SWA size recommendation

[Escos]

Hello

Could someone please recommend the size of SWA i would need to supply a cu in my garage.? It is ingle phase.

The run of cable will be approximately 23metres. The cable needs to handle a compressor connected via a 32amp plug, a mig welder connected via 32amp and various power tools. Not all the same time though.

I understand that the tails from the meter will have to be split using Henley Blocks and an switchfuse installed. Can anyone advise on how much power suppliers charge for pulling the main fuse and installing a switchfuse please.?

I was thinking of 16mmsquare 3 core, with an earth rod and enclosure at the garage end of the swa. Is this correct procedure regarding the earth, with the cable run being over 20meters. I have read on this forum that it is not recommended to export the earth over long distances.

Any advice would be greatly appreciated.

Thanks in advance.

 

[ban-all-sheds]

Could someone please recommend the size of SWA i would need to supply a cu in my garage.? It is ingle phase.

http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

Make sure you select PVC cable, even if you'll be using XLPE, and 2-core even if you'll be using 3-core.

The run of cable will be approximately 23metres. The cable needs to handle a compressor connected via a 32amp plug, a mig welder connected via 32amp and various power tools. Not all the same time though.

Only you know what the design load will be.

I understand that the tails from the meter will have to be split using Henley Blocks and an switchfuse installed. Can anyone advise on how much power suppliers charge for pulling the main fuse and installing a switchfuse please.?

Ask yours - it varies - some refuse to do it at all.

I was thinking of 16mmsquare 3 core, with an earth rod and enclosure at the garage end of the swa. Is this correct procedure regarding the earth,

That depends, but probably not.

Why 3-core if you aren't going to export the earth?

And what do you propose to do with the armour at the garage end?

with the cable run being over 20meters. I have read on this forum that it is not recommended to export the earth over long distances.

Really?

Any advice would be greatly appreciated.

This is notifiable work, and non-trivial. There is a lot to know to be able to do it safely, and I get the impression you don't know it all.

My advice is to get an electrician for a job like this.

 

[ericmark]

BAS has answered most of the questions. You could read Wiring Matters Issue 16 Autumn 2005 Electrical installations outdoors: a supply to a detached outbuilding which will give you some more information.

The question on exported TN or TT system of earthing is complex and not a simple as just the distance from house.

This will require Part P and either a registered electrician or the LABC and pay their fee. If the latter is path you are taking you will need to find out what they will permit as Electricians we can argue with LABC and explain why we think a path should be taken but as a DIY'ed you will have to do as your told which will likely cost to fit isolator before the Henley Block which likely they will insist is fitted by supplier as you can't draw fuse.

I would guess you will pay more than £200 in fees to take LABC route you may find registered electrician cheaper.

 

[Steve]

For all except a rewire, Doncaster Council charge £100 for Part P notifications.

To the OP, I suggest you use only ONE 32 amp socket, in order that only one of your power hungry appliances can be in use at once. Although on checking TLC's VD calculator, 16mm would be good up to at least 80 amps over that distance. (Is that right???) If this is the case, have both your sockets, and use a 63 amp breaker at the house.

As for exporting an earth, a TNCS should not be exported where there are extraeneous conductive parts, which would need bonding such as water or gas mains.

Do you know what sort of earth you have?

 

[ban-all-sheds]

Although on checking TLC's VD calculator, 16mm would be good up to at least 80 amps over that distance. (Is that right???)

No - 69A.

As for exporting an earth, a TNCS should not be exported where there are extraeneous conductive parts, which would need bonding such as water or gas mains.

If he's using 16mm² he can bond any ECPs back to the MET with that.

 

[JonoPashley]

PME is a piece of trash, bang a rod in and get on with it.

 

[Steve]

PME is a piece of trash, bang a rod in and get on with it.

WTF?

How do you know its a good earth?

You dont mention testing.

 

[ricicle]

PME is a piece of trash....

Which other system lets you know when the suppliers earth is broken ?

 

[JonoPashley]

If you can get anywhere near a half decent earth off a rod any out building is much better served as a TT than being on PME where over distance you will end up with a earth which is above actual ground potential. You also have no reliance on a earth from what is effectively a cost cutting exercise from the DNO's

 

[RF Lighting]

TT is an absoloute last resort IMO.

Can you cite an example of a PME supply earth actually rising to a dangerous voltage above true earth?

 

[JonoPashley]

It rises to nuisance voltages frequently depending how far it is back to the nearest PME point, and in the event the neutral does become severed your return path suddenly becomes your services which are now at mains potential with any RCDs effectively bypassed. Its nothing more than a cost cutting exercise that puts safety last.

 

[Escos]

Thanks for all the advice.

To Ban all Sheds; I never said i "new it all". I proposed to terminate the swa into a galvanised adaptable box.

Thanks Steve for the info,
i think the earth is the TNS system. Earth bonding on the armour of the distributors service cable, earth bonding on the gas and water pipes.

I will be getting an electrician to do the work, iwas just thinking of laying the cable myself and getting it inside both buildings.

Thanks.

 

[RF Lighting]

If it is TN-S then exporting the earth is definatly the best soloution.

Check with your electrician before you lay the cable that he is happy for you to do so, and also he will be able to advise you which rotes a suitable, and how deep the cable needs to be buried.

I would be happy for my customer to lay the cable providing I was happy with the route etc.

Also, your electrician will probably be able to buy the cable cheaper than you can.

 

[Escos]

Thanks RF

I have worked with a friend who is a sparky, unfortunately he has now emigrated. He did a lot of factory electrics working with armoured. I have also laid armoured underground with him as well.

Would it be ok to export the earth using the armour.? Or would it be better to get three core and use the third core as earth.? I know the armour has to be earthed anyway, ive read somewhere that it is better to use a dedicated earth core when exporting earth.?

The cable will take the route under ground floor joists then exiting the building and underground before entering the garage.

I know its difficult to say from your point of view, but what would you charge for a job like this.? A rough estimate would do, if thats possible.

I have priced armoured up today at Newey and Eyre. Got a price for 16m SWA XLPE £87 and also for 25mm SWA XLPE £120.

Thanks RFL

 

[ban-all-sheds]

on PME where over distance you will end up with a earth which is above actual ground potential.

Unlike TN-S, of course.

You also have no reliance on a earth from what is effectively a cost cutting exercise from the DNO's

Unlike TN-S, of course, where your earth path is the incredibly robust and no-expense-spared maintained cable sheath.