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

 

[Julie.]

How are the two single cores installed?

Surface, or within trunking/conduit, what do you mean by boxed in?

What size, and what type of protection - mcb or rcd?

If I understand correctly, the utility supply comes directly into the house cu, then you have henleys spliced into this supply ahead of the cu, two 25mm tails to an unfused switch, then the 16mm swa, to two single cores to the intake main switch of the garage cu.

Is my understanding correct?

I would like to fully understand the arrangement before I comment, because however I visualise the installation I do see a number of issues, but need to be clear as it's no use commenting if I have misunderstood the arrangement.

 

[Darkwood]

You say the SWA is too short but your post is a tad ambiguous, can you clarify it is too short at the garage end and not the supply end as both ends would have a consumer unit at them in most cases.

-How is the SWA protected for short circuit and overload?
-What are the earthing arrangements for the garage, does it need earth isolation and converting to TT or have you correctly wired equipotential bonding if required?
-Why tail up with 25mm, 16mm would have been ideal and easier to write up on the certificate although it's not a problem in 25mm.
-Is this for a customer or your own property just out of interest.
-You have put down on your profile that you are a trainee, who is overseeing this work IE - why are you asking a forum, the work you are doing should be undertaken under instruction and review of a competent person.

PS - a photo saves many a question so if possible can you upload one.

 

[Dustydazzler]

if it’s short at both ends the. I would pull in a new lengthy of swa as I hate multiple jointed sections of cable , looks bear rough

 

[buzzlightyear]

Must have measured with a piece of string. It's better to go over board with SWA then under board. Where mistakes happen.

 

[timhoward]

+1 for some photos and slightly more info about which end is short

 

[MJPD29]

If swa is 16mm no need for tails to be 25mm. When you say single insulated cores will be covered, if they are outside an enclosure then this is absolutely not acceptable and boxing around it all means nothing they MUST he inside an enclosure. What earthing arrangement is this?

 

[timhoward]

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

 

[Dustydazzler]

Its a shame they don't make SWA with double insulated cores as an option

 

[brianmoooore]

Its a shame they don't make SWA with double insulated cores as an option

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

 

[Dustydazzler]

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

Over the years I have seen a few industrial sparks over sheath swa cores with old grey tail sheath that are outside of the enclosure / distribution board.

 

[user786786]

How are the two single cores installed?

Surface, or within trunking/conduit, what do you mean by boxed in?

What size, and what type of protection - mcb or rcd?

If I understand correctly, the utility supply comes directly into the house cu, then you have henleys spliced into this supply ahead of the cu, two 25mm tails to an unfused switch, then the 16mm swa, to two single cores to the intake main switch of the garage cu.

Is my understanding correct?

I would like to fully understand the arrangement before I comment, because however I visualise the installation I do see a number of issues, but need to be clear as it's no use commenting if I have misunderstood the arrangement.

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

 

[user786786]

You say the SWA is too short but your post is a tad ambiguous, can you clarify it is too short at the garage end and not the supply end as both ends would have a consumer unit at them in most cases.

-How is the SWA protected for short circuit and overload?
-What are the earthing arrangements for the garage, does it need earth isolation and converting to TT or have you correctly wired equipotential bonding if required?
-Why tail up with 25mm, 16mm would have been ideal and easier to write up on the certificate although it's not a problem in 25mm.
-Is this for a customer or your own property just out of interest.
-You have put down on your profile that you are a trainee, who is overseeing this work IE - why are you asking a forum, the work you are doing should be undertaken under instruction and review of a competent person.

PS - a photo saves many a question so if possible can you upload one.

it is short only at the garage end . there is plent of slack at the main house end

earthing TN from the utilty end . 16mm to earth block and connect the 3rd core of swa into this and then to the consumer unit in garage .
Overload i was going to use a 100amp wylex isolator ?couldnt find a 63 amp one .

I have used 25mm as i need the practice lol . they are more difficult to work with though =/

its my own property . the original work of running the swa and first fix of my wiring was all been done by my electrican about 18 months ago . i helped him do all the manual work like digging the 600mm trench ! and crawling around the loft spaces .
then with covid last year everything got delayed and delayed further .

 

[user786786]

if it’s short at both ends the. I would pull in a new lengthy of swa as I hate multiple jointed sections of cable , looks bear rough

would have been best option but unfortunately its buried under 600mm of soil in garden and in concrete at the garage end =/

 

[user786786]

Must have measured with a piece of string. It's better to go over board with SWA then under board. Where mistakes happen.

there is a drum roll in the basement where it starts but the other end is too short by 400mm =/. but its buried in concrete . and the consumer unit wiring is in plaster and dont fancy extending that

 

[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.?

 

[timhoward]

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

Sounds ok to me.
If I was having to sort that out I'd probably go for slightly larger box than that one, longer double insulated tails (supported), appropriate grommet, and solder/crimp, tape and heat shrink the joints inside the box, and dispense with the Henleys.
But just throwing a metal box or trunking around it would achieve the same.

 

[Julie.]

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

Yes, as long as the cable run has mechanical protection all the way from the one end from the fuse switch through to the CU that would be OK.

Ideally metallic, but plastic can be OK if not concealed

 

[brianmoooore]

Maybe not quite how I ould have done it myself, but the only thing I can see that is non compliant is the lack of a double sheath on the exposed SWA conductors.
If you have any left over 16mm2 or 25mm2 tails, suitable lengths of the outer sheath slid off and slipped over the exposed brown and grey ends of the SWA will do the job.

 

[westward10]

You can't possibly leave it like that aside from looking awful those conductors are not enclosed. No amount of sleeving will make any difference as you will never be able to completely cover them it will always be exposed where they exit the cable. Crimp some 16.0 6181Y within the adaptable box then bring out through a gland.

 

[user786786]

Sounds ok to me.
If I was having to sort that out I'd probably go for slightly larger box than that one, longer double insulated tails (supported), appropriate grommet, and solder/crimp, tape and heat shrink the joints inside the box, and dispense with the Henleys.
But just throwing a metal box or trunking around it would achieve the same.

Great thanks

 

[brianmoooore]

Why will the ends be exposed anymore than the ends of tails when they connect to service blocks at the DNO service end?

 

[westward10]

Why will the ends be exposed anymore than the ends of tails when they connect to service blocks at the DNO service end?

At the cable end which is poking out of the box. To sleeve them the sleeve would have to enter into the cable or it just sits on top.

 

[brianmoooore]

Sleeve should be pushed on all the way back to the SWA gland in the bottom of the adaptable box. I've done this myself to terminate SWA sub mains into flimsy plastic CUs that wouldn't take a SWA gland direct.

 

[buzzlightyear]

The op wins a crackjack pencil for trying.

 

[user786786]

You can't possibly leave it like that aside from looking awful those conductors are not enclosed. No amount of sleeving will make any difference as you will never be able to completely cover them it will always be exposed where they exit the cable. Crimp some 16.0 6181Y within the adaptable box then bring out through a gland.

going to use a large adaptable box . and large trunking . the asethetics are not that important on this occasion as its a garage . i just want to make sure everything is safely carried out to regs .

thanks