5.4.6.3 - Where must this connection be made?
5.4.6.3 - Where must this connection be made?
I have some metal framed walls I need to earth as DI is not maintained. I was under the impression I would need to run a PEC from the earth bar but remember someone saying that such connection could be made using the earth's in the cables but this didn't seem right to me so just seeking some guidance on the procedure of doing so as I've never worked with metal frames before.
Re: 5.4.6.3 - Where must this connection be made?
Ok, start with the rule that requires the framing to be connected to the earthing system.
5.4.6.1 requires ALL structural metalwork forming a frame of a structure to be "earthed" .
Just to reinforce the point; this is under the heading of "earthing of equipment"; and not under the heading of "equipotential bonding".
Earthing is principally about the passing of a high fault current, in order to operate a protective device within the required time.
Which is why the clause sets the minimum size of conductor depending on the size of the active conductor(s) that might fault to the framing.
So it's a protective earthing conductor (PEC), not an equipotential bonding conductor (EBC).
Next; 5.5.2 covers how PECs can be connected; and the options are illustrated in Fig 5.3.
Nothing in Fig 5.3 specifically refers to structural metal, but what maters is where the circuit(s) that could possibly fault to the framing riginat.
Which could be different origins for different circuits, even for the same section of framing.
If there is only one circuit, then yes you can simply use the PEC of that circuit.
but where there is more than one circuit, you need to repeat that for every circuit.
Otherwise there's a risk that the circuit that does the earthing
(a) isn't heavy enough , or
(b) gets removed, leaving other circuits in place but no earthing for the frame.
Then there could be a circuit without its own PEC, in which case a separate PEC must be used.
Last possibility is there may be no circuits
Which makes it difficult to work out the minimum size to use; but the requirement to earth the framing has no Exceptions.
After all, a circuit could be added later; when it's difficult to earth the framing.
Best option is always to run a separate PEC; and make it big enough that it covers all circuits eg same size as MEC.
Take it to earth busbar - and label it so it doesn't get disconnected
I only use circuit PECs for local stuff like earthing metal cladding adjacent to eg lights, or metal flush boxes; not for framing.
And I do it at every fitting, because that's where the risk of fault is greatest and future changes can't leave anything not earthed.
The worst is ceiling battens when the rest of the framing is timber; 'cos then you need to earth every run of batten.
There are those who reckon ceiling battens are not "framing", and apply the part of 5.4.6.1 that allows earthing to be omitted provided double insulation is maintained (as for nail plates).
But that's not an argument I believe; and I certainly wouldn't want to stand in Coroner's Court arguing that.
5.4.6.1 requires ALL structural metalwork forming a frame of a structure to be "earthed" .
Just to reinforce the point; this is under the heading of "earthing of equipment"; and not under the heading of "equipotential bonding".
Earthing is principally about the passing of a high fault current, in order to operate a protective device within the required time.
Which is why the clause sets the minimum size of conductor depending on the size of the active conductor(s) that might fault to the framing.
So it's a protective earthing conductor (PEC), not an equipotential bonding conductor (EBC).
Next; 5.5.2 covers how PECs can be connected; and the options are illustrated in Fig 5.3.
Nothing in Fig 5.3 specifically refers to structural metal, but what maters is where the circuit(s) that could possibly fault to the framing riginat.
Which could be different origins for different circuits, even for the same section of framing.
If there is only one circuit, then yes you can simply use the PEC of that circuit.
but where there is more than one circuit, you need to repeat that for every circuit.
Otherwise there's a risk that the circuit that does the earthing
(a) isn't heavy enough , or
(b) gets removed, leaving other circuits in place but no earthing for the frame.
Then there could be a circuit without its own PEC, in which case a separate PEC must be used.
Last possibility is there may be no circuits
Which makes it difficult to work out the minimum size to use; but the requirement to earth the framing has no Exceptions.
After all, a circuit could be added later; when it's difficult to earth the framing.
Best option is always to run a separate PEC; and make it big enough that it covers all circuits eg same size as MEC.
Take it to earth busbar - and label it so it doesn't get disconnected
I only use circuit PECs for local stuff like earthing metal cladding adjacent to eg lights, or metal flush boxes; not for framing.
And I do it at every fitting, because that's where the risk of fault is greatest and future changes can't leave anything not earthed.
The worst is ceiling battens when the rest of the framing is timber; 'cos then you need to earth every run of batten.
There are those who reckon ceiling battens are not "framing", and apply the part of 5.4.6.1 that allows earthing to be omitted provided double insulation is maintained (as for nail plates).
But that's not an argument I believe; and I certainly wouldn't want to stand in Coroner's Court arguing that.
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Re: 5.4.6.3 - Where must this connection be made?
"5.4.6.1 requires ALL structural metalwork forming a frame of a structure to be "earthed" .
Just to reinforce the point; this is under the heading of "earthing of equipment"; and not under the heading of "equipotential bonding"."
