Distribution Circuit Q ..

[Danny]

Chaps .. does a distribution circuit need to be RCD protected ?

Installing sockets, lights etc to garage/workshop ... thinking along the convenience line of things .. Existing hi-integrity unit with spare ways by the main switch ... Dist circuit to go from an MCB here to the new workshop CU which will be main switch, rcbo for lights, rcbo for sockets and mcb for further dist circuit to shed a little further on where same again, new CU with rcbo for lights and rcbo for sockets ... so, you see where i'm going here .. convenience in the form of if the sockets go lights and further building doesnt go as well, etc ..

 

[green-hornet]

There is no requirement to rcd a supply cable providing that the cable is mechanically protected and is suitable for the installation with regards to external influences.

So you could use armoured cable with earthed sheath and internal earth core if required for TT installations or extra protection.

It can be a pain in the preverbial but I like to run my cables in conduit if possible so you get extra protection underground.

 

[ianmacd]

If you do RCD protect, don't forget to take into account discrimination with the RCBO's too.

Ian.

 

[Danny]

That's what I thought ... SWA is the plan of attack using the 3rd core for earth ... and hoping to avoid tripping conflict by not doubling up with RCBOs .. lovely old job ..

 

[a1]

If you're using SWA - don't forget to Earth the Steel Wire at the house end.

Then Terminate into PVC the Shed end. NOT taking the earth Steel Wire into the Shed / Garage CU.

NIC are keen on that too. (Don't know about the others, but I should imagine they are too).

 

[ianmacd]

Why, if he is already exporting the earth?

 

[a1]

It is something the "High Almighty NIC" insist on.

Just incase some muscular chap put a shovel through it or something. Argue that the third conductor is an earth and they will say that it meakes not a jot of difference.

 

[ianmacd]

Another reason not to be NIC me thinks. Their random rule making is laughable at times.

 

[Danny]

This whole exporting earth thing confuses the hell out of me ... if the garage/shed system is properly earthed with continuity back to the MET and acceptable test results obtained why break and stake it ?

 

[ianmacd]

There are a few threads on here about it. Depends on the earthing arrangements really. Have a search though.

 

[a1]

Another reason not to be NIC me thinks. Their random rule making is laughable at times.

I agree.

I just hope that the other Part P Providers make the public, Councils and Insurance companies more aware of their presence.

The NIC are at the top of most people's lists at the moment. :|

 

[NozSpark]

It is something the "High Almighty NIC" insist on.Just incase some muscular chap put a shovel through it or something. Argue that the third conductor is an earth and they will say that it meakes not a jot of difference.

The reason behind dropping the earth at the Sub DB (full TT installation) is because of circulating earth currents,,, and has nothing to do with anything else

Personally I think that having an earth conductor in addition to the armour sheath makes a lot of sense.. I have far too many rotten SWA sub mains......... It only takes a small cut in the PVC sheath and the armour will be done for..

 

[Andy™]

It is something the "High Almighty NIC" insist on.Just incase some muscular chap put a shovel through it or something. Argue that the third conductor is an earth and they will say that it meakes not a jot of difference.

they can insist, but since its well within 7671 to export an earth, they cannot stop you from doing it.

 

[a1]

they can insist, but since its well within 7671 to export an earth, they cannot stop you from doing it.

I am not saying you can't export an earth - I was stating the NICs take on earthing the armour from the House CU to The shed and not carrying it on to the Garage / Shed CU and using it.

Armour is earthed from House CU to Shed CU and terminated there. Just to protect the swa.

 

[Andy™]

I am not saying you can't export an earth - I was stating the NICs take on earthing the armour from the House CU to The shed and not carrying it on to the Garage / Shed CU and using it.Armour is earthed from House CU to Shed CU and terminated there. Just to protect the swa.

but there view is different from 7671. they cannot enforce it or mark you down for it

 

[NozSpark]

I am not saying you can't export an earth - I was stating the NICs take on earthing the armour from the House CU to The shed and not carrying it on to the Garage / Shed CU and using it.Armour is earthed from House CU to Shed CU and terminated there. Just to protect the swa.

Where did you get that idea from??

Is it first hand information or more grape vine stuff??

I've never come across this from the NIC themselves,, just some contractors thinking they are the dogs and misinterpreting the regs..

One local guy thinks you cannot use a RCD as a main switch and therefore puts an isolator in front of it and then the MCB's..

You also get the single point of isolation thing,, you do not have to have a single main switch in a domestic install. (Check out the ESC FAQ link in the links page)

 

[a1]

Yes - I know that mate.