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?