How To terminate SWA???

[PeteE]

I've just had a new kitchen fitted in the house and while doing some electrical work, the spark basically condemned the existing wiring going out to my detached garage.

It seems the previous owner has used ordinary an extension cable to take the power from the CU in the house, out to a CU in the garage. The good news is that he run it plastic ducting so replacing it will not be too difficult.

I have bought 12m of 6mm 3 core SWA plus two glands, but I have realised I have no idea how to fit the glands! Does anybody know of a online diagram which would explain how it all fits together?

I think I'm going to need to fit two adaptable boxes and have T&E tails back to the respective CU's...I assume the T&E tails will need to be 6mm as well..

At present, the existing ducting comes up in the standard external meter box on my house. Would it be ok to fit an adaptable box in there? I had a chat with the Scottish Power spark who replaced the meter, and he said it was OK....

Finally, can somebody explain the earthing protocols involved?

At the meter box end of things, can I pick up an earth in there or do I have to get an earth back to the house CU?

At each end of the SWA, do the earth core and strap linking the steel armouring both go back to the same earth point or do I only need to worry about terminating the earth core?

At the garage end there is a local earth via an earth spike and earth cable..

Do I need to reconnect this up if I am picking up an earth from the house? BTW, the house is not a PME installation according to the Scottish power spark...

Thanks in advance,

Peter

 

[Spark123]

Does anybody know of a online diagram which would explain how it all fits together?

//www.diynot.com/wiki/electrics:installation_techniques:swa_gland

I think I'm going to need to fit two adaptable boxes and have T&E tails back to the respective CU's...I assume the T&E tails will need to be 6mm as well..

It all depends on what size the supply is and how the cable is installed. Is it on an MCB/cartridge fuse?

At present, the existing ducting comes up in the standard external meter box on my house. Would it be ok to fit an adaptable box in there? I had a chat with the Scottish Power spark who replaced the meter, and he said it was OK....

Not sure - the electric boards don't really like you fixing anything onto their board in case you want E7 or they have to fit something else at a later date.

At the meter box end of things, can I pick up an earth in there or do I have to get an earth back to the house CU?

Pick up the correct CPC for the circuit back at the origin of the circuit i.e. the consumer unit.

At each end of the SWA, do the earth core and strap linking the steel armouring both go back to the same earth point or do I only need to worry about terminating the earth core?

Earth both the outer sheath and as you have the spare core, sleeve the black core as CPC and also use that as a CPC.

At the garage end there is a local earth via an earth spike and earth cable..
Do I need to reconnect this up if I am picking up an earth from the house? BTW, the house is not a PME installation according to the Scottish power spark...

If it isn't TN-CS (PME) then, assuming TN-S, you may use the DNO supplied earth without having to worry about the correct sizing for PME protective bonding.
Do you have anything which needs bonding in the garage i.e. metal water supply etc?

 

[Lectrician]

Is the cable you bought 2 core or 3 core?

Exporting an earth is fine, with PME you need to take extra precautions which is why most people do not bother.

If you have a meter box, it is a little rare (certainly not unheard of) to have a TN-S in the 'typical' sense as most people see it. By this I mean that you certainly will not see a paper insulated lead sheated cable terminated into a meter box. I would suspect you either have a TN-S derived from a spit concentric cable or seperate earth conductor, or simply have a TT supply. (or of course a PME and your eng is incorrect!).

I was going to explain how to terminate SWA, but the more I typed the more I realised it is not that simple to describe in just words!

Maybe one of us can take the time to video it one day!

 

[PeteE]

Thanks for the quick replies gents..

Just to recap, the SWA feeding the garage will be 6mm 3 core and no more than 12 m for the entire run...

In the garage, the CU is a 2 way 40A 30mA RCD unit..it has a 6A and 16A MCBs fitted currently...

With regards the meter box, I've just had white meter/E7 removed along with the separate E7 CU in the house.

The Spark doing the kitchen wiring has terminated the old E7 tails in a spare MCB (32A) on the remaining house CU...The other end of the tails currently terminate in a "junction box" in the meter box..That end was done by the Scottishpower Spark (at my request) with this project in mind.

I would like to take the SWA directly into the junction box, but its not really suitable for this, hence why I think I need to fit an adaptable box...

With regards earthing the SWA in the meter box, if I have to get an earth tail back to the CU from the meter box, its going to be a real pain; its a pity I can't pick up the earth directly in the meter box as I am sure there is one in there I could terminate to..

