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