Tails into metal switch fuse

[Gazthesparky]

I've got a job where I'm running a Swa sub main to a 17th edition board. I've got to put a switchfuse by the meter and I'm intending to run tails from the meter into it.

Previously I've put a male bush and locknut in the bottom and run the tails into that but I'm after other ideas that give strain relief.

I've seen the wiska tails stuffing gland but it's expensive at about 20 quid a pop

Any other ideas ? Suggestions

Cheers

 

[marc8]

I would argue it actually does matter hence the regulation as stated in post 81, consider a fault from phase core to swa then it will return on one of 2 paths which may be the tek screw fixing which may have to withstand 1000's of amps in a pulse before the OCPD hopefully operates, better to isolate that end than to make a poor joint that way you ensure the fault current will travel down the correctly glanded end.

As lee points out any removable glanding plates or metal enclosures which are not one solid contruct require earth tails as you should not rely on the fixing screws.

we have not relied on fixings screws for electrical work we have an earth contact properly glanded on the switch fuse end. inside the trunking until we enter the consumer unit we are double insulated all the way in on both cables. Should i have been able to get a nut & bolt through a banjo in the trunk then i would have considered it as this is what we have on the other end as we don't have room then I have done this, I am not even required to put anything on to the gland in fact I could even omit the gland altogether & just done what most others do & wrap some tape round it.
the point of the post was how to consider bringing cabling into the consumer unit for GN3, I have just pointed out in my previous post how I have done mine & as the regs are open to interpretation & the fact that every year I have proved that I am competent to do my job then I am Happy with it. to the guy/ Girl who first posted good luck & hope anything I have posted with regard to the trunking helps.

 

[Midwest]

? do you not do your boards tight to the ceiling? it looks better than 20 stuffers out of the top.

if i had a fuseboard changed and they did that they would be changing it unless its in a garage then it might be acceptable.

comerical/industrial installs always have a header for the panel or have multiple 2" bushes from header

Blimey, I started something there! Anyhow, this particular occasion the new CU was a replacement in under stairs cupboard, so I couldn't get tight to the ceiling even if I wanted too, not withstanding in new builds, CU should be mounted in accessible position. Done hundreds (slight exagg') of industrial metal trunking & metal enclosures with paxolin. Looks ok there, but not in domestic. Prefer silver locknuts peaking out, rather than brown pax'.

 

[shanky887614]

Blimey, I started something there! Anyhow, this particular occasion the new CU was a replacement in under stairs cupboard, so I couldn't get tight to the ceiling even if I wanted too, not withstanding in new builds, CU should be mounted in accessible position. Done hundreds (slight exagg') of industrial metal trunking & metal enclosures with paxolin. Looks ok there, but not in domestic. Prefer silver locknuts peaking out, rather than brown pax'.

use grommit strip or even the proper flanges

 

[Midwest]

What flanges would that be, I'm thinking horizontal plastic trunking, top entry? Hager Design 30 comes with trunking knockouts for vertical entry.

 

[Darkwood]

we have not relied on fixings screws for electrical work we have an earth contact properly glanded on the switch fuse end. inside the trunking until we enter the consumer unit we are double insulated all the way in on both cables. Should i have been able to get a nut & bolt through a banjo in the trunk then i would have considered it as this is what we have on the other end as we don't have room then I have done this, I am not even required to put anything on to the gland in fact I could even omit the gland altogether & just done what most others do & wrap some tape round it.


the point of the post was how to consider bringing cabling into the consumer unit for GN3, I have just pointed out in my previous post how I have done mine & as the regs are open to interpretation & the fact that every year I have proved that I am competent to do my job then I am Happy with it. to the guy/ Girl who first posted good luck & hope anything I have posted with regard to the trunking helps.

I understand the fact that you have a correctly terminated end and this wasn't the point I was trying to put across, people do forget that the earth path you create may be used by faults non-related to that circuit hence any strapping down of a loose end regardless of whether the other end is sufficiently terminated must be a mechanically and electrically sound joint. It is better to actually not connect it as in this example if you cannot get the correct terminations usually nut and bolt, I'm not saying the actual joint you made would fail but personally I wouldn't be relying on a tek screw to ensure thousands of amps pass through without incident..

Think about similar situe's where the fixings cannot be relied on for earthing paths and you may understand where I'm coming from - bonding straps across trunking joints and earth tails from glands panels etc ...examples of weak point in a fault return path.

 

[Hellmooth]

I understand the fact that you have a correctly terminated end and this wasn't the point I was trying to put across, people do forget that the earth path you create may be used by faults non-related to that circuit hence any strapping down of a loose end regardless of whether the other end is sufficiently terminated must be a mechanically and electrically sound joint. It is better to actually not connect it as in this example if you cannot get the correct terminations usually nut and bolt, I'm not saying the actual joint you made would fail but personally I wouldn't be relying on a tek screw to ensure thousands of amps pass through without incident..

Think about similar situe's where the fixings cannot be relied on for earthing paths and you may understand where I'm coming from - bonding straps across trunking joints and earth tails from glands panels etc ...examples of weak point in a fault return path.

So surely the screws used to attach the board to the wall would fall under the same scope?

 

[Darkwood]

So surely the screws used to attach the board to the wall would fall under the same scope?

They are not been used as a designed fault current route, they are just to hold the board to the wall, the board itself will be suitably earthed 'Hopefully!', if anyone is relying on the wall fixing screws alone to give an earth to the board I think they should apply for a job at McDonalds. :shocked3:

 

[Hellmooth]

And in the OP's case neither is the screws he is using, unless I'm missing something?

 

[davesparks]

And in the OP's case neither is the screws he is using, unless I'm missing something?

He has put a tell screw through a banjo into trunking, creating an earth connection.
As he has pointed out this connection is not strictly necessary, but there is no way of preventing fault current from flowing through it. Fault current will divide proportionally according to the law of resistors in paralell. So under fault conditions there could be significant current flow in that connection, and due to it being a poor connection arcing will occur with the potential for further consequences

 

[Darkwood]

And in the OP's case neither is the screws he is using, unless I'm missing something?

This is not following on from the OP's install this is in relation to post 66 'marc8' where he seems to suggest he has banjo'd a floating end of and swa and tek screwed it into trunking so we are discussing the reliability of such a fixing in regarding to the mentioned regulations.

 

[Midwest]

Or if using the gland plate I normally use piranha nuts these days with an earth connected.

Surely not, with those little bitty grubs screws securing the earth lead, no nut and bolt......bit like a self tapper

 

[Darkwood]

Surely not, with those little bitty grubs screws securing the earth lead, no nut and bolt......bit like a self tapper

A self tapper has a minimal point of contact and by its nature expands the hole as it is screwed in so can easily loose its secureness, a grub, bolt etc as long as they have suitable spring washer or anti vibration washer maintains a larger surface area just by the nature of the male and female threads so not like a self tapper IMHO.

 

[davesparks]

Surely not, with those little bitty grubs screws securing the earth lead, no nut and bolt......bit like a self tapper

The grub screw is just there to lock the nut onto the gland, there is a pan headed screw in a tapped hole for the earth connection.

 

[Midwest]

Still a little bitty screw, and all part of the earth fault & not one you can tighten up with an 'impact driver'. Who started this argument anyway. Back off to manage more manly things, the BBQ

 

[davesparks]

Using an impact driver to tighten a connection is even worse