good to have you providing a lot of insight for the members of this board.
I tried your link, but our firewall would not let it work due to the comma located at the end, however, I visited through a search engine. Looks as if there are several presentations of on-line training that would be very interesting, but are not yet available. Please let us know as they make their debut.
Again, its good to have you here.

Re: Overcurrent Protection - Bussmann #8577 04/01/02 01:19 PM
Joined: Oct 2000
Posts: 3,974
Bill Addiss Offline

Thanks again for your involvement here. I had some direct links added to your initial post (and fixed the link). I hope this will be a rewarding experience for all.

Anybody got any good questions about Overcurrent Protection, Fuses, etc?
Now's the time to ask them.

[Linked Image]

[This message has been edited by Bill Addiss (edited 04-01-2002).]

Re: Overcurrent Protection - Bussmann #8578 04/03/02 10:02 AM
Joined: Oct 2000
Posts: 3,974
Bill Addiss Offline

I hope that this isn't too big a question, but how much does the 'average' electrician need to know about Overcurrent protection and why?


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