SWA too short !

[user786786]

Hi
Fitting a consumer unit in garage . Unfortunately the 16MM SWA is too short to reach consumer unit
So i have done as follows .

Glanded SWA into a metal adaptable box .
earthing nut earthed with 10mm crimped and run to earth block .
2 cores of SWA Brown and Grey ( oversleeved BLUE) run to single pole Henley blocks
25mm LIVE and Neutral tails to consumer Unit main switch through Same 32 mm hole
3rd core of SWA ( oversleeved earth ) to earthing Block in consumer unit .

Everything is being boxed over ( acessable ) so the single insulated cores of SWA will be covered.

Does this seem ok?

Also at the supply end is it okay 25mm tails from henley to 100amp double isolator to feed swa after glanding in a adaptable box .
Thanks

 

[user786786]

I've always stripped the outer sheath off of any scrap 25mm2 or 35mm2 tails and kept it for this purpose.

thats a good idea ?

 

[user786786]

Also not clear is there is overload protection depending on which end the henleys are.

henley will be both end . 100amp wylex isolator to protect swa and armour will be earthed both ends .

 

[brianmoooore]

Wylex DSF60M . . Wylex 60A Domestic Switched Fused Unit - https://www.screwfix.com/p/wylex-60a-domestic-switched-fused-unit/4848J?tc=IC4&ds_kid=92700055281954493&ds_rl=1249401&gclid=Cj0KCQjwsqmEBhDiARIsANV8H3Yp-RMwJlSdgcWFJeIhp8cUjh1zFxiNDkGB6vUoI0RNsfuSEMLGPvMaAixlEALw_wcB&gclsrc=aw.ds

 

[user786786]

Wylex DSF60M . . Wylex 60A Domestic Switched Fused Unit - https://www.screwfix.com/p/wylex-60a-domestic-switched-fused-unit/4848J?tc=IC4&ds_kid=92700055281954493&ds_rl=1249401&gclid=Cj0KCQjwsqmEBhDiARIsANV8H3Yp-RMwJlSdgcWFJeIhp8cUjh1zFxiNDkGB6vUoI0RNsfuSEMLGPvMaAixlEALw_wcB&gclsrc=aw.ds

thanks . can gland straigt into that . quite pricey though

 

[pc1966]

henley will be both end . 100amp wylex isolator to protect swa and armour will be earthed both ends .

An isolator will not provide fault protection! It is simply a switch. The rating (e.g. 100A) is the maximum it can safely handle, and it is assumed there is some other means of limiting the current to that level.

You need to use a fused-switch switch, such at the one @brianmoooore linked to.

 

[littlespark]

Use an underground torpedo joint at the short end to extend the SWA. ?

or move the CU reach the cable. Might have to extend or rewire the outgoing circuits.

Seriously rethink the house end. As stated above, an isolator is not a protective device.

 

[Julie.]

Thanks for reply Everyone


Garage /outbuilding end

Swa is coming out of concrete but too short too gland directly into the Metal CU so
the Swa has been glanded into a metal adaptable box then then outer sheathing removed to show the three single cores . two of them have been run ( for about 10 inches )into seperate henley boxes . third core used as earth to garage cu . swa and henleys all trunked over .

then 25mm tails to the consumer unit length about 450mm each.

the consumer unit in garage is a crabtree starbreaker and has two 6amp rcbos / and two 32 amp rcbos protecting the outgoing circuits .


main House end

The utilty supply comes from the Main Fuse which is sealed but i suspect a 80amp .
This goes off to a 100amp isolator which the utility company fitted .
From here we have 25mm tails to henley blocks , from the henley blocks we then have 25mm tails to the main house consumer unit . ( 7 circuits protected by Rcbos)

The earthing Is TN . 16mm earth wire from utilty supplier to earth block . then 16mm to house CU 10mm to gas 10mm to water .

the SWA run starts here
I wanted to run two 25mm tails from henley to a Wylex 100amp isolator ( couldnt find a lower amp one) connect the Swa which runs to the garage

OK

There are a number of issues, if you have used an isolator, this is merely a switch, and provides no protection to the cable.

This cable must be provided with both overload and fault protection, usually via a fuse switch (assuming swa all the way).

One way of back-checking your work, is to imagine what an experienced person would assess the work both as an initial installation and as an eicr. If you did this it would attract a C2 for both missing fault and for missing overload protection (2×C2).

I still don't quite understand the boxed in part, if this is proper trunking then that's one thing, however if not and it's a matter of being behind metal/plastic/timber covering that looks architectural then there are further issues, firstly as the cable has only a single layer of insulation this would attract a C2 - a second layer must be applied, a colouring sheath would not meet the requirements as it should not be removable without tools/destruction and is generally not of the required thickness/insulation.

In addition, now this cable is hidden less than 50mm in the building structure, rcd protection is required, some would code this as a C2 some C3, I would normally consider it C3, however as a substantial supply to a sub-main I would give this a C2 - driving a nail into a 1mm^2 - 2.5mm^2 cable protected by a 6A/32A mcb is one thing, into a 16mm^2 unprotected cable is another!

