The 480/277V system has larger transformer most of the time, such as 2500 kVA. It can deliver higher ground fault current than 120V system. The presentation didn't include transformer impedance. The transformer impedance plays the main role of limiting the fault current magnitude, not the connector resistance. It's not likely the connector resistance can be as high as one ohms.
I have a large metal wireway, for high voltage conductors, which has a sharp edge at the opening inside the cabinet. A smooth rounded aluminum edge guard to protect the cables is being stalled. Does code require this edge guard to be grounded?
If im doing a Transformer 480/277 on the line side with flex and i punched my own hole do I need a grounding bushing ? I remember you saying in a Video that is just a practice the electricians have but you don't need too but i cant find the video now
I'm confused about a 250.92 (B)(2), for 2020, they use the word listed threaded hubs. My question is, is it listed for use in the enclosure, or listed for bonding and grounding? There's an addition in 2023, threaded entries. Is it factory made? Field attached? I also noticed, 2017, It doesn't use the listed terminology for the "threaded hubs". Might they be referring to Myers hubs in 2020?
No. Still needs to be bonded with a bonding bushing. The point is to create good connection between the 2 metal parts and as the graphic shows, the ringed knockouts aren't sufficient for 277/480VAC. Having a green ground wire inside the conduit isn't going to make that knockout handle a fault better. The metal parts need to be bonded together properly, regardless.
Bonding requirements of systems operating at over 150 volts to ground has been in previous code editions . Precautions must be taken with factory stamped concentric & eccentric conduit entries when relying on connection to provide for required metallic raceway bonding or equipment grounding path of ground faults to trip the OCPD.
Hahahah really? Ge cant just say "raising voltage while keeping watts the same decreases the amperage which is a large controbutor to heat and inefficiency."
@@MikeHoltNEC nice TY! one more question, was watching your video multipoint grounding systems but in that you mentioned another video on troubleshooting but i can not find it.
![Bonding Jumper, Supply Side [250.102, 2020 NEC]](http://i.ytimg.com/vi/slX8rAc3Mc0/mqdefault.jpg)
![Bonding Jumper, Supply Side [250.102, 2020 NEC]](/img/tr.png)
![Grounding, Objectionable Current [250.6, 2020 NEC]](http://i.ytimg.com/vi/skX9XI3de5U/mqdefault.jpg)
![Grounding, Auxiliary Grounding Electrode [250.54, 2020 NEC]](http://i.ytimg.com/vi/gg4wBI7bWgI/mqdefault.jpg)
![Grounding, System and Equipment [250.4, 2020 NEC]](/img/n.gif)
Do we need grounding bushing for solar dc circuits at 30a?
Mike, you are a great teacher and a very good man. Don’t stop the great work!
Lol, I'm 'pacing' myself so that I can continue my work for maybe the next ten or fifteen years.
The 480/277V system has larger transformer most of the time, such as 2500 kVA. It can deliver higher ground fault current than 120V system. The presentation didn't include transformer impedance. The transformer impedance plays the main role of limiting the fault current magnitude, not the connector resistance. It's not likely the connector resistance can be as high as one ohms.
The one ohm was an 'example' to see the difference in fault current and heat (squared).
I have a large metal wireway, for high voltage conductors, which has a sharp edge at the opening inside the cabinet. A smooth rounded aluminum edge guard to protect the cables is being stalled. Does code require this edge guard to be grounded?
Please post your question on MikeHolt.Ai.
If im doing a Transformer 480/277 on the line side with flex and i punched my own hole do I need a grounding bushing ? I remember you saying in a Video that is just a practice the electricians have but you don't need too but i cant find the video now
Bonding is required by 250.97. Please review that rule and let us know what you think the answer is. Hint: Bonding is not required...
I'm confused about a 250.92 (B)(2), for 2020, they use the word listed threaded hubs. My question is, is it listed for use in the enclosure, or listed for bonding and grounding?
There's an addition in 2023, threaded entries. Is it factory made? Field attached?
I also noticed, 2017, It doesn't use the listed terminology for the "threaded hubs". Might they be referring to Myers hubs in 2020?
If the hub is listed and installed per the listing instructions, then it meets the requirement of 250.92(B)(2). Which could be a Myers hub.
@@MikeHoltNEC Thank you. Really appreciate all the contributions your enterprise does for us electricians.
Thank you for this one more clarification 🙏
This is only if you don’t have a EGC ran in the pipe with the 277/480. Correct?
No. Still needs to be bonded with a bonding bushing. The point is to create good connection between the 2 metal parts and as the graphic shows, the ringed knockouts aren't sufficient for 277/480VAC. Having a green ground wire inside the conduit isn't going to make that knockout handle a fault better. The metal parts need to be bonded together properly, regardless.
Bonding requirements of systems operating at over 150 volts to ground has been in previous code editions . Precautions must be taken with factory stamped concentric & eccentric conduit entries when relying on connection to provide for required metallic raceway bonding or equipment grounding path of ground faults to trip the OCPD.
So clearly explained
Hahahah really?
Ge cant just say "raising voltage while keeping watts the same decreases the amperage which is a large controbutor to heat and inefficiency."
wow you just converted a dinosaur !! LoL, good stuff.
No way!
@@MikeHoltNEC yes way, and it did not even hurt to accept it.
@@kevinmccauley3877 Then you were never a Dinosaur...
@@MikeHoltNEC nice TY! one more question, was watching your video multipoint grounding systems but in that you mentioned another video on troubleshooting but i can not find it.
@@kevinmccauley3877 I think it's located at MikeHolt.com/NEV