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Anonymous Poster #1

Earth Bonding in Low Voltage Bonding

10/13/2021 6:07 AM

We have designed a Low voltage electrical distribution panel which has AC as well as DC.

AC voltage limit is 415V

DC voltage Limit is 150V

This Panel is equipotential bonded to earth from all parts of the panel. Panel is powder coated.

2 Earth wires come out of the panel earth busbar , one to utility earthing and other to the earth pit.

now the question is is external earth stud in the panel required if it is equipotential bonded to earth and earth pit?

Double earthing is specified in IEEE standard but even our Panel is double earthed.

Any guidance on this is appreciated.

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Guru

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#1

Re: Earth Bonding in Low voltage Bonding

10/13/2021 7:51 AM

Has the powder coating been removed from the enclosure at the bonding contact points?

Is the earth pit bonded to the utility ground?

The purpose of bonding is to ensure equal potential from all parts.

Are the covers/doors also bonded?"

The utility ground must be bonded to the earth pit according to requirements article 250 of the NEC.

Grounding and Bonding are not the same thing.

Here is a link:https://www.nfpa.org/NEC/About-the-NEC/Grounding-and-bonding

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Anonymous Poster #1
#4
In reply to #1

Re: Earth Bonding in Low voltage Bonding

10/14/2021 2:00 AM

Has the powder coating been removed from the enclosure at the bonding contact points?

> Yes

Is the earth pit bonded to the utility ground?

> Yes

The purpose of bonding is to ensure equal potential from all parts.

Are the covers/doors also bonded?"

> Yes

The utility ground must be bonded to the earth pit according to requirements article 250 of the NEC.

> Yes

Grounding and Bonding are not the same thing.

Only thing we have not done is external panel earthing via studs. We have done it internally. Honestly i don't see any difference.

Please enlighten me if you guys see anything wrong here.

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#2

Re: Earth Bonding in Low Voltage Bonding

10/13/2021 2:14 PM

Surely the <...We...> has a Client standard or specification to work with? Or, failing that, a relevant national electrical code?

Surely the Client approved the panel schematics and general arrangement drawings prior to construction starting?

If neither of those things are to hand, then how on Earth has the <...we...> been getting away with panel design and construction to date (pun intended)?

"Better to have and not need than to need and not have." - Anon

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Guru
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#3

Re: Earth Bonding in Low Voltage Bonding

10/13/2021 5:50 PM

Generally I would say it is not required if the other two earths are used, but there may be an exception that additionally requires it depending on the standard being built to or the customer site requirements.

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Guru

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#5

Re: Earth Bonding in Low Voltage Bonding

10/14/2021 6:21 AM

The ultimate authority on this matter is the local Authority Having Jurisdiction.

All codes are dynamic and subject to interpretation and change,and the one that matters is your local authority.

Frequently they will apply more stringent rules than the code specifies.

Some local codes may require CAD bonding (Thermite bonding) of grounds,while others may not.

Some may enforce the 25 ohm rule,others may not.

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#6

Re: Earth Bonding in Low Voltage Bonding

10/24/2021 6:00 PM

If your panel is not used alone, then an external stud may be convenient.

If the panel is mounted on a skid or otherwise, with a mechanical gauge panel adjacent [or another electrical panel]; both may need a bond to the skid or to each other.

Your panel could get a big proportion of phase voltage to earth during an internal electrical fault. Any adjacent metal incidentally connected to another earth location could have a dangerous potential unless bonded.

Many electrical panels have a main earth stud which projects both internally and externally for bolting of cable lugs.

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