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Topic Title: inverter grounding
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Created On: 25 February 2010 09:19 AM
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 25 February 2010 09:19 AM
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nigel24

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Hi to every on the forum,

The company i workfor has invested in a Victron Pheonix inverter compact. The source is 12v dc-240VAC.
The problem is that the manual states that the chassis has to be grounded. I have decided to do this by using earth spikes and an earth lead from the spike to a suitable ground. Because the inverter is to be a portable piece of kit, used for TV outside broadcasts, do i have to use special earth bond cable, as this will not be protected when in use. The distance of this lead will only be a few meters. I have looked in the 17th edition of the regs, and i couldn't see any thing about this in special installations. I welcome your input for any ideas on this topic or safety areas i need to look at. The AC output has an RCD fitted.
Thanks.
 25 February 2010 09:53 AM
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zeeper

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Have you looked at bs 7671 : 2008
reg 717.1 and/or 711.1

Not sure why you would need a special cable for the temp earth spike, other than it being flexible.
 25 February 2010 10:26 AM
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gkenyon

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See also BS7909.

I believe that there are cases stated in that standard, where vehicles are not anticipated to have a connection to earth ?

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Eur Ing Graham Kenyon CEng MIET TechIOSH
 25 February 2010 06:06 PM
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jleltd

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How would this product be used on the move are you sure the grounding does not mean the 12v chassis ground?

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James
 25 February 2010 10:29 PM
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gkenyon

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Well, now that's an interesting statement. What is actually meant by "grounding"?

In the EU (including UK), "earthing" means connection with the means of earthing, and/or with the general mass of the earth. The term "grounding" is not defined. But in the US, "grounding" is substantially what is meant by "earthing" in the EU.

Conclusion: The "Chassis" of the vehicle is, strictly, neither "earth" nor "ground" unless you purposefully make that connection with the generall mass of the earth.


Please be careful with answers at this point - my question has a purpose!

-------------------------
Eur Ing Graham Kenyon CEng MIET TechIOSH
 25 February 2010 11:13 PM
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colmessy

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"Grounding " an American termology which defines a fixed voltage reference normally taken as 0V, not a direct connection to earth

Colin
 26 February 2010 08:57 AM
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gkenyon

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Originally posted by: colmessy

"Grounding " an American termology which defines a fixed voltage reference normally taken as 0V, not a direct connection to earth



Colin
Colin,

Is that definition based on ANSI/IEEE standard reference, and/or National Electrical Code?

Similarly in the EU I see instructions telling me to "earth" a suppressor to a motor casing - but the motor is part of a double-insulated machine . . . but we know that this is strictly an incorrect use of the term "Earth".

I Quote from National Electrical Code Article 100 (Definitions):

"Ground, the earth"

"Gounded (Grounding). Connected (connecting) to ground or to a conductive body that extends the ground connection."

etc.

As far as I know, in the NEC, all references to "grounding" are connecting with the general mass of earth, as with "earthing" in the UK.

-------------------------
Eur Ing Graham Kenyon CEng MIET TechIOSH

Edited: 26 February 2010 at 09:15 AM by gkenyon
 26 February 2010 09:07 AM
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FizzleBang

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I'm struggling to see why this piece of kit need referencing to earth.

We do that sort of thing with fixed mains installations becasue the remote source of energy is also referenced to earth.

Shirly this just needs reference to the vehicle chassis?


Paul

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To me, to you
 26 February 2010 09:33 AM
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gkenyon

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Originally posted by: FizzleBang

I'm struggling to see why this piece of kit need referencing to earth.



We do that sort of thing with fixed mains installations becasue the remote source of energy is also referenced to earth.



Shirly this just needs reference to the vehicle chassis?
Why?

See Clause 7.4.2.3 of BS7909 "Where a generator supplies a temporary electrical system that is electrically separate from all other electrical systems, a connection from the generator to the general mass of earth is not essential. If this methos of supply is used, extreme care should be taken to ensure that there is no intended of casual interconnection with any other electrical systems, such as via earth referenced signal cables, CPCs, esposed or extraneous conductive parts."

But caution is required with methods of protection and fault detection (i.e. failure of the separation) - normally it's more difficult to ensure electrical separation, than provide temporary earthing.

There's a lot of information in BS7909: 2008, in particular Annex C has a lot of information on earthing arrangements and temporary systems, and does cover broadcast etc. vehicles.

I don't think this is an easy topic.

But the Original Post does contain a clue.

If the manufacturer says it needs "grounding", than without other information, some kind of "earthing" is what's needed. See previous definition from National Electrical Code.

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Eur Ing Graham Kenyon CEng MIET TechIOSH
 26 February 2010 09:33 AM
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gkenyon

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Originally posted by: FizzleBang

I'm struggling to see why this piece of kit need referencing to earth.



We do that sort of thing with fixed mains installations becasue the remote source of energy is also referenced to earth.



Shirly this just needs reference to the vehicle chassis?
Why?

