Was having a discussion with another electrician regarding earthing a stainless steel bench top.
He advised the bench-top has no electrical fittings mounted on it. Apparently outlets are mounted above the bench top.
My understanding for this type of scenario, there is no requirement for earthing, and the relevant clause in 3000 would be 5.4.6.1. (bench-top to be considered ‘conductive building materials’).?
There wouldn’t be a requirement for ‘bonding’ assuming there is no metallic pipe work connecting the bench-top to the mass of earth. Any pipe work would be PVC.
Does this sound correct? I’m sure this has been brought up before. Thanks.
Steel bench top.
Re: Steel bench top.
protective earthing [5.2.1] is not required.
the bench is not any of the things that is required to be earthed for fault protection by automatic disconnection of supply [5.4]
It's not exposed conductive parts of electrical equipment [5.4.1.1], nor conductive building materials [5.4.1.2] . Even if it's built in as against free-standing; it's fixtures & fittings and not part of the building.
It's certainly not "structural metalwork" ; so 5.4.6 doesn't apply either - though that clause does provide guidance that can be applied more widely when considering the need to earth.
And while many years ago the was a "requirement" (in ECP 25) to equipotentially bond such benches ; it was never justified.
(and complying with that ECP was never mandatory anyway - need to go back to 1976 Regs for an enforceable requirement).
There's nothing to suggest this bench could ever be either livened or dragged up to a higher potential that the installation's earthing system by any conceivable single-fault condition.
So bonding [5.6] isn't required either.
the bench is not any of the things that is required to be earthed for fault protection by automatic disconnection of supply [5.4]
It's not exposed conductive parts of electrical equipment [5.4.1.1], nor conductive building materials [5.4.1.2] . Even if it's built in as against free-standing; it's fixtures & fittings and not part of the building.
It's certainly not "structural metalwork" ; so 5.4.6 doesn't apply either - though that clause does provide guidance that can be applied more widely when considering the need to earth.
And while many years ago the was a "requirement" (in ECP 25) to equipotentially bond such benches ; it was never justified.
(and complying with that ECP was never mandatory anyway - need to go back to 1976 Regs for an enforceable requirement).
There's nothing to suggest this bench could ever be either livened or dragged up to a higher potential that the installation's earthing system by any conceivable single-fault condition.
So bonding [5.6] isn't required either.
- Rating: 33.33%
Re: Steel bench top.
Thanks Aleck.
Yes I didn’t think clause 5.4.6 seemed quite the right fit for a steel bench top. There just doesn’t seem to be an appropriate clause for something like this. I presume if electrical fittings were to be fitted on a steel splash back for example, there would be a requirement to earth the splash back? If so there must be some directive from 3000..?
Yes I didn’t think clause 5.4.6 seemed quite the right fit for a steel bench top. There just doesn’t seem to be an appropriate clause for something like this. I presume if electrical fittings were to be fitted on a steel splash back for example, there would be a requirement to earth the splash back? If so there must be some directive from 3000..?
-
Mazdaman
- Posts: 22
- Joined: Tue Apr 14, 2020 12:00 pm
- Location: Canterbury
- Has thanked: 57 times
- Been thanked: 5 times
Re: Steel bench top.
This document from ECANZ FAQ may help as well: Q12012_Bonding-of-sinks-and-exposed-metal-work.
- Attachments
-
- Q12012_Bonding-of-sinks-and-exposed-metal-work.pdf
- (105.86 KiB) Downloaded 673 times
- Rating: 16.67%
Re: Steel bench top.
Yes, if electrical fittings are mounted to a conductive surface (benchtop , splashback , wall lining, ceiling, foil-backed plaster-board, whatever); then the conductive material may need to be earthed.
But note that there's a difference between "structural metalwork" and "conductive building materials".
5.4.1.2 says CBM must be earthed i.a.w 5.4.6.
5.4.6 has the title "structural metalwork including CBM"
Which suggests to some people that all CBM is structural; when clearly that's not true. In reality the meaning is that the clause includes requirements for both. Reversing it, to say "CBM, including structural metalwork" would have been more accurate - and unlikely to mislead.
Under 5.4.6.1; para 1 sets two "trigger" conditions: risk of contact with live parts, or DI not fully maintained.
If either condition exists ; then earthing is required.
Then para 2 sets another, separate, requirement about what might happen if a conductor breaks at a termination; along with some recognised methods of dealing with those issues. Note that earthing the metal concerned also effectively deals with para 2.
But "earth if either condition is met" doesn't mean earthing is only required if one (or both) of the 'trigger" conditions exists; because 5.4.6.2 says that in domestic installations "structural metalwork forming the frame of a dwelling" must always be earthed; regardless of any other considerations.
So for non-domestic we have a reasonably straightforward set of rules for deciding whether or not earthing of is required.
But when we're in domestic, we need to distinguish between the two types;
and if the item in question is structural metal, we then need to decide whether or not it is part of the frame of a dwelling.
