Grounding of industrial control panel

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Mismail

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Hi,

I have an industrial control panel with the following:

dimensions: 600 x 600 x 250mm
Panel feeder : #14 AWG , MC cable PVC-coated , supplied from a main power cabinet (5m away from our panel) ,380 v ac 3-phase.
DC circuits inside : 24 vdc/5A power supply and another 24 vdc/20A power supply
Overcurrent devices 3A (at supply side of first power supply) & 5A (at supply side of second power supply)
the system is ungrounded (the MC feeder cable has NO grounding wire (green/yellow) )
My Questions:
----------------

1) I should refer to Table 250.122 to get the grounding conductor size for each equipment separately (size of each power supply bonding jumper by the of rated current of the upstream circuit breakers mentioned above) , is that correct?

2) what about grounding panel ? I know that all the jumpers will be bonded to the panel-board , then there should be some conductor or rod coming through the panel and fixed to the earth under the panel , correct? how to size that? what section of The NEC mentioned that ?

Thank you in advance
 
I think the armor of the MC can cable can serve as the equipment grounding conductor. Keep in mind when we talk about grounded or ungrounded electrical systems it does not have anything to do with whether it has an equipment grounding conductor or not. The equipment grounding conductor is required regardless of whether the system is grounded or not.
 
Mismail said:
2) what about grounding panel ? I know that all the jumpers will be bonded to the panel-board , then there should be some conductor or rod coming through the panel and fixed to the earth under the panel , correct? how to size that? what section of The NEC mentioned that ?
Click to expand...
You would be better off to connect an equipment grounding conductor to the source equipment than to a separate "earth" connection.
 
petersonra said:
I think the armor of the MC can cable can serve as the equipment grounding conductor. Keep in mind when we talk about grounded or ungrounded electrical systems it does not have anything to do with whether it has an equipment grounding conductor or not. The equipment grounding conductor is required regardless of whether the system is grounded or not.
Click to expand...

ok , may be i understand something wrong

as far as i know , if the system is grounded then i would collect all the grounding conductors inside the panel & connect them to grounding conductor which is in the same cable of the feeder. That is because (as far as i know) the grounding conductor is connected at the other side (main supply 380v cabinet) to some grounding means like rod or something ....that is what i understand about grounded systems

if the system is ungrounded then i wouldn't (just my view) rely on the bare conductor installed inside the feeder cable because it isn't connected to anything on the other side i.e it is not used . I would use some local earthing under the panel.

please , excuse my questions & my understanding . I apologize if i have a fault in my understanding to any concepts. I am an automation engineer NOT a power-electric engineer & I am here to learn from all of you guys , I am not going to wire anything tomorrow.
 
Ok , guys , i realized that you all talk about panels & enclosures by naming them "equipment" like (source equipment) and (equipment grounding conductor) . I understand you , but actually that confused me a little because NEC article 100 defined equipment as devices and so on and never mentioned enclosures. so when i first read 250 part VI i thought it applies to circuit components like power supply , plcs, fans , heaters , lighting (i.e devices) NOT the panel itself.

that's why , i only understood it here that you all treat enclosures & panel-body as "equipment".

Was what I understood correct?
 
Mismail said:
Hi,

I have an industrial control panel with the following:

dimensions: 600 x 600 x 250mm
Panel feeder : #14 AWG , MC cable PVC-coated , supplied from a main power cabinet (5m away from our panel) ,380 v ac 3-phase.
DC circuits inside : 24 vdc/5A power supply and another 24 vdc/20A power supply
Overcurrent devices 3A (at supply side of first power supply) & 5A (at supply side of second power supply)
the system is ungrounded (the MC feeder cable has NO grounding wire (green/yellow) )
My Questions:
----------------

1) I should refer to Table 250.122 to get the grounding conductor size for each equipment separately (size of each power supply bonding jumper by the of rated current of the upstream circuit breakers mentioned above) , is that correct?

2) what about grounding panel ? I know that all the jumpers will be bonded to the panel-board , then there should be some conductor or rod coming through the panel and fixed to the earth under the panel , correct? how to size that? what section of The NEC mentioned that ?

Thank you in advance
Click to expand...
Greetings
Are you making this system for export to the US or are you actually implementing the NEC in Egypt?
If you are in Egypt are you on a 380Y220 50Hz and bringing 3 hots to the panel (brown, black and gray) or 680Y380 50Hz bring two wires L-N (blue and brown)?, with a 14AWG (or 2.5mm) wire feeding the panel whats the breaker or fuse size in the main power cabinet protecting the control panel 16Amps? one pole or 3 pole? Is it on an RCD?
Can you post some photos of the main power cabinet ?
What color conductors is standard to identify a grounded circuit conductor there? light blue?
All the fixed to the earth connections should take place in the main power cabinet not the control panel.
5m is pretty short I would just replace the cable with one that contained a green with yellow stripe, there are other options also.
Cheers
 
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