See Clause 7.4.2.3 of BS7909 "Where a generator supplies a temporary electrical system that is electrically separate from all other electrical systems, a connection from the generator to the general mass of earth is not essential. If this methos of supply is used, extreme care should be taken to ensure that there is no intended of casual interconnection with any other electrical systems, such as via earth referenced signal cables, CPCs, esposed or extraneous conductive parts."

But caution is required with methods of protection and fault detection (i.e. failure of the separation) - normally it's more difficult to ensure electrical separation, than provide temporary earthing.

There's a lot of information in BS7909: 2008, in particular Annex C has a lot of information on earthing arrangements and temporary systems, and does cover broadcast etc. vehicles.

I don't think this is an easy topic.

But the Original Post does contain a clue.

If the manufacturer says it needs "grounding", than without other information, some kind of "earthing" is what's needed. See previous definition from National Electrical Code.

-------------------------
Eur Ing Graham Kenyon CEng MIET TechIOSH
 26 February 2010 10:54 AM
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Veglen

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Hope you don't mind me giving you my take on this one. I can't help thinking some of you are reading far too much into it.

Grounding in the automotive industry means connection to the chassis ground. i.e vehicle chassis. Sounds to me like the metal body of the inverter (chassis), requires connection to the chassis of the vehicle (known as grounding) in order to prevent noise caused by what would be termed as Ground Loops! Which is basically electrical interference otherwise known as alternator whining.

Hope this helps

V

Sorry, should have said such as alternator whining amongst others!

Edited: 26 February 2010 at 11:03 AM by Veglen
 26 February 2010 11:39 AM
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nigel24

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Hi Graham,

Thanks for your input on this subject.

Ican see that this topic is causing quite a debate. I thought i would include the paragraph from the manual to clear any misunderstading with this grounding issue.

"The neutral wire of the AC output of this inverter is connected to the chassis. This is to ensure proper functioning of the GFCI or RCCB to be installed in the AC output of the inverter. (i presume RCD is the same as a GFCI)?
The chassis of the product must be connected to ground, to the frame of a vehicle or the ground plate or hull of a boat".

These inverters are used a lot for marine use. I have e-mailed the company about this, but never recieved a reply, maybe they thought it was a stupid question!
 26 February 2010 11:51 AM
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gkenyon

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Originally posted by: Veglen

Hope you don't mind me giving you my take on this one.
Not at all.

I can't help thinking some of you are reading far too much into it.
No, just the appropriate parts of the relevant UK standards for mains electrical installations in vehicles for public broadcast - BS7671 and BS7909. Neither of these use the term "Ground", but the US equivalent of BS7671 does - exactly where we use the term "earth".



Grounding in the automotive industry means connection to the chassis ground. i.e vehicle chassis. Sounds to me like the metal body of the inverter (chassis), requires connection to the chassis of the vehicle (known as grounding) in order to prevent noise caused by what would be termed as Ground Loops! Which is basically electrical interference otherwise known as alternator whining.
Ground loops are not just known as (or for) "alternator whining", but again, in the mains electrical world in the EU, we tend to use "earth loop". It's best not to confuse electromagnetic compatibility terms such as "ground loop", which actually came from a US standard on what we now call "electromagnetic compatibility", with power "earthing" terms.



Hope this helps
Only in illustrating the precise point I wanted to make earlier when I said "Please be careful with answers at this point - my question has a purpose! "

That point is:

There are many uses of the term "earth", "ground" and "chassis", and combinations thereof, by manufacturers in their installation, operation and maintenance manuals, and sometimes by specifiers in designers in their documents.

The problem is, these terms are meant in a variety of ways, often not really the way the terms "earthing" and "grounding" are defined in the relevant standards.


And this mis-use causes the problem we've identified here.

One answer "Just connect it to the Chassis Ground, it'll be OK" clearly contradicts the recommendations in BS7909 as I pointed out in an earlier post . . . is that OK? Would a court find it acceptable?


The course of action for the Original Poster is:

1. Read and understand the relevant requirements in BS7909 and BS7671

2. Seek clarification from the Manufacturer.

3. Ensure that the appropriate requirements of the standards and manufacturer are incorporated in the design.


Since this is Work Equipment in the UK, PUWER applies as well as the general obligations of Health & Safety at Work etc. Act. and the Electricity at Work Regulations.

We need to be mindful, that in the UK, the duty to provide adequate earthing (where it is required for safety) in the Electricity at Work Regulations is an ABSOLUTE duty - you MUST do it, as opposed to "So far as reasonably practicable" that's a quailificaiton in some other parts of the Electricity at Work Regulations.

See Regulation 8 of Electricity at Work Regulations.

-------------------------
Eur Ing Graham Kenyon CEng MIET TechIOSH
 26 February 2010 01:07 PM
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gkenyon

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Originally posted by: nigel24

Hi Graham,



Thanks for your input on this subject.



