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, www.bussmann.com 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).]

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....]

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

Hi Dan, 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?
wirewiz

Sparky,

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 intent...safety 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).]

wirewiz,

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.

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? ERWIN

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

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.

Dan,

Thanks again for your involvement here. I had some direct links added to your initial post (and fixed the Bussmann.com 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.


Bill


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

Dan,

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?

Bill

Erwin,

In regards to the device that does not trip, I was not trying to single out one manufacturer. It can happen with any manufacturer, where the conditions of testing and maintenance are lacking. Although, I have heard similar comments in regards to your conclusion...however, I have no first hand knowledge of that, only second hand information about that and other various manufacturers.

Wirewiz,

I have searched the Bussmann SPD in regards to finding supporting information of replacing all three fuses, but have found nothing in print. However, I believe this to be a good maintenance practice. Perhaps, you can point out that the cost of an extra fuse is a minor cost in comparison to what could create a future maintenance cost.

Dan

Warren,

Sorry the links didn't work as expected. Perhaps if you can just go directly to our website, click on services, then on-line training you can get to our presentations which are downloadable. All of them are posted and available for download. If you cannot access this by doing the above, please email me with you address and I will send you a CD with all of the presentations. I can include any other information on this CD that would be of interest to you.

Dan

Bill,

Thanks again for letting me participate in your discussion and adding links to our information.

In regards to your question on the overcurrent protection knowledge needed by the average electrician, I would suggest the below three most important points, in order of importance.

1) Always make sure you know the available fault current and apply an overcurrent devices with adequate interrupting ratings per NEC 110.9. This is the most overlooked and important item of proper overcurrent protection. This is especially important for the service equipment and first level distribution panelboards. The application of current-limiting devices makes this less of an issue in these applications due to high interrupting rating capabilities.

2) Be aware of proper protection requirements of electrical systems components per NEC 110.10 and NEC 110.3(B). Many components may require a specific device, per NEC 110.3(B) in regards to the listing and labeling...such as HVAC equipment. This can also be extended to motor circuits, regardless of the single-phasing concerns. Fuse protection (with solid state overloads and single phase protection) are still the best solution for these applications.

3) Safety is the common thread in overcurrent protection. The first two points have addressed safety in regards to systems and electrical components, because this is the most common concern. However, when you add the human factor...this hits home even more and this is why this has been a major focus recently. Anyone who has seen an electrician with third degree burns understands what I am referring to with this discussion. I am not trying to imply that fuses solve all the problems in protecting the electrician, however they certainly help to offer a component of the total solution. The bottom line is that fuses can provide reliable overcurrent protection and can lessen the dangers to electricians in certain situations.

Dan,

Welcome Aboard!

I look forward to discussions regarding SCA calcs and such with you and the members in this forum.

I'll toss some scenarios out when time allows.

Scott SET

In an effort to suggest methods to provide human safety to the maintanace crews, current limmiting fuses and breakers help reduce arc flash significantly.

Dan,
Is it becoming more common for industrial facilities to use fuses instead of MCPs or MCCBs for short circuit protection in motor control centers. I was in locations several years ago that were doing this on the fuse manufacturers' recommendation due to the increased reliability and accuracy of fuses over breakers. These facilities had processes that could lose a lot of profit from nusiance tripping of breakers and time down replacing motors whose breakers did not trip.

Thanks Dan
wirewiz

Dan,

I just came across this Article at the CEE News Website and I figured I would share it with everyone.

Cooper Bussmann now offers online educational and training presentations on the NEC

Bill

gpowellpec,

In response to your question on fuses vs. circuit breakers in motor circuits:

I have not heard any issues with nuisance tripping of fuses or circuit breakers. However, I have heard issues with MCPs (and this is why the limits on sizing keep rising).

It seems like the trend lately has been to go to circuit breakers and MCPs. Why, because they think that the resettable feature of breakers is better than having to replace fuses and they do not have to have a qualified electrician to do this...just an operator.

However, the flaw in this logic starts with choosing convenience over protection and safety. Why?
1) The branch-circuit device in motor circuits (or as termed in 430.52, is the branch-circuit, short-circuit, and ground-fault protective device) is there to protect against short circuits. The overload relay is there to protect against overloads. OSHA requires that circuit breakers and fuses can not be reset unless the device opened due to a known overload. If you think about it, the fuse or circuit breaker is typically sized per 430.52 at 175% or 250% respectively because it is there only for short-cirucit protection. The overloads sized at 115-125%. Thus, if the fuse or circuit breaker opens, it is probably due to a short-circuit condition and the problem must be corrected before the device can be reset. Thus, resettability of breakers is really a mute point.
2) Given the above, if circuit breakers are used and since they are resettable would the possibility be a person to just try and reset the device before checking out the problem? This could be an issue unless OSHA rules are followed.
3) As discussed previously, the device is there for short-circuit protection. More specifically, short-circuit protection of the motor circuit. If you look in UL 508, damage is allowed to motor circuit components in the standard and high interrupting capacity tests. As long as the door does not blow open, contacts can be welded and overloads burned open which can require replacement and additional downtime concerns. However, if the device is tested to IEC 60947-4-1, Type 2 protection can be verified which assures no damage to the motor circuit components, other than light contact welding that is easily seperable. How do they achieve Type 2 protection? You need a very current-limiting device such as a Class RK1 or J fuse.
4) Continuing on this and the testing per UL 508. This testing is based upon the door closed, what if someone is troubleshooting the motor starter "hot" with the door open and creates a fault...how much protection will they have with this door open?? This too can be a safety issue that needs to be addressed if working equipment "hot".

The points I have mentioned above have been used to convert a number of large industrials from circuit breaker MCCs to fusible MCCs.

Hope this helps.

Thanks,
Dan

Ron,

You have raised a great point. Current-limiting overcurrent devices, such as fuses, can greatly reduce arc flash.

Just be clear though...realize that this is only part of the solution. When discussing safety fuses are not the only answer, just a part of the solution. Additional safety considerations, such as protective clothing and proper procedures are also crucial.