I can't imagine a bench-top would ever be classed as structural metalwork; let alone part of the frame of a dwelling.
But if it had electrical fittings mounted to it then I would certainly treat it as "conductive building materials"; and apply 5.4.6.1.
(So I must withdraw my statement yesterday that a bench is not CBM.)
Applying 5.4.6.1; mounting an accessory (eg switch or socket ) flushed into the metal would be likely to involve at least one of the "trigger" conditions; and therefore require earthing. Surface mounting, using a DI mounting might well not require earthing.
--------
Some of the other things that need to be thought about in this context include:
- metal wall & roof cladding
- tee-bars of suspended ceilings (especially if "troffer" lights are used)
- "rondo" & similar metal ceiling battens
- gang nail plates
- metal flush boxes / mounting plates
But any discussion WRT these other types of metal would be better under their own forum thread
But note that there's a difference between "structural metalwork" and "conductive building materials".
5.4.1.2 says CBM must be earthed i.a.w 5.4.6.
5.4.6 has the title "structural metalwork including CBM"
Which suggests to some people that all CBM is structural; when clearly that's not true. In reality the meaning is that the clause includes requirements for both. Reversing it, to say "CBM, including structural metalwork" would have been more accurate - and unlikely to mislead.
Under 5.4.6.1; para 1 sets two "trigger" conditions: risk of contact with live parts, or DI not fully maintained.
If either condition exists ; then earthing is required.
Then para 2 sets another, separate, requirement about what might happen if a conductor breaks at a termination; along with some recognised methods of dealing with those issues. Note that earthing the metal concerned also effectively deals with para 2.
But "earth if either condition is met" doesn't mean earthing is only required if one (or both) of the 'trigger" conditions exists; because 5.4.6.2 says that in domestic installations "structural metalwork forming the frame of a dwelling" must always be earthed; regardless of any other considerations.
So for non-domestic we have a reasonably straightforward set of rules for deciding whether or not earthing of is required.
But when we're in domestic, we need to distinguish between the two types;
and if the item in question is structural metal, we then need to decide whether or not it is part of the frame of a dwelling.
I can't imagine a bench-top would ever be classed as structural metalwork; let alone part of the frame of a dwelling.
But if it had electrical fittings mounted to it then I would certainly treat it as "conductive building materials"; and apply 5.4.6.1.
(So I must withdraw my statement yesterday that a bench is not CBM.)
Applying 5.4.6.1; mounting an accessory (eg switch or socket ) flushed into the metal would be likely to involve at least one of the "trigger" conditions; and therefore require earthing. Surface mounting, using a DI mounting might well not require earthing.
--------
Some of the other things that need to be thought about in this context include:
- metal wall & roof cladding
- tee-bars of suspended ceilings (especially if "troffer" lights are used)
- "rondo" & similar metal ceiling battens
- gang nail plates
- metal flush boxes / mounting plates
But any discussion WRT these other types of metal would be better under their own forum thread
Re: Steel bench top.
I was just going to make comments on the "not conductive building materials" but seems you've already cleared it up
I simply believe the only clause that applies to metal bench tops is 5.4.6.1 and that the trigger conditions for said earthing is , in simple terms lack of double insulation, as said
I simply believe the only clause that applies to metal bench tops is 5.4.6.1 and that the trigger conditions for said earthing is , in simple terms lack of double insulation, as said
Re: Steel bench top.
Unfortunely, the document from ECANZ FAQ: Q12012_Bonding-of-sinks-and-exposed-metal-work is NOT fully correct.
The key words “equipotential bonding” and the large contribution it makes to the electrical safety in the specified conditions, when multiple metallic water supply pipes, taps and drain metalwork contained to the waste pipe are present, that equipotential bonding gives is missing.
These missing details are broadly obtained are explained in AS/NZS 3000:2007 definition clause 1.4.52 details the required outcomes and function of equipotential bonding. In AS/NZS 3000:2018 the clause is 1.4.60.
AS/NZS 3000:2007 or AS/NZS 3000:2018 clause 5.6.2.5 in Note 1 gives some further details of the outcomes provided by “equipotential bonding”.
The key words “equipotential bonding” and the large contribution it makes to the electrical safety in the specified conditions, when multiple metallic water supply pipes, taps and drain metalwork contained to the waste pipe are present, that equipotential bonding gives is missing.
These missing details are broadly obtained are explained in AS/NZS 3000:2007 definition clause 1.4.52 details the required outcomes and function of equipotential bonding. In AS/NZS 3000:2018 the clause is 1.4.60.
AS/NZS 3000:2007 or AS/NZS 3000:2018 clause 5.6.2.5 in Note 1 gives some further details of the outcomes provided by “equipotential bonding”.
Re: Steel bench top.
this OP didn't ask for an explanation of equipotential bonding in general.
