Particulars of the installation at origin?

[DiscoDave]

I'm about to start some work on a detached garage. Sockets lights etc etc.

From the supply head there is a 63A switch fuse, that takes a set of 25mm tails to the board which is situated about 4m away.

From the board it goes in 16mm 3c SWA to the garage where it is terminated into a four way Metal clad DB.


so for my testing, is the origin of this install at the consumer unit in the house or the switch fuse?

for the test sheets do I record each sub main on my test results or just the one that supplies that garage?

as I have not installed any of it i'm just doing the garage install this will be recorded but i want to make sure I record the right things, previously i've done the whole shooting match so there's been no confusion.

one last thing, To eliminate the risk of parallel paths on the earth it is correct to only terminate the swa armour to earth at one end. is it acceptable to do this at the garage end?

normally i'd do it at the supply end but at this supply end it is plastic and at my end it is a metal db. assuming the answer is no - has to be connected at the supply end how do i go about it at the other end? plastic washers?

Thanks in advance
dave

 

[Mark.W]

Just my opinion but......

I'd say the origin is at the CU in the house.
I'd only record the garage sun main.
Yes you are correct, only terminate SWA at one end, garage end is fine.


Others might have different views.

 

[DiscoDave]

The swa is not rcd protected, is that what you mean? where as the garage is/will be.

cheers
dave

 

[JUD]

normally i'd do it at the supply end but at this supply end it is plastic and at my end it is a metal db. assuming the answer is no - has to be connected at the supply end how do i go about it at the other end? plastic washers?

If you want to earth it at the supply end, terminate your SWA in a galvanised adaptable box next to the CU and then run a flylead from this to the MET.

 

[DiscoDave]

swa is already terminated at the db end into a plastic box, but yes i could take a flying lead from it. But if i do that as it is then it will create a parallel path down the armouring.

so given that the db on the other end is metal and is already earthed to the armour is the ok or should it be the other way round?

cheers

dave

 

[JUD]

If it was me I would terminate in galvanised box at supply end with flylead to MET and plastic box at garage end to insulate it from metal clad DB.

 

[DiscoDave]

i thought that might be the solution! any one got any other reasons why i could leave it as it is before ripping it to bits?

 

[Addlight]

What am I missing about your concern on parallel paths, Disco?

Yes, you want to disconnect them for testing, but paralleling up with armour after that is going to give you lower Zs, which is good - yes?

Apropro nothing in particluar, I just finished a job with SWA from house to garden and used Piranha with Wiska IP66 box. Piranha's are great, Wiska pretty good, but they don't play nicely together...

Piranha 20mm Earth Locking Nut

 

[Amp David]

I fthe supply end is into aa insulated unit, then just take a fly lead from the banjo.

I always earth at the supply end as it is here that you cpd is located.

 

[DiscoDave]

@adlight, Maybe i've got the wrong end of the stick here, yes as you say parallel paths reduce impedance, so as long as i disconnect it for testing ie giving the worst case scenario a parallel path is acceptable?

I'm using this job for my part p assessment, for the last four years i've been working to designed drawings where someone else is responsible, so just getting back in to the swing of not being to tight to have a 3c instead of a 2c and using swa as earth.

many thanks all!

 

[Amp David]

I have the same setup. 3 core SWA fed from an insulated CU feeding a metal clad garage CU.

Nothing was said about on my assessment which i've not long had.

 

[Addlight]

That's the way I've been doing it - but like you I'm fairly new to this with my NICEIC assessment scheduled at end of month.

So - as you say - I'd record CPC only for R2 in test results - to make sure it meets the required disconnect times. Then connect up the armour as parallel path, which will reduce R2 - and give overall lower Zs for the circuit. In turn that gives better disconnect time.

Anyway - that's what I've been taught!

Sorry to have wandered off the main point of the thread.....