Garden workshops/Shed supplies

[Deanosss]

Hi All,

I’m looking for a bit of advice with regards to a clients outdoor workshops.

Would the diagram attached be a acceptable method of installation? One supply from the house into a DB (RCD protected Garage unit) in the first workshop then a supply from there into the second workshop with DB and both with a TT earthing system (DNO is TNC-S supply)

 

[Spoon]

Welcome to the forum mate.
Boring bit first before the question. This work falls under Part P and is notifiable.

What earthing arrangement is your house supply?
Why TT the supplies to the garage and workshop 2?
What's the length of runs?
So you have a 25A breaker in DB1 that will feed DB2. What size breaker are you using in DB2 to feed DB3?

 

[Deanosss]

Cheers Spoon ?

The House supply is TNC-S and I would be looking to upgrade the current breaker in DB1 to a 32amp supplying DB2 then 0ver to DB3 with a 20amp.

DB2 is 5mtrs away from DB1 and DB3 is 7mtrs away from DB2.

I hope that all makes sense

 

[buzzlightyear]

The House supply is TNC-S and I would be looking to upgrade the current breaker in DB1 to a 32amp supplying DB2 then 0ver to DB3 with a 20amp.

DB2 is 5mtrs away from DB1 and DB3 is 7mtrs away from DB2.

and what size cable would be used from DB1?

 

[telectrix]

and what size cable would be used from DB1?

a round one.

 

[Deanosss]

and what size cable would be used from DB1?

Hi Buzz, 6mm SWA

 

[Spoon]

and what size cable would be used from DB1?

Hi Buzz, 6mm SWA

Says 6mm in his pic mate. Right at the bottom.

 

[Spoon]

Cheers Spoon ?

The House supply is TNC-S and I would be looking to upgrade the current breaker in DB1 to a 32amp supplying DB2 then 0ver to DB3 with a 20amp.

DB2 is 5mtrs away from DB1 and DB3 is 7mtrs away from DB2.

I hope that all makes sense

Curious at to why TT the buildings?
I take it that there are no extraneous conductive parts in either building?

 

[buzzlightyear]

Says 6mm in his pic mate. Right at the bottom.

just seen it on the the bottom of the plans .

 

[Deanosss]

Curious at to why TT the buildings?
I take it that there are no extraneous conductive parts in either building?

I didn’t see any in either of the buildings and I did check for pipe work etc from the house entering them. I was thinking more of the DNO supply being PME and if a break in the Neutral/Earth was to occur…..but I guess I’m over thinking that.

 

[telectrix]

.but I guess I’m over thinking that.

you are. lost N is very rare, could be a problem if outbuildings are made of metal, otherwise, us the existing earthing system. the low Zs values outweigh the risk of lost PEN.

 

[Mikegh]

You'd be keeping each of the 3 boards rcd protection independent of the other boards

You don't want any fault in one building tripping RCDs in another , basic sensible design

 

[buzzlightyear]

You'd be keeping each of the 3 boards rcd protection independent of the other boards

You don't want any fault in one building tripping RCDs in another , basic sensible design

i dont believe you

 

[James]

6mm 3 core?

If you are intending on making the outbuildings TT then why not use 2 core?

with the cost difference, you could then run 2 x supplies from db 1 and supply each building with its own breaker.

 

[pc1966]

If they are to be used as workshops I would also suggest some emergency lighting in case power fails for any reason. The sealed LED baton style lights are often available with emergency battery back-up built in.