He just wanted clarification as to whether either earthing or bonding was required in a particular case; and whether he had correctly identified and understood the relevant requirements
Nor did the ECANZ FAQ try to provide an overview; it only answers the question posed.
I think it does that well enough.
pluto hasn't identified anything in that answer that's actually wrong;
and he's incorrect to say the ECANZ FAQ doesn't include the full term "equipotential bonding".
Yes, there's a definition, and yes there's more info available.
But neither the definition, nor the other info, relates directly to answering either this thread's original question or the slightly different one that ECANZ answered.
Both questions are about whether either earthing or bonding are required in a particular circumstance.
And the answers are, quite simply, that for benches bonding is not required (despite having once been mandatory), but earthing is sometimes required.
He just wanted clarification as to whether either earthing or bonding was required in a particular case; and whether he had correctly identified and understood the relevant requirements
Nor did the ECANZ FAQ try to provide an overview; it only answers the question posed.
I think it does that well enough.
pluto hasn't identified anything in that answer that's actually wrong;
and he's incorrect to say the ECANZ FAQ doesn't include the full term "equipotential bonding".
Yes, there's a definition, and yes there's more info available.
But neither the definition, nor the other info, relates directly to answering either this thread's original question or the slightly different one that ECANZ answered.
Both questions are about whether either earthing or bonding are required in a particular circumstance.
And the answers are, quite simply, that for benches bonding is not required (despite having once been mandatory), but earthing is sometimes required.
Re: Steel bench top.
Dare i ask a stupid question . If i decide to earth a stainless sink can I earth to the earth peg , or does it have to go back to the board ?
Re: Steel bench top.
Clause 5.5.2.1 covers where PECs can be connected to.
Connection to the earth electrode is NOT compliant
Clause 5.6.2.2 covers connection of EBC for a water pipe.
Connection to earth electrode is not compliant;
however Note 1 advises that the EBP in this case(water pipe) can be an extension of the MEC - which of course IS connected directly to the electrode.
Technically that's the same as connecting the EBC to the MEC, which is allowed.
Bonding for pools & associated equipment [5.6.2.6] must be to either the subcircuit9s0 supplying pool equipment; or the switchboard those subcircuits originate at.
Other bonding clauses are less specific; however intention is pretty clear:
Basically the ONLY thing we can connect directly to the electrode is the MEC.
PECs and EBCs should be connected to earth bar at swbd, but may be connected to MEC.
Connection to the earth electrode is NOT compliant
Clause 5.6.2.2 covers connection of EBC for a water pipe.
Connection to earth electrode is not compliant;
however Note 1 advises that the EBP in this case(water pipe) can be an extension of the MEC - which of course IS connected directly to the electrode.
Technically that's the same as connecting the EBC to the MEC, which is allowed.
Bonding for pools & associated equipment [5.6.2.6] must be to either the subcircuit9s0 supplying pool equipment; or the switchboard those subcircuits originate at.
Other bonding clauses are less specific; however intention is pretty clear:
Basically the ONLY thing we can connect directly to the electrode is the MEC.
PECs and EBCs should be connected to earth bar at swbd, but may be connected to MEC.
Re: Steel bench top.
Thanks . So if i decided to connect to the MEC at any point along the MEC conductor it would be compliant ?
Re: Steel bench top.
Provided it's connected in a way that doesn't adversely affect the integrity of the MEC.
And remember any work on the MEC is "mains work".
which means any alteration to the MEC is high risk PEW and requires inspection
And remember any work on the MEC is "mains work".
which means any alteration to the MEC is high risk PEW and requires inspection
- Rating: 33.33%
Re: Steel bench top.
Attaching a PEC or bonding conductor to the MEC as you suggest "in a way that doesn't adversely affect the integrity of the MEC" - such as by using a line tap, surely can't be considered "work on main earthing systems"?
I think if you asked an inspector to inspect the connection of a PEC to the MEC as "mains work", they would probably just laugh at you.
I think if you asked an inspector to inspect the connection of a PEC to the MEC as "mains work", they would probably just laugh at you.
- Rating: 33.33%
Re: Steel bench top.
Not what I was getting at, Doug.
Using a line tap couldn't reasonable be considered an alteration to the MEC. (except maybe by EWRB!)
Even cutting & joining would be maintenance rather than alteration. (equivalent to replacing a mains entry box?)
But re-routing the EMEC to achieve the join is an alteration.
EVERY time we work on a main earthing system we need to remember that it's mains work; and consider whether what we do to mit could reasonably be seen as an alteration.
Using a line tap couldn't reasonable be considered an alteration to the MEC. (except maybe by EWRB!)
Even cutting & joining would be maintenance rather than alteration. (equivalent to replacing a mains entry box?)
But re-routing the EMEC to achieve the join is an alteration.
EVERY time we work on a main earthing system we need to remember that it's mains work; and consider whether what we do to mit could reasonably be seen as an alteration.
- Rating: 33.33%