New sub board for shed swa advice.

[Jcamerz]

Hi guys new to the forum after bit of advice. My family are installing a new shed in the garden and require a lot of power ie few sockets, lights. I am planning of running a swa fed from 32a mcb from the main board to a sub board.
Have a question-
Shall I install the new 32a mcb in the main board on the RCD side or main switch side?
Thanks

 

[Dillb]

What does it tell your copy of BS7671 about the installation method of the cable needing RCD protection?

 

[LankyWill]

I agree with above but as a general rule it is better to use a cable which omits RCD protection on the distribution side. Just think if something trips in the shed it’s going to take all of the other RCD protected circuits out along with it. Install RCD protection in the shed to cover final circuits.

 

[Michael Sands]

Could you fit an RCBO on non rcd side

 

[johnduffell]

are you planning to earth the swa armor and if so what is the design earth loop impedence via the armor at the far end? also what Type is the MCB you are planning to use?

 

[Pete999]

are you planning to earth the swa armor and if so what is the design earth loop impedence via the armor at the far end? also what Type is the MCB you are planning to use?

 

[Pete999]

are you planning to earth the swa armor and if so what is the design earth loop impedence via the armor at the far end? also what Type is the MCB you are planning to use?

You should always earth the Armour

 

[Octopus]

What’s the earthing arrangement ?

Part p ?........

 

[johnduffell]

You should always earth the Armour

I was not suggesting that they shouldn't, but I'm sure there's a lot of SWA with no earth on the armour.
You wouldn't get any of the benefits of SWA but you'd still get the cost, so it'd be pointless to install RCD protected SWA where normal multi core cable would be allowed.

 

[Deleted member 9648]

What’s the earthing arrangement ?

Part p ?........

Never heard of a Part p earthing arrangement...….

 

[Jcamerz]

Thanks for the replies guys, I was planning on using swa because because it's going to be run external but clip direct not buried at any point.
I did think RCD only at the sub board would be the best setup.
Earthing arrangement is TN-CS
Now the issue with earthing the armour is the main board is plastic so the 'o ring' would be useless but it will be done on the new sub board. Earthing will be identified using the black core both ends.

 

[Dillb]

You can still earth the armourings when terminatimg a SWA into a plastic enclosure, but being a electrician you would of known that anyway wouldnt you?

 

[telectrix]

clue might be "earthing nut"

 

[LankyWill]

Use a Pyranah nut for plastic enclosures

 

[Strima]

 

[johnduffell]

earthing the armour at the downstream end is OK but it would slow down the disconnection time for faults near the origin. and hopefully no extraneous conductive parts in the outbuilding?

 

[Gavin John Hyde]

I might be wrong but im assuming the op is not an electrician as some of his replies are lacking even basic knowledge.
I am surprised the thread is open still as i can see it turning into us designing the whole job.
No mention of how he is getting this signed of by an electrician of bc to comply with part p either

 

[Jcamerz]

Im still in training at the moment this is all new to me, my family will be getting in a local spark but im intrigued to learn the installation method. Thanks for the comments

 

[sparksburnout]

Im still in training at the moment this is all new to me, my family will be getting in a local spark but im intrigued to learn the installation method. Thanks for the comments

"I am planning of running a swa fed from 32a mcb from the main board to a sub board." ????

 

[telectrix]

View attachment 43319

that's no use there's no hole for the gland.

 

[Gavin John Hyde]

"I am planning of running a swa fed from 32a mcb from the main board to a sub board." ????

@sparksburnout makes the case for the prosecution

 

[johnduffell]

earthing the armour at the downstream end is OK but it would slow down the disconnection time for faults near the origin. and hopefully no extraneous conductive parts in the outbuilding?

@netblindpaul since you pressed Disagree, I'm looking forward to your explanation or edit did you mean you have to earth from the head end?

 

[netblindpaul]

@netblindpaul since you pressed Disagree, I'm looking forward to your explanation or edit did you mean you have to earth from the head end?

Yes, you must connect the SWA to the installation earthing system at the supply end.
You should see that when you do your design FMEA.

 

[Octopus]

Yes, you must connect the SWA to the installation earthing system at the supply end.
You should see that when you do your design FMEA.

Reg number please

 

[johnduffell]

Yes, you must connect the SWA to the installation earthing system at the supply end.
You should see that when you do your design FMEA.

I'm not an electrician but do you mean the physical connection must be at the supply end, or just that the armour has to be connected to the earthing system that protects it?
I guess you're suggesting if the cable is cleanly cut quickly enough (5s disconnection time) it may leave an unprotected live conductor physically separated from the cpc that protects it, and possibly shorted to the now floating armour.

 

[netblindpaul]

Reg number please

Regulations 3, 4, 7, 8, & 9

 

[netblindpaul]

I'm not an electrician but do you mean the physical connection must be at the supply end, or just that the armour has to be connected to the earthing system that protects it?
I guess you're suggesting if the cable is cleanly cut quickly enough (5s disconnection time) it may leave an unprotected live conductor physically separated from the cpc that protects it, and possibly shorted to the now floating armour.

One potential failure mode yes.

 

[Octopus]

Regulations 3, 4, 7, 8, & 9

That I simply do not believe .....

 

[Dave OCD]

There are occasions when earthing the armour [when a seperate cpc exists in the cable] can only be carried out at the 'load' end and I can't see any reason why this is detrimental to safety when done correctly. I wish people would stop posting misleading nonsense.