With regards the existing earth rod, there was an old external GPO telephone bell set fitted on the garage wall and I strongly suspect the earth rod was originally provided as part of that telephone installation but somehow ended up being connected up as the garages electrical earth ...

I know about GPO earths and years ago phones sometimes required a earth rod to work eg the old party lines ect

Regards,

Peter

 

[Lectrician]

God - Party lines and earth rods......thats going back.

A single line would serve two properties (if you lifted the phone and your neighbour was already using it, you could here them).

For the ringing, it was sent down either the A or the B leg depending on the property called, with the earth via the rod being '0v'.

If you where posh you also had a red light by your phone to show if the line was already in use.

Replaced by DACS years and years and YEARS ago!

DACS is currently being replaced by extra line plant where required as it cannot be used with broadband.

DACS provides two completely seperate lines on a single 'line' from the exchange. You cannot tell if you are fed via a DACS unless you use dial up internet, where you will find you have a fixed speed of 33kbs.

Completely off topic....sorry.

 

[PeteE]

Lectrician,

And don't forget that with "Shared Service" if you reversed the polarity of your i/c line, your calls would bill on the other Subs meter!

And if anybody is still using a dial up modem for accessing the Net, a DACS will effectively cap you at around 15K IIRC...

Regards,

Peter

 

[Taylortwocities]

You didn't need to reverse the line, you got dial tone (billed to you) by placing an earth pulse on the A leg. Your neighbour got his dial tone (billed to him) by placing an earth on the B leg.

All you had to do was earth the B leg and make your call to granny in Singapore!

Ahh the 706 telephone with the button on the top.....

Remember Plan 4s? .
I was in a house the other day and they still had the Plan 4 jacks around the house. (Jacks 96A IIRC)

 

[PeteE]

All you had to do was earth the B leg and make your call to granny in Singapore!

Ahh the 706 telephone with the button on the top.....

Your quite right, I'd forgotten that!

I do remember pouring water on the earth spike though!

Remember Plan 4s? .
I was in a house the other day and they still had the Plan 4 jacks around the house. (Jacks 96A IIRC)

Plan 4 with the round plug- in jacks? I hated those with a passion, along with HES's and 41wire!

 

[Taylortwocities]

Still got a pair of 81's around here somewhere. The oil dag dried up last century..

Those were the days, two step selectors. Call tracing by running around the exchange.. Lovely girls on the manual switchboard too - I used to have to crawl around under their legs when changing the jack cords - that was my excuse anyways

 

[TicklyT]

...... Not allowed into the switchroom unless your dustcoat was buttoned up - They didn't want the girls getting excited...

.....lift up the weights in the back of the board, so the cords suddenly jumped out over the keyshelf.....

I didn't mind fitting HESs - Key an lamp units were worse, especially when someone forgot to cut the straps out the back of the box 1As, and melted the cables.

Relay bashing

Wiper changing

Bank cleaning

Nostalgia isn't what it used to be!

 

[Taylortwocities]

Happy days. I worked in a repeater station for a while. I spent all the time making a guitar amplifier. (Except when the AE was visting).

 

[Chri5]

Still got a pair of 81's around here somewhere. The oil dag dried up last century..

Those were the days, two step selectors. Call tracing by running around the exchange.. Lovely girls on the manual switchboard too - I used to have to crawl around under their legs when changing the jack cords - that was my excuse anyways

I worked at BT from 79 to 85 doing PABX 7 installations- fit 8 x recall switches to 700 series phones and that was 8 x 10p work codes- a days work!

81's were really AT1's but made to a number, as were all small tools, I've still got a tool wallet No3 with screw drivers 1-6 and a few A's.

Lacing, gun wrapping, tag soldering, custom made wire looms on wallboard for dealer systems and special K&L units.
Loved it when I was 1st shown K&L units with the relays pushed- disco time

When krone came out and K&L's came with viking plugs 226, life became very easy.

As for HES systems, it wasn't the wiring it was the ecking straps that needed adding, moving and removing in the base that were the mare.

 

[Chri5]

Here's a picture by picture step to terminating SWA via standard glands.

http://www.ultimatehandyman.co.uk/armoured1.htm

For text and fuller detail see linky

 

[Spark123]

That is rough! And don't fit the banjo between the gland and a plastic enclsure too.
Either double locknut inside with the banjo between the two locknuts or use a piranha.

 

[RF Lighting]

Using shears to cut SWA aint gonna do them much good.

Snipping the armour to all different lengths with side cutters? Hmmm.

I'd like to see them try this method on something a bit bigger then 2.5mm² 3 core