Ican see that this topic is causing quite a debate. I thought i would include the paragraph from the manual to clear any misunderstading with this grounding issue.
No problem with the debate - as I pointed out, this often occurs when people use "ground", "earth" or "chassis" indiscriminately. Most of the time, I work with IT, and there you get many requests for different types of "earth", e.g. "clean earth", "chassis ground", etc. - all of which can be resolved using standards like EN50310.

Anyway, including this extract makes things a little clearer.



"The neutral wire of the AC output of this inverter is connected to the chassis. This is to ensure proper functioning of the GFCI or RCCB to be installed in the AC output of the inverter. (i presume RCD is the same as a GFCI)?

The chassis of the product must be connected to ground, to the frame of a vehicle or the ground plate or hull of a boat".
First, it seems clear to me (at least), that the manufacturer saying "ground" implies what we know as "earth" (i.e. the general mass of earth, and/or the "means of earthing" in an installation).

The problem is, this doesn't help you in the slightest, because the manufacturer is giving you the option, covering a very wide range of applications.


The answer for you will, I suppose, depend on what the Outside Broadcast Vehicle is doing, and whether you feel you can ensure safety without providing an external "earth", if you connect to "chassis". This gets more complicated, if the vehicle has to provide power for equipment "off vehicle".

I'd recommend you get hold of BS7909 "Code of practice for temporary electrical systems for entertainment and related purposes" which discusses these kinds of applications, as well as the relevant elements of Part 7 of the Wiring Regulations BS7671, dependent on the intended use of the vehicle (e.g. 711 and 717)


These inverters are used a lot for marine use. I have e-mailed the company about this, but never recieved a reply, maybe they thought it was a stupid question!
Well, I don't think it's a daft question - there is a set of reasonably difficult design decisions to be made here, and potentially documented for evidence in case of a future incident.

Maybe also, need to put something in a "users' manual" for the vehicle - any labelling required etc.???

-------------------------
Eur Ing Graham Kenyon CEng MIET TechIOSH
 26 February 2010 01:12 PM
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Veglen

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Thanks gkenyon,

Are you talking about the requirements of section 717 in BS7671 or have I missed the point you are making all together?

Sorry I don't have any info on BS7909.

I have found some info that might be of interest and may be of some help to the OP.

Installation manual for the Vectron Energy Phoenix Inverter Compact!

Read section 4.3 Connection of AC cabling, Page 7 EN
EN NL FR DE ES Appendi

4.3 Connection of the AC cabling

This is a Safety Class I product (supplied with a protective grounding
terminal).
The neutral wire of the AC output of this inverter is connected to the
chassis.
This is to ensure proper functioning of a GFCI (or RCCB) to be installed in the
AC output of the Inverter.
The chassis of the product must be connected to ground, to the frame (of a vehicle) or the ground plate or hull (of a boat).

Not for the reasons I suggested but, Ohwell!


Hope this helps

V

Sorry gkeyon,

You replied to nigel24 before I got my post in however, I'll let you carry on with your debate as it is getting a little too deep for me and follow with interest.

Regards

Edited: 26 February 2010 at 01:27 PM by Veglen
 26 February 2010 01:41 PM
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gkenyon

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Originally posted by: Veglen

Thanks gkenyon,



Are you talking about the requirements of section 717 in BS7671 or have I missed the point you are making all together?
Yes, 717 should well apply - but does 711 also apply (we don't know full details of the use of the vehicle)? See 711.1 for further details - and indeed this references BS7909 for cases where it does not apply !!!

My guess is, it's only 717 + BS7909: but without full details, can't make a decision.



Sorry I don't have any info on BS7909.
See link in previous post, to info in BSI web-site. For a general read, many local libraries have a "read on-line" subscription to BSI Standards, either from computers at the library, and/or from your home computer over internet using your local library login.



I have found some info that might be of interest and may be of some help to the OP.



Installation manual for the Vectron Energy Phoenix Inverter Compact!



Read section 4.3 Connection of AC cabling, Page 7 EN

EN NL FR DE ES Appendi



4.3 Connection of the AC cabling



This is a Safety Class I product (supplied with a protective grounding

terminal).

The neutral wire of the AC output of this inverter is connected to the

chassis.

This is to ensure proper functioning of a GFCI (or RCCB) to be installed in the

AC output of the Inverter.

The chassis of the product must be connected to ground, to the frame (of a vehicle) or the ground plate or hull (of a boat).

Yes - but really, the manufacturer is letting you make decisions based on the intended use, as I said.

Not for the reasons I suggested but, Ohwell!
No problem, as I said, it's an issue when so many "errors and assumptions" are made when people write the apparently simple terms "earth", "ground", "chassis".

-------------------------
Eur Ing Graham Kenyon CEng MIET TechIOSH
 26 February 2010 02:00 PM
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AJJewsbury

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i presume RCD is the same as a GFCI

yes - Ground Fault Circuit Interrupter (much of the rest of the world have "interrupters" rather than "breakers")

On the continent you tend to see various translations of "differential" instead of "residual", but the meaning's all the same.

- Andy.
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