I assume you're more referring to 5.4.6.2 in this statement? My situation is in a non-domestic situation so 5.4.6.2 doesn't apply, the only reason I believe earthing is required is as said above due to lack of maintaining DI at flush boxes etc (unless there are good ways to keep such connections enclosed)
Totally understand it's earthing and needs to be sized to the largest active conductor that poses a risk, in my case that's 2.5mm2 so I'll be using a 2.5mm2 earth
I think the thing that throws me off taking it directly to the PEC of the circuit is 5.5.2.2.1 and I thought the whole reason of this rule was to prevent the things you mentioned above like "(b) gets removed, leaving other circuits in place but no earthing for the frame."
I read 5.5.2.2.1 as the PEC in the same cable sheath can only be used to earth equipment supplied from the circuit, since the metal frame isn't equipment supplied from the circuit I figured this meant using such PEC wasn't permitted and the only option was to run a dedicated PEC from earth bar to the metalwork and ensure that any part of the metalwork measured less than 0.5 ohm back to the earth bar in accordance with 5.4.6.3
Just to reinforce the point; this is under the heading of "earthing of equipment"; and not under the heading of "equipotential bonding"."
I assume you're more referring to 5.4.6.2 in this statement? My situation is in a non-domestic situation so 5.4.6.2 doesn't apply, the only reason I believe earthing is required is as said above due to lack of maintaining DI at flush boxes etc (unless there are good ways to keep such connections enclosed)
Totally understand it's earthing and needs to be sized to the largest active conductor that poses a risk, in my case that's 2.5mm2 so I'll be using a 2.5mm2 earth
I think the thing that throws me off taking it directly to the PEC of the circuit is 5.5.2.2.1 and I thought the whole reason of this rule was to prevent the things you mentioned above like "(b) gets removed, leaving other circuits in place but no earthing for the frame."
I read 5.5.2.2.1 as the PEC in the same cable sheath can only be used to earth equipment supplied from the circuit, since the metal frame isn't equipment supplied from the circuit I figured this meant using such PEC wasn't permitted and the only option was to run a dedicated PEC from earth bar to the metalwork and ensure that any part of the metalwork measured less than 0.5 ohm back to the earth bar in accordance with 5.4.6.3
Re: 5.4.6.3 - Where must this connection be made?
Interesting guys, so are we saying that rondo battens are part of the building framing, as there is another post on this forum under earthing and bonding that is is suggested it is possibly part of the mounting system?
It would be nice to clarify what rondo battens are classified as possibly?
It would be nice to clarify what rondo battens are classified as possibly?
Re: 5.4.6.3 - Where must this connection be made?
No, when I said 5.4.6.1 I meant 5.4.6.1; but I was quoting 2018 edition; which has slightly different wording and clause structure.
And the changes were made for good reason; so it makes sense to look at those requirements even though they haven't yet been mandated by ESRs.
applying 2007+A1+A2 (as currently cited by ESRs):
correct 5.4.6.2 won't apply, being non-domestic.
Correct that if DI can't be maintained, the "conductive building materials" must be earthed.
The clause applies to "structural metalwork", but then specifically includes all conductive building materials under that heading, and so applies the same rule to both types of metalwork.
The 2018 version makes the original intent clearer, by treating structural metalwork" & "other conductive building materials" slightly differently.
This removes the "excuse" of not earthing structural steels framing because of DI.
Typical metal-framed partitions have top & bottom plates that effectively tie all the studs together, so 5.4.6.3 allows a single connection as minimum.
However if you have several circuits involved that should be a single connection per circuit, at the first location of each circuit where risk of contact / loss of DI arises. Better would be earthing at each location.
Alternatively, there are (options (A) & (B) for preventing contact, eg box liners, plastic boxes, tying the conductors, etc; but it's likely to be quicker & cheaper to just make an earth connection than to take effective measures.
The other thing about steel studs is that while some brands have a "rolled" edge on the apertures, others have sharp edges, meaning every time a cable passes through it needs to be protected from mechanical damage.
The wording of 5.5.2.2.1 is intended to prohibit using one circuit's PEC to earth equipment supplied by another circuit. Eg adding a luminaire / ltg point that requires a PEC when the ltg ct doesn't have one; you can't earth the new fitting / point to another nearby circuit.
I don't believe it was meant to prohibit use of a circuit PEC to earth "extraneous conductive parts" in close proximity to that circuit.
Certainly doesn't apply that way to a flush box, because a flush box or other mounting accessory is "electrical equipment" [1.4.46]. See also 5.5.1
And if you earth the box (and bush the cable apertures in the framing as required), then the framing isn't liable to become alive.
So if the only risk of the framing becoming live is the circuits to points on the framing; then there's no need for a separate PEC .
But if there is some other possible source of livening, eg a cable just passing through to somewhere else; then a separate PEC may be needed.