 

[sparksburnout]

There are occasions when earthing the armour [when a seperate cpc exists in the cable] can only be carried out at the 'load' end and I can't see any reason why this is detrimental to safety when done correctly. I wish people would stop posting misleading nonsense.

What are these occasions then?

 

[netblindpaul]

That I simply do not believe .....

Look them up then.

 

[Octopus]

Look them up then.

Can’t this week as my regs book is at home BUT the numbers you quote are not actual regs, they are sections

So best you be a little more constructive with you input ......

 

[netblindpaul]

Can’t this week as my regs book is at home BUT the numbers you quote are not actual regs, they are sections

So best you be a little more constructive with you input ......

No Murdoch they are real Regulations, not clauses.
If you have access to the internet, which you obviously do, then you can look this up.

 

[Octopus]

No Murdoch they are real Regulations, not clauses.
If you have access to the internet, which you obviously do, then you can look this up.

What absolute carp.

Proper regs numbers to back up your somewhat dubious claims please

Or do we need a new rating “fake reg”

 

[netblindpaul]

What absolute carp.

Proper regs numbers to back up your somewhat dubious claims please

Or do we need a new rating “fake reg”

Murdoch they are proper regulation numbers, you are now just showing your ignorance.
BS 7671 is not the be all and end all.
These are the Regulations that you will be prosecuted under.
BS 7671 is your Regulation 29 defence if followed.

 

[Octopus]

Murdoch they are proper regulation numbers, you are now just showing your ignorance.
BS 7671 is not the be all and end all.
These are the Regulations that you will be prosecuted under.
BS 7671 is your Regulation 29 defence if followed.

Regulations in what publication ..... Jackanory?

 

[netblindpaul]

Regulations in what publication ..... Jackanory?

Try the LAW.

 

[Octopus]

Try the LAW.

Hum ...

I think you need to calm down and go back and answer the original point again.

There is no law stating that swa must be earthed at the supply end ...

The question was what is the BS 7671 reg number that you believe refers this to

 

[ferg]

Gawd this is like watching an impending train wreck.

 

[netblindpaul]

Hum ...

I think you need to calm down and go back and answer the original point again.

There is no law stating that swa must be earthed at the supply end ...

The question was what is the BS 7671 reg number that you believe refers this to

No your question was, what REGULATION, you actually said in post #23 "Reg number please"
Which I then gave you and since then you have been disagreeing with me.
You said NOTHING about BS 7671, you asked for a Regulation, not a clause in a standard.
Remember, Regulations are law, BS 7671 is a standard.
The numbers I quoted are the law that you would be in breach of.
Try THE, Electricity At Work Regulations 1989 (As Amended).
Also if you want clauses from some industry guidance try...
522.6.201, .202, .203, .204
522.8.10
543.3
IET GN8 guides you to EAWR on this topic just for your guidance.

 

[netblindpaul]

Oh and just for your delectation 134.1.1

 

[netblindpaul]

Also 510.3

 

[sparksburnout]

Is it not just common sense that it should be earthed at the supply end? What if it got severed completely and then re-energised, the armour would not be earthed. Mind you round here there is loads of it not earthed at all, seems to be a bit of a blind spot with a lot of contractors.

 

[johnduffell]

Gawd this is like watching an impending train wreck.

A disagreement is merely an opportunity to learn something new! I certainly did, not sure about anyone else..

 

[Deleted member 26818]

The EAWR does not apply to a domestic installation.
SWA should be earthed, otherwise it won’t work as designed.
It should a earthed or connected to the same earthing system as used by the protective device protecting the SWA.
Connecting the armour to one of the cores at the load end of the cable would require the Zs measurement would have to be taken at the supply end of the armour.
Not sure whether the Zs would then be low enough for the protective device to operate?

 

[telectrix]

i think EAWR does apply to domestic installations, inasmuch as during any works carried out on the installation, and also the fact that you could consider housewives ( and house husbands for the PC loonies) to be working, even if only using a dishwasher. tin hat secured with cable ties and a bit of sticky tape.

 

[telectrix]

duplicate

 

[Deleted member 26818]

Sorry but no.
The EAWR applies to employees and self employed persons while they are carrying out work tasks.
The only time a domestic installation would fall within the remit of the EAWR is if there were servants or domestic staff working there.
The EAWR would not apply to the installation, but would apply to the work practices of a tradesperson working in a domestic installation.

 

[telectrix]

i agree. with that. myhousewife analogy may be a bit misleading, but it applies not only to the electrician working there on the installation, but to the safety of other trades e.g. tilers, woodbutchers, gas fitters, etc. ( sod plumbers, they don't deserve consideration. .).

 

[Deleted member 9648]

We work to bs7671 in normal installations. As long as the disconnection time is met there is only a requirment to earth a conductive part that is part of a cable, no set in stone requirement of where. Nobody is ever going to be prosecuted for earthing at the load end and meeting ADS requirements,and to suggest so is ridiculous.
For small SWA cables (1.5/2.5/4.0 etc) with a cpc on shortish runs I'll frequently banjo one end only, whichever end is most convenient. I can see no point in making additional work doing both ends. Longer runs and larger distribution circuits with higher fault currents I'll do both ends.
NICEIC AC and our inspector has never queried it.