SWA cleats

[lazygit]

Hi Guys,
I have come across a couple of SWA cables where the cleats for both are secured by 1 long screw, so that 1 cable is sitting in front of another.
It looks like it has been done because space is limited, and 1 cable cannot go above or below the other.
The grouping factor is not a problem, but I am unsure about the erection method.
It seems secure but I am not sure if this allowed and would like some opinions please.

Many thanks

 

[Lectrician]

Seen it done a couple times, and aslong as it is secure and set-fast, I dont see a problem.

Often done using 'frame type' fixings and a penny washer.

 

[securespark]

Don't know about SWA, but NIC frown upon T&E being clipped like that.

Not that I'm the worlds's biggest NIC fan......

 

[Lectrician]

T+E clipped like that is a tad different! to be honest, SWA like that will dissipate heat far better than stacked ontop!

Ever used cable hangers?

 

[lazygit]

Thanks for the replies.
I remember the T+E issue coming up during my 2391 practical exam.
The problem was that the T+E cables were placed sideways and secured with a clip designed for one cable.
I can understand this being an issue as the T+E cables will get crushed by the clip.
With the SWA cleats there does not seem to be any extra pressure on the cables, and they do seem very secure.
I didnt want to raise an issue untill I was sure there was one
regards

 

[industryspark]

Not a problem at all, have done this myself before..... beats drilling twice as many holes and usefull if as you say space is limited. Dont think grouping factors would be much of a concern either to be honest.

very different from the twin and earth situation.

 

[GaryMo]

Dont think grouping factors would be much of a concern either to be honest.

Have you looked at table 4C1 and the notes below it?

 

[industryspark]

yes, well aware of it..... what i meant was that whilst yes it should be confirmed by reffering to said tables, 90% of the time i have seen this done with 2 cables running side by side, it wouldnt have 'changed' anything.

 

[GaryMo]

Which leads me to wonder if grouping factors are ever applied correctly.

Moving away for a minute, I see loads of installs with pvc single cables in trunking (tens of circuits) yet no apparent derating for grouping.
Is this something most electricians just choose to ignore?

 

[jason1958]

> The problem was that the T+E cables were placed sideways
> and secured with a clip designed for one cable. I can understand
> this being an issue as the T+E cables will get crushed by the clip.

On the surface...
o Big FTE clip over 2 cables - nasty, easy to crush a cable
o Correct P clip over 2 cables - can at least be sized ok
o Double cleat over 2 cables - they exist for SWA & FTE

Been a long time since I saw double-cleats actually.

Under plaster...
o Correct P clip over 2 cables - ok
o Fischer single-hook, double-hook, spring-arm - better!

That can ensure the correct Cg spacing when many cables are present.


Under plaster I often use slightly oversized P-clips which have a "roll inside" to stop the cable slipping out near the screw. Not seen them for years, novel design.

These days I suspect Fischer would be more preferable - they dispense with the need for a screw & rawlplug, they just loop-over & push in. Screwfix website has some, there is a much larger variety though.

 

[jason1958]

Or maybe not then...
Screwfix now only list the various fisher cable clips (hoops, single hook, double hook, boom) in a kit circa £25 rather than each type individually.

Looks like there is not enough uptake so they vanish.

 

[industryspark]

garymo wrote

Which leads me to wonder if grouping factors are ever applied correctly.

Moving away for a minute, I see loads of installs with pvc single cables in trunking (tens of circuits) yet no apparent derating for grouping.
Is this something most electricians just choose to ignore?

personally i think this is common place, i too see lots of installs with swa's on tray with no derating and like you, pvc singles absolutelly crammed into trunking-not just old installs either but new. me personally i always calculate derating factors unless i already know the outcome!

imo when you come across an install where derating hasnt been applied, you should form an opinion. there are lots of examples where i currently work, of cables in trunking what wouldnt stand a chance of ever conforming to grouping factors. Due to the intermittent nature of the circuit loading however i can say that its very unlikelly it will ever be an issue and i would find it hard to argue for it to be put correct bearing in mind downtime and cost.

 

[ColJack]

with 2 cleats on 1 screw, the cables wouldn't actually be touching.. there would be a 6-10mm gap where the cleats meet..

 

[GaryMo]

Read Note 2 under table 4C1, it mentions no grouping factors applied if the horizontal clearance between adjacent cables exceeds twice their overall diameter.
6-10mm is negligible in that circumstance.