Garage Supply again.

[optician]

Viewed a job today, to reconnect a garage supply and would appreciate your thoughts.

Main board in a shop and garage is for storage ( low use) for a different occupier, so can't
have any faults in garage tripping out shop.

Swa already exists and is 22m in length and 4mm 3 core. It runs half its length along the side of the building and then down through concrete to the garage.

The main board is TT, and the swa will be rcd protected from here on a 32A breaker.

The garage will have a 40 amp rcd protected builders supply unit, an earth rod, bonding to a water supply and two circuits 6amp lights and 16 amp radial.

As the swa is a bit small and bearing in mind voltage drop, I think I'm ok to run the circuits I've specified in the garage?
Or am I forgetting something?

 

[pushrod]

Viewed a job today, to reconnect a garage supply and would appreciate your thoughts.

Main board in a shop and garage is for storage ( low use) for a different occupier, so can't
have any faults in garage tripping out shop.

Swa already exists and is 22m in length and 4mm 3 core. It runs half its length along the side of the building and then down through concrete to the garage.

The main board is TT, and the swa will be rcd protected from here on a 32A breaker.

The garage will have a 40 amp rcd protected builders supply unit, an earth rod, bonding to a water supply and two circuits 6amp lights and 16 amp radial.

As the swa is a bit small and bearing in mind voltage drop, I think I'm ok to run the circuits I've specified in the garage?
Or am I forgetting something?

can't have two ordinary rcds in series (no discrimination) and the 4mm SWA is more than adequate for what you are planning, though might be tempted to protect the SWA with a 20A mcb as It for 4mm 3 core SWA ref method D is only 30amps

 

[optician]

Thanks Pushrod.
I was going to connect the garage earthing system to an earth rod at the garage, but thought not having the two earthing systems connected meant that the rcd's would have discrimination?
Also, I know the Swa is 3 core, but still only single phase and thought the reference method D would be a 37amp rating? (third core being used as earth)

 

[chloebear]

I might be missing something here, but if the supply is for two seperate users then why not separate the supply with a henley service block and have one feed going to the shop and one feed going to the garrage - no RCD discrimination problems then. You will (most likley) encounter nusance tripping with having 2x rcds on the same supply unless one is 'S' type.

 

[top gun]

how do u conect a swa cable into a jointing block

 

[pushrod]

Thanks Pushrod.
I was going to connect the garage earthing system to an earth rod at the garage, but thought not having the two earthing systems connected meant that the rcd's would have discrimination?
Also, I know the Swa is 3 core, but still only single phase and thought the reference method D would be a 37amp rating? (third core being used as earth)

Yes you are right , sorry was in a bit of a hurry when replying and didn't look properly

The SWA does not actually need rcd protection, if you can reposition the breaker on the first CU to a non rcd protected position that would solve that problem.

 

[chloebear]

You connect it in an addaptable box before the henley

 

[optician]

Thanks for the info.
Got some more info and hopefully you could give me some more advice?

Current board in shop 3 way rewireable (only small shop) TT, NO RCD!
Have recommended to owner that the board is upgraded to 17th edition which I suspect they may not want to pay for.
The original work to be carried out was to reconnect the garage.
The 4mm swa is actually only to core.

So correct me if I’m wrong. I have to protect swa with 32amp mcb and rcd even if it is 100 mA time delay.
And at the garage fit a builders supply unit with a 30mA rcd and drop an earth rod. OR
Use a 32 amp 30mA rcbo at shop and fit a none rcd protected unit at garage?

[FONT=&quot]Also should I split tails (still got to put in small cu?) or just go for new split load board. I presume the cheaper is to split tails and forget shop?[/FONT]

 

[JUD]

Thanks Pushrod.
I was going to connect the garage earthing system to an earth rod at the garage, but thought not having the two earthing systems connected meant that the rcd's would have discrimination?
Also, I know the Swa is 3 core, but still only single phase and thought the reference method D would be a 37amp rating? (third core being used as earth)

Yes you are right , sorry was in a bit of a hurry when replying and didn't look properly

The SWA does not actually need rcd protection, if you can reposition the breaker on the first CU to a non rcd protected position that would solve that problem.

Did exactly the same thing myself in another thread. I went one further though and was looking at Reference Method C aswell as 3 phase column

 

[chloebear]

Bit confused on one thing - You mention that the supply is TT but with no Rcd protection. How can that square with the regs in any shape or form??????????

 

[optician]

Exactly, thats why it all needs updating. I can't see an RCD and the earth is to an earth rod. Here's the piccies you tell me.
Its in a small cupboard The pink coloured swa is unconnected, the earth cable you can see runs from the fuse board curls round the cupboard and then out to the rod making no other connections.