25mm SWA for tails chased in wall

[captaincaveman]

Hiya.

I suspect I already know the answer to this but I would welcome any opinion from anyone who's tried it...
Moving a domestic consumer unit 2M up a wall. Ideally I don't want to use trunking. Debating whether I could get away with 25mm SWA chased into the wall but I don't recall using 25mm SWA and although on paper it can be done (with 7mm left for plaster) I am doubtful I can get/bend the inner cores into the rear access hole of the ccu.
Does anyone reckon I could or am I in the land of fairies?

 

[pc1966]

You would need to gland the armour to earth properly at least on one end anyway, ideally both.

Either way it is going to be hard to bend it in that sort of a spacing.

You might have more luck with some 25mm conduit and 25mm^2 tri-rated cable (ferruled at the ends, naturally) with the CPC run alongside the conduit (as it does not need protection against being nailed from a shock point of view) or in some additional conduit along side (steel or plastic, so it can be pulled). Obviously both L&N must run in the same conduit due to eddy currents.

 

[Risteard]

You would need to gland the armour to earth properly at least on one end anyway, ideally both.

Either way it is going to be hard to bend it in that sort of a spacing.

You might have more luck with some conduit and 25mm tri-rated cable (ferruled at the ends, naturally) with the CPC run alongside the conduit (as it does not need protection against being nailed from a shock point of view) or in some additional conduit along side (steel or plastic, so it can be pulled). Obviously both L&N must run in the same conduit due to eddy currents.

Protective conductors are also required to enter ferromagnetic enclosures in the same entry as the live conductors, so it shouldn't be run separately from them.

 

[pc1966]

Protective conductors are also required to enter ferromagnetic enclosures in the same entry as the live conductors, so it shouldn't be run separately from them.

Really, why?
They don't normally carry current, and when they do it is (or should not be!) long enough to heat via eddy current losses.
Often the CPC is bonded to the outside of some steel enclosure far from the entry point.

 

[Risteard]

Really, why?
They don't normally carry current, and when they do it is (or should not be!) long enough to heat via eddy current losses.
Often the CPC is bonded to the outside of some steel enclosure far from the entry point.

It's a long-standing requirement of BS7671.

 

[telectrix]

you could use "normal" tails in 40 x 16 trunking, but sink the trunking into the wall so that just the lid is proud.

 

[telectrix]

It's a long-standing requirement of BS7671.

what if the CPC enters into the enclosure with a plastic gland?

 

[captaincaveman]

Either way it is going to be hard to bend it in that sort of a spacing.

Hard or impossible? I like a challenge ?

 

[captaincaveman]

Earthing SWA wouldn't be an issue as I would intend to do it in the supply cupboard via a smaller enclosure (some --- has put the meter in the middle of the backing board leaving no room for a ccu ?).
I agree the earth has to be with the L & N.
The owners don't want anything unsightly such as a trunking lid (I wouldn't either to be honest).
I think I might have a walk to Denmans and have a play with some swa to decide (though I suspect they won't let me due to this damn Covid arhhh!)

Talking of which, is anyone else finding customers are refusing to mask up when talking to you? The last 3 I've had haven't done - despite me requesting. Driving me CRAZY ?

 

[pc1966]

521.5.1 mentions this, though oddly only talks about additional CPC in parallel with SWA being permitted to enter separately, not in parallel with conduit which is essentially the same thing (earthed ferromagnetic surround to the live conductors, and possibly also a CPC).

 

[pc1966]

Could you use steel capping over oval trunking for something like tri-rated or flexible (Doncaster 19-stranded) tails?

 

[captaincaveman]

I think I might have an easier solution ?
The meter doesn't have a seal on it so I might move the meter (shush!) to where the wylex is, remove the rest of the junk and then hopefully fit a box on the right hand side..
Why are the metallic ccu's bigger than the plastic ones? I thought things were meant to get smaller in time ?

 

[pc1966]

That is a pretty messy set-up.

Yes, the old Wylex rewirable boxes are really compact, but that presents a problem now for any upgrades after it is boxed in and mic crap fitted along side it.

 

[telectrix]

just take the meter out. it serves no useful purpose. ????

 

[snowhead]

Looks like the Seal Faries have cleaned the place out.

 

[captaincaveman]

Looks like the Seal Faries have cleaned the place out.

The DNO had to replace the MET and he left the cut out and meter unsealed and a couple of spare seals for me (although I have my own anyway). I guess he/she had some common sense ?

 

[Midwest]

Wot about some 3mm steel plate, covered by some plasterboard, or sunk deep enough with some plaster steel mesh.

 

[hasel5]

Why does he want it moved up the wall?

 

[freddo]

2H16 is much more compact and easier to handle/chase in.

 

[Dave OCD]

That would be far too nice to hide in the wall Freddo, I'd strip the pvc sheathing off, polish it and fix with bare p clips and brass slotted roundheads. ?

 

[captaincaveman]

Why does he want it moved up the wall?

Because it's hobby of mine! Lol, Just joking Hasal. It's a rewire. And if you can fit an 8 way + SPD CCU into the 230 x 250mm space the old wylex is in then please, please give me your secret lol!

I'm going to look at it again when I go back to do the rewire. I see 3 options:
1) move the meter (sush)
2) chase into the wall
3) Use trunking

If I decide on chasing I'll consider 2H16 Freddo ?
Other than using a metal trunking lid where can you get a steel plate from?

 

[Midwest]

Other than using a metal trunking lid where can you get a steel plate from?

You can get some pre-made steel plate, @Leesparkykent has a link. I got some 100m wide flat plate, made up by a local steel fabricator with fixing holes & painted, to protect a gas pipe.