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Author Topic: Where to bond Ground with DG and other Q's  (Read 5676 times)

Nitin Sidhu

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Where to bond Ground with DG and other Q's
« on: February 15, 2015, 02:39:14 pm »

Hello!

A few questions propping up in my head.

We are moving into a space where diesel generator power, 3-phase, would be supplied to us instead of the 1-phase house power.

1.Mostly this would be a 4 core cable drop, without a grounding conductor available to the DG chassis or such. So Neutral bonding would need to be either local, or we carry a 100mts of single core to connect with the DG. What is correct ?

I would consider bonding the neutral with the ground at the main 3-ph distro we would then carry (for a start, a simple 4 pole isolator with a neutral and ground bus bond at the input, being fed to an 63 or 100 amp isolator)

2.What happens if the Neutral at the distro breaks ? Unbalanced circuit and a 440 to fry the equipment ? How to avoid ?

3. The max I see of CEE Form connectors out here are rated at 63amp, 5pole. Now, the amperage is ample for my needs. What I do not understand, is that I am sure a 125Kva genset is capable of delivering a lot more current that 63 amps, yet all I have seen here is a 63 amp receptacle on an input. What is the standard receptacle use for higher loads ?

I have some questions about RCCB/RCBO and local circuit MCB's that I hope to post soon too.

Thank you all for your time.

Regards,
Sidhu
« Last Edit: February 15, 2015, 11:08:49 pm by Nitin Sidhu »
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Stephen Swaffer

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Re: Where to bond Ground with DG and other Q's
« Reply #1 on: February 15, 2015, 03:40:13 pm »

Ground and neutral need to be bonded in ONE place.  This is usually at the first disconnect-so if there is a disconnect at the generator do it there otherwise at main distribution.  Either way,  there needs to be ground between the generator and the main distribution as well as ground rods at the generator and ideally at main distribution as well.

By DG, I assume you mean diesel generator?
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Jonathan Johnson

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Re: Where to bond Ground with DG and other Q's
« Reply #2 on: February 16, 2015, 12:06:03 am »

Obligiatory Disclaimer: I am not an electrician.

You should be able to have two bonding points, so long as there is only a single, common grounded neutral conductor between the bonding points.

At the generator, drive a grounding rod. Bond the grounding rod, generator frame, and neutral. (If the neutral is already bonded to the frame, bond only the ground rod and the frame.

At the distro, drive another grounding rod (grounding electrode conductor). Bond it to the EGC (equipment grounding conductor) and neutral.

There should be no other ground path (no EGC) between the distro and the genset besides the neutral, whether it be an intentional EGC/GEC or an incidental connection such as an audio shield, lighting kit supplied directly from the genset bonded to a truss that also has grounded audio equipment attached, or personnel that can come into contact with both grounding systems (distro and genset). It's a remote possibility, but incidental connections could result in ground loop hum, or personal injury or property damage.

(If you have more than one distro, such as one for audio and one for lighting, it gets ugly. Bonding at both distros could result in issues when something conductive comes between equipment connected to disparate distros. In that event, both distros must share a single, common bonding point, whether it be an EGC from each run back to the genny or an EGC run between the distros. This is a similar issue to what you would face when pulling power from two different homes for a street fair, as has been discussed previously in this forum. The homes have two different bonding points, possibly joined only by the neutral, which could be at different potentials.)

This is fundamentally no different than what is common for utility distribution, where neutral, ground (EGC), and ground rod are bonded at the utility transformer; neutral, ground (EGC), and a separate ground rod are bonded in the service entrance panel of the home, and there is only a single, common grounded neutral conductor between the transformer and the service entrance.

Of course, your AHJ has final say in the matter.
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Nitin Sidhu

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Re: Where to bond Ground with DG and other Q's
« Reply #3 on: February 16, 2015, 12:27:03 am »

Than you Stephen, I would *assume* that the neutral is already bonded to the ground at the generator panel, which is then also grounding the generator chassis. So if I could run a cable to the generator chassis, I would be good.

However, if that is not possible, then bonding our first disconnect is our best alternative.