If it's a matter of a few ft, can you not move the garage cu? Or install proper steel conduit/trunking

 

[pc1966]

As @Julie. points out, can you enclose any extension in proper earthed metal conduit or trunking?

If extending SWA as @littlespark suggest then you can use these sort of joints that are suitable even for directly buried cables for 16mm 2-core:

S10 10-16mm Straight Resin Joint Kit for Cables up to 16mm 2 Core

Proven underground cable jointing system

www.cef.co.uk

Or for 16mm 3-core:

S16 16-25mm Straight Resin Joint Kit for Cables up to 25mm 2 Core

Proven underground cable jointing system

www.cef.co.uk

But if doing so then please carefully read and follow the joint instructions fully!

 

[timhoward]

As @Julie. points out, can you enclose any extension in proper earthed metal conduit or trunking?

If extending SWA as @littlespark suggest then you can use these sort of joints that are suitable even for directly buried cables for 16mm 2-core:

S10 10-16mm Straight Resin Joint Kit for Cables up to 16mm 2 Core

Proven underground cable jointing system

www.cef.co.uk

Or for 16mm 3-core:

S16 16-25mm Straight Resin Joint Kit for Cables up to 25mm 2 Core

Proven underground cable jointing system

www.cef.co.uk

But if doing so then please carefully read and follow the joint instructions fully!

I think he said he's using 3 core and I'd also agree this is a good way forwards.
Worst one I ever had to do was in a deep muddy puddle when a plumber got excited with a mini digger. Most annoying was it was a cable I'd installed myself 12 months earlier, and even though covered in cable bricks and marker tape he still tore it up so badly a new section was needed....

 

[littlespark]

A mini digger and a plumber: that’s all you need to find the route of a buried cable!


if you’re using the resin type joints..... do it on the flat, so the resin pours and levels properly.... and wear the gloves provided! That stuff sticks to everything!!

 

[MJPD29]

Thanks for reply Everyone


Garage /outbuilding end

Swa is coming out of concrete but too short too gland directly into the Metal CU so
the Swa has been glanded into a metal adaptable box then then outer sheathing removed to show the three single cores . two of them have been run ( for about 10 inches )into seperate henley boxes . third core used as earth to garage cu . swa and henleys all trunked over .

then 25mm tails to the consumer unit length about 450mm each.

the consumer unit in garage is a crabtree starbreaker and has two 6amp rcbos / and two 32 amp rcbos protecting the outgoing circuits .


main House end

The utilty supply comes from the Main Fuse which is sealed but i suspect a 80amp .
This goes off to a 100amp isolator which the utility company fitted .
From here we have 25mm tails to henley blocks , from the henley blocks we then have 25mm tails to the main house consumer unit . ( 7 circuits protected by Rcbos)

The earthing Is TN . 16mm earth wire from utilty supplier to earth block . then 16mm to house CU 10mm to gas 10mm to water .

the SWA run starts here
I wanted to run two 25mm tails from henley to a Wylex 100amp isolator ( couldnt find a lower amp one) connect the Swa which runs to the garage

Have you got a pic? Hard to visualise

 

[user786786]

OK

There are a number of issues, if you have used an isolator, this is merely a switch, and provides no protection to the cable.

This cable must be provided with both overload and fault protection, usually via a fuse switch (assuming swa all the way).

One way of back-checking your work, is to imagine what an experienced person would assess the work both as an initial installation and as an eicr. If you did this it would attract a C2 for both missing fault and for missing overload protection (2×C2).

I still don't quite understand the boxed in part, if this is proper trunking then that's one thing, however if not and it's a matter of being behind metal/plastic/timber covering that looks architectural then there are further issues, firstly as the cable has only a single layer of insulation this would attract a C2 - a second layer must be applied, a colouring sheath would not meet the requirements as it should not be removable without tools/destruction and is generally not of the required thickness/insulation.

In addition, now this cable is hidden less than 50mm in the building structure, rcd protection is required, some would code this as a C2 some C3, I would normally consider it C3, however as a substantial supply to a sub-main I would give this a C2 - driving a nail into a 1mm^2 - 2.5mm^2 cable protected by a 6A/32A mcb is one thing, into a 16mm^2 unprotected cable is another!

If it's a matter of a few ft, can you not move the garage cu? Or install proper steel conduit/trunking

Thanks again everyone have been very helpful and have brought up some issues which i will adapt .

---house end do not use 100amp isolator ,instead replace with a 63 amp wylex fused switch will protect the live feed of the SWA .

--- garage end the wiring is already in situ so i dont fancy digging up or extending CU . so i will use a large adapatable box to put the exposed single cores and henley boxes in . That should be up to regulations ?


--i was understanding that i dont need RCD protection for the SWA as the armor is earthed at both ends. Will that not be sufficient ?

 

[user786786]

here is the garage end

 

[Julie.]

--i was understanding that i dont need RCD protection for the SWA as the armor is earthed at both ends. Will that not be sufficient ?

Correct, but at the extended end it is not SWA all the way to the CU.

If you took the SWA into the CU then it would be OK

 

[user786786]

Correct, but at the extended end it is not SWA all the way to the CU.

If you took the SWA into the CU then it would be OK

Ahh okay so if put in large adapatable box of metal construction next to the consumer unit will that be appropriate.?