What crimp for 10mm fly lead to earthing nut ?

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Hi,
I have always used banjos when earthing the armour on an SWA but have now switched to earthing nuts. I am making off a 10mm fly lead to the earthing nut (using 10mm to match the line conductor size as is good practice). Can't find any ring crimps that will take 10mm cable but have a lug hole small off to go on the earthing nut screw. Any ideas where to get one ?
thanks

 

[nicebutdim]

What size of screw is in the earthing nut? Cembre make lugs for 10mm cable with hole from 4mm upwards.

 

[Back to the Light]

What size of screw is in the earthing nut? Cembre make lugs for 10mm cable with hole from 4mm upwards.

Thanks for that I'll try them. Its a 3.5mm screw. I would have thought the main electrical wholesalers would stock them but I guess maybe people don't bother with anything over 6mm for a fly lead.

 

[davesparks]

Is the armour being used as the CPC or is the flylead just there to earth the armour?
If your just earthing the armour then a 6mm would be fine.

The screw in a 20mm earthing nut is M4 and a standard 10x6 lug can be persuaded to sit properly under it.

 

[Back to the Light]

Is the armour being used as the CPC or is the flylead just there to earth the armour?
If your just earthing the armour then a 6mm would be fine.

The screw in a 20mm earthing nut is M4 and a standard 10x6 lug can be persuaded to sit properly under it.

In this case its just for earthing the armour which is not used as the cpc. But the earthing of the armour is required to be able to handle the full fault current and although I'm sure 6mm would be fine a lot of the time if table 54.7 is used (rather than doing the adiabatic calculation) then the fly lead should be the same size as the line conductor so 10mm is the requirement here. I can't think that this is so unusual so I'm surprised that 10mm lugs with small (M4) holes are not widely available.

 

[pc1966]

Is a longer M4 screw and 2 * 6mm in parallel an option using the typical yellow crimps?

Or even a 2nd M4 short screw and using another tapped hole on the earthing nut?

 

[James]

Or use an banjo and m6 screw and nut for the larger cables.
Keep the earthing nuts for small stuff up to 4mm cable.

 

[Back to the Light]

Is a longer M4 screw and 2 * 6mm in parallel an option using the typical yellow crimps?

Or even a 2nd M4 short screw and using another tapped hole on the earthing nut?

Yep..good idea! Unfortunately I'm already tight for space terminating the other end of the fly lead with the two 10mm cpc joining at the same terminal so 2 x 6mm isn't an option in this case

 

[Back to the Light]

Or use an banjo and m6 screw and nut for the larger cables.
Keep the earthing nuts for small stuff up to 4mm cable.

Thanks, I'm going to try Cembre as suggested by NicebutDim but failing that I will revert to a banjo. Still don't know why its so hard to get a 10mm lug with a hole to fit M4 but there you go.....

 

[pc1966]

Still don't know why its so hard to get a 10mm lug with a hole to fit M4 but there you go.....

Well an M4 screw itself can't carry much current compared to 10mm cable, nor can it apply a lot of clamping force to make sure something that stiff stays in place, etc.

 

[James]

4mm diameter is 12.5sq mm
Take a bit off for the thread groove and it is pretty close to 10sq mm

 

[pc1966]

4mm diameter is 12.5sq mm
Take a bit off for the thread groove and it is pretty close to 10sq mm

Yes, but usually steel so closer to 1.2mm^2 copper in terms of conductivity. Less if stainless...

 

[James]

Yes, but usually steel so closer to 1.2mm^2 copper in terms of conductivity. Less if stainless...

Over a distance of 1to 2 mm, I can’t believe the material resistance makes that much difference.
And often the screws are nickel plated brass.

 

[westward10]

The answer to this is by @davesparks in #4, use 6.0 it requires no further thought.

 

[davesparks]

In this case its just for earthing the armour which is not used as the cpc. But the earthing of the armour is required to be able to handle the full fault current and although I'm sure 6mm would be fine a lot of the time if table 54.7 is used (rather than doing the adiabatic calculation) then the fly lead should be the same size as the line conductor so 10mm is the requirement here. I can't think that this is so unusual so I'm surprised that 10mm lugs with small (M4) holes are not widely available.

Are you connecting to the armour at both ends of the cable? If you are then that will be 2x6mm in parallel.

Why not just get a plain lug and drill your own 4mm hole in it?
Lugs are available with pre-made holes in the commonly used sizes, plain lugs exist to fill in the gaps for the other sizes.

 

[davesparks]

Keep the earthing nuts for small stuff up to 4mm cable.

Why? I use earthing nuts for all sizes of SWA gland and haven't had an issue.
They are a lot better in the 32mm and upwards sizes as they have an M8 stud instead of the little screws.

 

[davesparks]

Well an M4 screw itself can't carry much current compared to 10mm cable, nor can it apply a lot of clamping force to make sure something that stiff stays in place, etc.

The screw shouldn't be expected current, it should only be clamping the lug to the brass.

Likewise the terminal screw shouldn't be making sure something stiff stays in place, the regulations require that terminations are not placed under any undue stress. Conductors should be formed (and supported if required) such that the termination isn't under stress.

 

[nicebutdim]

Why? I use earthing nuts for all sizes of SWA gland and haven't had an issue.
They are a lot better in the 32mm and upwards sizes as they have an M8 stud instead of the little screws.

I'd only seen them up to 32mm as that's the largest I'd ever sourced. Recently I learned they're available up to 75mm and that their price is suitably frightening. Then again 300mm 4 core isn't exactly cheap, so cost pales somewhat in that regard.