Now, can I have the neutral permanently bonded in my main dsconnect ? This is ask if I do get a 5th grounding conductor also from the DG, then the Neutral bond is happening twice, at the DG and our first disconnect.

Thank you.
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Nitin Sidhu

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Re: Where to bond Ground with DG and other Q's
« Reply #4 on: February 16, 2015, 12:35:00 am »

Obligiatory Disclaimer: I am not an electrician.

You should be able to have two bonding points, so long as there is only a single, common grounded neutral conductor between the bonding points.

Ah thank you!

So a 4core cable feeding my distro, which would be grounded is good. Thank you again.

Regards,
Sidhu
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Stephen Swaffer

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Re: Where to bond Ground with DG and other Q's
« Reply #5 on: February 16, 2015, 09:00:20 am »

 >:(

Than you Stephen, I would *assume* that the neutral is already bonded to the ground at the generator panel, which is then also grounding the generator chassis. So if I could run a cable to the generator chassis, I would be good.


This is a safety issue-do not make an assumption, find a way to test/visually verify.  It is essential that the generators frame have path (bond) from the neutral.

While Jonathan is correct in that 2 bonds should work, here in the states utilities are governed by a different set of rules.  The NEC, which most of the rest of us are governed by does not allow 2 bonds.  Mainly because of the potential hazards caused by incidental or intentional metallic paths between the generator and the distro.  So, if you do opt for 2 bonds, you need to take extra care in that area.

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Nitin Sidhu

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Re: Where to bond Ground with DG and other Q's
« Reply #6 on: February 16, 2015, 09:27:38 am »

Yes Stephen!

Thank you. My assumption is based upon the fact that i have not measured.
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Jonathan Johnson

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Re: Where to bond Ground with DG and other Q's
« Reply #7 on: February 16, 2015, 12:40:37 pm »

I understand that in India, doing everything safely and properly is not always possible, because few people are knowledgeable AND concerned about safe and proper practices, so may be unwilling to put forth the effort and expense to do it right.

My hat is off to you, Nitin, for trying to do things right. The more you learn and the more you do, the more you will educate your peers. And to the extent that reduces injury, your world will be a better place.

(Cultural note: in Western culture, removing one's hat in the presence of another is a sign of respect. Historically, it signifies subservience or an inferior social status, such as a subject removing his head covering when in the presence of the king. As a gesture, it is similar to the military salute, which is initiated by the junior rank.)
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Nitin Sidhu

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Re: Where to bond Ground with DG and other Q's
« Reply #8 on: February 16, 2015, 09:44:54 pm »

I understand that in India, doing everything safely and properly is not always possible, because few people are knowledgeable AND concerned about safe and proper practices, so may be unwilling to put forth the effort and expense to do it right.

My hat is off to you, Nitin, for trying to do things right. The more you learn and the more you do, the more you will educate your peers. And to the extent that reduces injury, your world will be a better place.

(Cultural note: in Western culture, removing one's hat in the presence of another is a sign of respect. Historically, it signifies subservience or an inferior social status, such as a subject removing his head covering when in the presence of the king. As a gesture, it is similar to the military salute, which is initiated by the junior rank.)

Haha! Thank you Jonathan! All good my man, even though we do have elephants walking around in cities, seriously, but remain otherwise quite well tuned into "western" culture.

That said, it is a pain here, and im constantly paranoid.

Cheers!
Sidhu

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Nitin Sidhu

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Re: Where to bond Ground with DG and other Q's
« Reply #9 on: February 18, 2015, 06:15:54 am »

And extension of the above situation.

So I built a small 3-ph distro, input 3p+N, grounded locally. Working well.

Now I am building a generator terminal box, this will have a 4pole terminal, feeding an isolator to a CEE form plug, further feeding the 3ph distro.

As I am only being supplied with a 4core cable (3p+N) from the power source, what happens if we get a fault here ? What protection to take here ?

Also, in 3phase systems, what happens if 2 live phase cables were to come into direct contact ? Will a 4pole circuit breaker trip ? Or does it rely on current flowing through the phase and Neutral wires only ?

Thank you!
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Re: Where to bond Ground with DG and other Q's
« Reply #9 on: February 18, 2015, 06:15:54 am »


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