Some would view simple, non-load-bearing partition walls as non-structural; but using ordinary dictionary definitions they are part of the structure even if only dividing one space from another. Same applies to ceiling battens. Another example is "T-bar" framing for suspended ceilings (often with "troffer" luminaires sitting on them, and nothing but air between the 'internal' electrical parts and the T-bar.
With "Rondo" & similar battens, current rules require earthing of DI not maintained[ 5.4.6.1]; but they also require the 'frame' of a dwelling to be earthed [5.4.6.2]. Arguing about whether it's "frame" is a fairly pointless exercise, each of us has to decide for ourselves. But if it comes to Court (or EWRB); Oxford dictionary says that "frame" means: "the rigid supporting structure of a vehicle, piece of furniture, or other object". And if you look at the Building Code; I think you'll find it's under the heading of "framing".
And the changes were made for good reason; so it makes sense to look at those requirements even though they haven't yet been mandated by ESRs.
applying 2007+A1+A2 (as currently cited by ESRs):
correct 5.4.6.2 won't apply, being non-domestic.
Correct that if DI can't be maintained, the "conductive building materials" must be earthed.
The clause applies to "structural metalwork", but then specifically includes all conductive building materials under that heading, and so applies the same rule to both types of metalwork.
The 2018 version makes the original intent clearer, by treating structural metalwork" & "other conductive building materials" slightly differently.
This removes the "excuse" of not earthing structural steels framing because of DI.
Typical metal-framed partitions have top & bottom plates that effectively tie all the studs together, so 5.4.6.3 allows a single connection as minimum.
However if you have several circuits involved that should be a single connection per circuit, at the first location of each circuit where risk of contact / loss of DI arises. Better would be earthing at each location.
Alternatively, there are (options (A) & (B) for preventing contact, eg box liners, plastic boxes, tying the conductors, etc; but it's likely to be quicker & cheaper to just make an earth connection than to take effective measures.
The other thing about steel studs is that while some brands have a "rolled" edge on the apertures, others have sharp edges, meaning every time a cable passes through it needs to be protected from mechanical damage.
The wording of 5.5.2.2.1 is intended to prohibit using one circuit's PEC to earth equipment supplied by another circuit. Eg adding a luminaire / ltg point that requires a PEC when the ltg ct doesn't have one; you can't earth the new fitting / point to another nearby circuit.
I don't believe it was meant to prohibit use of a circuit PEC to earth "extraneous conductive parts" in close proximity to that circuit.
Certainly doesn't apply that way to a flush box, because a flush box or other mounting accessory is "electrical equipment" [1.4.46]. See also 5.5.1
And if you earth the box (and bush the cable apertures in the framing as required), then the framing isn't liable to become alive.
So if the only risk of the framing becoming live is the circuits to points on the framing; then there's no need for a separate PEC .
But if there is some other possible source of livening, eg a cable just passing through to somewhere else; then a separate PEC may be needed.
Some would view simple, non-load-bearing partition walls as non-structural; but using ordinary dictionary definitions they are part of the structure even if only dividing one space from another. Same applies to ceiling battens. Another example is "T-bar" framing for suspended ceilings (often with "troffer" luminaires sitting on them, and nothing but air between the 'internal' electrical parts and the T-bar.
With "Rondo" & similar battens, current rules require earthing of DI not maintained[ 5.4.6.1]; but they also require the 'frame' of a dwelling to be earthed [5.4.6.2]. Arguing about whether it's "frame" is a fairly pointless exercise, each of us has to decide for ourselves. But if it comes to Court (or EWRB); Oxford dictionary says that "frame" means: "the rigid supporting structure of a vehicle, piece of furniture, or other object". And if you look at the Building Code; I think you'll find it's under the heading of "framing".
Re: 5.4.6.3 - Where must this connection be made?
So an steel RSJ beam within a wooden framed building needs to be earthed ?
Re: 5.4.6.3 - Where must this connection be made?
Under currently-cited requirements:
in domestic: yes . Because it's structural metalwork that's part of the frame
In other installations; maybe; depending on whether DI is maintained.
Other installations changes to "yes, always" in 2018 edition; again because it's structural / frame.
And if the steel frame is in contact with ground, it needs to be bonded under 5.6 even if it doesn't need to be earthed under 5.4.
in domestic: yes . Because it's structural metalwork that's part of the frame
In other installations; maybe; depending on whether DI is maintained.
Other installations changes to "yes, always" in 2018 edition; again because it's structural / frame.
And if the steel frame is in contact with ground, it needs to be bonded under 5.6 even if it doesn't need to be earthed under 5.4.
Re: 5.4.6.3 - Where must this connection be made?
Interesting, I'll will have a look through, appreciate the information as always
Looks like this has been a good topic to get people talking, been a big stagnant here as of late
Looks like this has been a good topic to get people talking, been a big stagnant here as of late