TT Submain Design

[Hefferl]

I need to install to a remote building approx 3m away.

The supply at the main building is TT

The main building is NOT a dwelling.

Is this a sensible design?

Henley Block --> PVC Tails --> Insulated enclosure with 100mA S type RCD --> PVC Tails --> Metal switch fuse --> SWA --> Remote Metal CU & 30mA RCBOs

And bearing in mind short distance, would you go with

2 Core SWA and extra earth rod at new building 

3 core SWA no extra rod

3 core SWA and extra rod

Thanks

 

[Jono Pashley]

Split the tails before the RCD, install one S type for the main supply and one for the outbuilding. Id probably go 3 core SWA and drop a extra rod as long as the separation distances are fine

 

[Murdoch]

The more rods the better in TT ................. so 3 core SWA and an extra rod(s) for me

 

[Sidney]

As this is not a dwelling do the boards need to be metal?

And as per Murdoch, the more rods the merrier!!!

 

[Hefferl]

As this is not a dwelling do the boards need to be metal?

And as per Murdoch, the more rods the merrier!!!

No boards do not need to be metal which is why I intend to use insulated for the upfront RCD. 

Metal for the switch fuse as I prefer this to terminate SWA into.

Metal for CU as I like to use SBS boards and RCBOs

 

[UNG]

As this is not a dwelling do the boards need to be metal?

When I last checked the regs there is no absolute requirement for domestic boards to be metal

The more rods the better in TT ................. so 3 core SWA and an extra rod(s) for me

And as per Murdoch, the more rods the merrier!!!

There is no problem with multiple rods as long as they are properly distanced to gain the maximum benefit, quite often see co-located rods that are haphazardly nailed into the ground through clear ignorance that means they are not providing the optimum benefit for the cost

 

[Phoenix]

Consider using double pole RCBOs (or at least SPSN) - The new wylex low profile ones afaik are, but the hager ones, however I belive are *not* Otherwise if you get a neutral earth fault, then yes, it'll take the final circuit rcbo out, but a few hundred milliseconds later you'll loose the time delay trip as the fault is still in place!

 

[Hefferl]

Consider using double pole RCBOs (or at least SPSN) - The new wylex low profile ones afaik are, but the hager ones, however I belive are *not* Otherwise if you get a neutral earth fault, then yes, it'll take the final circuit rcbo out, but a few hundred milliseconds later you'll loose the time delay trip as the fault is still in place!

Yep SBS Trade Sales RCBOs are double pole.