Coordination, Overcurrent Protective Devices
ฝัง
- เผยแพร่เมื่อ 12 ต.ค. 2023
- This video is extracted from Mike Holt's Understanding Electrical Theory Library www.mikeholt.com/Theory. For additional information call 888.632.2633.
For almost 50 years, Mike Holt Enterprises has been providing quality training products for the electrical industry that help people learn the Code, prepare for exams, fulfill continuing education, and improve their electrical knowledge.
Visit www.MikeHolt.com for exam preparation tips and training, instructor and curriculum support, continuing education options, free videos and graphics, and so much more.
Happened to me at work. Old building with a brand new main panel- 2000A breaker tripped. Buildimg with labs and experiments that had been testing for years. Everyone freaking out. Lucky for me i was aware of instantenous tripping and new that a short had most most likely been the cause. Had a feeling there had to be a tripped small breaker somewhere. Took two hours to go to each floors electrical room and to find panels in other places to see that everything was ok. Finally found a three phase 480v 15amp tripped breaker for a compressor which i checked for ground fault. I left that breaker tripped and went ahead suited up and energized the main. Power was restored. Alittle of knowledge, safety and common sense goes along way
Wow, a 2000A breaker... My largest was 800A.
The best Sensei in the Electrical World.POINT.Thanks Mike also for responding to all guys that try to reach out to you. Big Cheers from Chicago.
Thank you, you guys are very important to me.
In the apartment I lived in 8 years ago a cookie sheet fell behind the stove and shorted the prongs of the 3 wire range plug and tripped the main that was in the mechanical room of the building, but the 40 amp breaker in my unit didn't trip.
Lol
Hey Mike, thanks for all the work you do. Ive learned so much through your programs. I constantly find myself going back to rewarch & reread material. Your journeymen program aided me in getting licensed in Chicago. I passed with a 93% the first time. Meanwhile, my brother did not use your program, he failed twice and finally got it on his third try with a 71% (70 passing) lol. You are clearly doing something right. Thanks a lot! I love the content. I plan on getting the estimating program soon as now i am an electrical contractor and i cant wait to see what great info is packed in there Thanks a lot Mike!
Thank you for the great news and the kind words.
I see this happening on a regular basis. (Industrial) Very frustrating.
If only there was a way to coordinate gfci breakers? I once (20+ years ago) by chance shut down the ENTIRE Chevron world headquarters in san ramon ca by simply working on lighting and messing with the neutrals in a ceiling light box. Yes, the entire building was on gfci close to or at the service. My boss was pissed but not at me. Rather at whoever designed such a thing. An interesting day to say the least.
Very interesting.
OMG... I know the feeling. I was teaching at Texas Instruments World Headquarters and the power to the entire facility turned off for about three hours! People were freaking out. The 'high-voltage' fuse at the street somehow dropped out... true story.
Wow love the look of these new videos with the filming room, cameras, etc...every code cycle Mike gets more high tech with the filming!
Glad you like them!
Awe man.. look at those updates!!! looking great!!!
Thanks, we are really getting to the next level. One day at a time.
OMG. I cant believe that I just found your channel.
the materials are so useful for my upcoming PE exam
The PE exam has significantly increased the NEC portion of the exam. Enjoy
Hi,your lectures are inspiring and informative.Thank you for these.
Oh... thank you. God Bless
I think this is a topic that needs more time spent on it, as so many electricians in the field simply have no idea how this works. Working in a data center, I have experienced two avoidable breaker coordination failures. In one instance, a contactor flashed over internally, tripping the internal 600A breaker of a UPS unit, the upstream 600A breaker in the adjacent bypass panel, and the further upstream 600A supply breaker in the main electrical room. All three breakers have tunable magnetics, and were left at the factory setting of lowest instantaneous threshold, when the upstream breakers should have been set to the highest instantaneous threshold. At least the main breakers above those were all computerized.
The second incident had a 20A PDU breaker trip, a 30A breaker in a busway tap, and the 225A busway main breaker trip simultaneously. Again, the 225A breaker was dialed to the most sensitive magnetic setting from the factory, when it should have been changed to the least sensitive. Unfortunately, circuits near busways can have high short circuit currents just like circuits near panels.
Yikes!
Thank you Mike 🙏
An important task, especially for fire protection types of equipment such as the Fire pump panel that feeds two or more individual pumps. Each of the main breakers and sub-breakers needs careful coordination.
When I design the Nuclear Command Center for PWRs, I also need to consider that long-distance low voltage routing brings too much high impedance and makes the instantaneous rate, not enough sensitive to trip in time.
Well, I never considered the length of the conductors (impedance) when designing 'selective coordination.'
I was working on a 20A 277V lighting circuit and pinched a wire in the fixture so when I turned the breaker back on, not only did the 20A breaker trip but so did the 800A main!😅
OMG… I did the same thing and tripped a 800A main. Freaky if you don’t understand, and I didn’t understand.
Mike, you are basically A living NEC book;)!
Just what I do everyday to help others.
A main breaker in the panel seems very handy until you learn they may not reset if finicky.
Hey Mike... I just wanted to ask whether 408.3A(3) is meant to apply to panelboards as well. Please respond. Thanks.
I don't see 408.3(A)(3)...
What cycle are you using?
More importantly what cycle are you using?
408.3(A)(3) was in the 2017... it is now 408.3(A)(2) in 2020, since our jurisdiction is using this cycle now. Just an fyi if it helps. Cool video. Thank you for your continued knowledge @MikeHoltNEC. I will apply it to my study.
I’m still not sure how you selectively coordinate
Neither do I. This is an engineering design issue by those that are trained in this field.
Mike, whats your diet like? You are looking young.
I'm not a 'food freak,' I just try to avoid process foods and fast food joints. I love my steak and ribs!
Very interesting. Not something engineers are likely to cause, more so to be caused by cheap product purchasing by the electrical contractor.
The electrical contractor just installs what the engineer specs out. If the engineer wants a 'selective coordinated system' then it needs to be designed for that feature.
What is the point of this video? It is just a 15 minute explanation of what selective coordination is. There was 2 minutes of information that was repeated over and over. I feel like I’m missing something.
Nope you didn’t miss anything…
I feel like you act like this at work!! If this video isn’t for you, just move on. Sometimes people like to listen to discussions, there is a new electrician studying everyday. Get an attitude adjustment bud
@@3yolafeddy654There is much more free will involved in watching a TH-cam video as opposed to having a conversation at work, which makes the two less than comparable.
Nevertheless it is true, I do act like this at work. I make a point of being effectual and efficient with language during my discussions of technical matters. It is not considerate to burden people with casual banter of dry topics when there are so many more impactful things to be discussing.
Another bad habit of people particularly in corporate America in the desire to say words and sentences with no meaning, particularly during company meetings. It too is a burden to everyone involved, and makes leaders look desperate and foolish.
Death and life are in the power of the tongue: and they that love it shall eat the fruit thereof.
@@raymonddonovan3297 your banter burdens people in life, and now on the internet, get a grip. Lay off the pvc glue
Ah yes, another of my people!