Another random question

[hightower]

Pretty sure you all know by now I like to dream up random scenarios.

So let's say running SWA to an out building, but the consumer unit is a tricky run that would make it difficult to get SWA all the way to it. Would you then run T+E say from the consumer unit, through the external wall to some form of IP rated junction box, and then join the SWA in this external junction box?

 

[Pete999]

Don't see why not

 

[Simonslimline]

Pretty sure you all know by now I like to dream up random scenarios.

So let's say running SWA to an out building, but the consumer unit is a tricky run that would make it difficult to get SWA all the way to it. Would you then run T+E say from the consumer unit, through the external wall to some form of IP rated junction box, and then join the SWA in this external junction box?

Best to always avoid joints in a circuit where possible. What is making it so tricky?

 

[hightower]

Best to always avoid joints in a circuit where possible. What is making it so tricky?

Dunno, it's in my head lol. But for hypothetical reasons what would be the best way to proceed? Surely joining it would be no different than extending circuits to move a CCU?

 

[slingshot2000]

I did something like this recently. I terminated the SWA into wago box and the took the sheathed inner cores through the wall, in plastic conduit, straight into the back of the consumer unit. I took an earth, from the same terminal I put cpc from the SWA in, back through the conduit to terminate onto the SWA gland banjo.

 

[telectrix]

bear in mind that if the T/E from the CU is buried <50mm deep in plaster, it requires RCD protection.

 

[Deleted member 26818]

4 options:
Run the whole circuit from CU to outbuilding in T&E.
Run the whole circuit from CU to outbuilding in SWA.
Run the exterior part of the circuit in SWA, glanding the SWA into an adaptable box and the interior part of the circuit in T&E.
Run the exterior part of the circuit in SWA, glanding the SWA into an adaptable box with the cores long enough to reach the CU.
Fith option is to use a different cable altogether.

 

[hightower]

bear in mind that if the T/E from the CU is buried <50mm deep in plaster, it requires RCD protection.

Does penetrating through a wall at a right angle to go internal to external count for this?

 

[Deleted member 26818]

Cables which pass through walls do not require RCD protection, as the cable entry and exit points are visible.

 

[Flanders]

What He says /\ /\ /\ /\

 

[Dave OCD]

Does penetrating through a wall at a right angle to go internal to external count for this?

Not at a right angle, I always go up hill a bit from outside to in. :icon12:

 

[telectrix]

Does penetrating through a wall at a right angle to go internal to external count for this?

no.because the cable is nit parallel to the surface of the wall. it just goes through it.

 

[Skimpy Wan]

If there is an internal ring final circuit could you not extend a leg in a socket, drill through a wall and place an IP rated socket and then SWA from there to have a couple of sockets there (& down rate a Switched FCU for a lighting circuit)?

 

[telectrix]

If there is an internal ring final circuit could you not extend a leg in a socket, drill through a wall and place an IP rated socket and then SWA from there to have a couple of sockets there (& down rate a Switched FCU for a lighting circuit)?

you'd need to fit a 13A FCU after the house socket as you'd be adding more than 1 socket on a spur. would be bad design IMO.

 

[Skimpy Wan]

If the garage socket & outside socket were incorporated as 1 ring final circuit why couldn't you just add a FCU for the lighting to be down rated?

 

[telectrix]

If the garage socket & outside socket were incorporated as 1 ring final circuit why couldn't you just add a FCU for the lighting to be down rated?

could be donelikethat, butthe problem you would always have is a fault in the garage would trip the RCD on the house RFC, thus entailing a trip back to the CU from the garage whenever you plugin your old faulty drill/leccy fire/welder/kettle/whatever.

 

[Skimpy Wan]

They'll just have to remember to leave the back door unlocked then! Lol

Another question then ...

If the garage is separate to the dwelling how do you supply this and on what type of earthing system (I.E. TN in dwelling and a TT for garage)?

 

[hightower]

could be donelikethat, butthe problem you would always have is a fault in the garage would trip the RCD on the house RFC, thus entailing a trip back to the CU from the garage whenever you plugin your old faulty drill/leccy fire/welder/kettle/whatever.

Which leads on to another question I had. Let's say there's a whole new distro circuit to be ran to a garage. You run a cable to a spare way on your rcd protected board, and then on to the distro board in the garage. Brilliant because you can now split the garage circuits however you like, except any earth fault is still going to trip the rcd at the supply board, meaning a trip to the board in the dark.

I'm guessing the trick is to run it from an s type rcd so there's some discrimination, but the few I've come across haven't been wired like that.

 

[telectrix]

always extend the TN earething to the garage unless eatraneous parts in garage can't have adequate bonding due to size of supply cable from CU ( i.e. where 10mm bonding is required on a PME system)

 

[Skimpy Wan]

Similar thought process!

My concern with a time delay RCD in the house is that all circuits would then be time delayed in the dwelling (hence my query about making the garage a TT system)?

 

[telectrix]

Which leads on to another question I had. Let's say there's a whole new distro circuit to be ran to a garage. You run a cable to a spare way on your rcd protected board, and then on to the distro board in the garage. Brilliant because you can now split the garage circuits however you like, except any earth fault is still going to trip the rcd at the supply board, meaning a trip to the board in the dark.

I'm guessing the trick is to run it from an s type rcd so there's some discrimination, but the few I've come across haven't been wired like that.

as long as the cable from the CU to the garage does not require RCD protection ( e.g. SWA or cables inside house are not buried<50mm deep ) then feed from a non=RCD way in a hi integrity board or split tails before CU ( this would entail fitting a 2 pole isolator befor the split if not already in situ, and a separate OCPD for the garage feed.).

 

[ruston]

Split the tails , armour direct to metal clad switched fuse, direct to shed . No need for RCD at supply end.

 

[hightower]

as long as the cable from the CU to the garage does not require RCD protection ( e.g. SWA or cables inside house are not buried<50mm deep ) then feed from a non=RCD way in a hi integrity board or split tails before CU ( this would entail fitting a 2 pole isolator befor the split if not already in situ).

The installs I've seen (not ones we've done, ones we've come across) all seem to come from a 40a breaker or done such on part of the rcd protected

 

[telectrix]

The installs I've seen (not ones we've done, ones we've come across) all seem to come from a 40a breaker or done such on part of the rcd protected

only problem there is as i said in post #16.

 

[hightower]

only problem there is as i said in post #16.

Yeah hence why it's been chewing me to bits - surely not the best practice

 

[Leesparkykent]

If the house is TT then the distribution circuit may need to be on an RCD due to high EfLI.

 

[Deleted member 26818]

I'm guessing the trick is to run it from an s type rcd so there's some discrimination, but the few I've come across haven't been wired like that.

If the RCD has been installed to provide additional protection for sockets, cables concealed in walls or circuits of a location containing a bath or shower, it will not be an 'S' type.