New supply for garage, split from cut out

[Millo]

Good morning,

I've been thinking of the best way to supply my garage with a new fuse board from the cut out.

I've PME an new 80A cut out.

My thought is: split incoming with henley's, install a 50A or 63A dp switch near the cutout.

Use 2 core swa 10mm or 16mm to supply the new db. With a sperate earth stake in the garage and not connect swa in the garage db.
I'll use 10mm or 16mm earth to connect earth stake.

The run is 14M and I've a trench dug out. I don't want it in the main db. The main db is fully populated with rcbo.
I have 1 spare way but do not want to use it.

The garage db supplies the garage, shed and the conservatory at present.

The previous owner was a handy man.
I'll keep the circuits as is.

The garage board is a hagar with no rcd at present. Thought to change out the main switch or just full populate with rcbo.

Any concerns please?

Regards Millo

 

[kingeri]

If you do as you propose, how will the SWA be protected from overload/fault current?

 

[Millo]

The garage db will be supplied from the double pole 50A or 63A circuit breaker from the henley blocks. The main house db will be supplied direct from the henley's.

Safe isolation for garage db.
I could use a rcd with time delay and or 100mA for discrimination on the 30mA in the garage. But this might be a bit over kill. ?

Thank you for you help
Regards

Millo

 

[kingeri]

You mentioned a switch but not a circuit breaker or fuse.

 

[Millo]

Kingeri, your quite right I didn't.

The dp 50 or 63A will be the circuit breaker not just a dp switch.

This will be isolation and protection.what would you recommend? 63A MCB? Assuming the cables current capacity is higher.

 

[Andy78]

Kingeri, your quite right I didn't.

The dp 50 or 63A will be the circuit breaker not just a dp switch.

This will be isolation and protection.what would you recommend? 63A MCB? Assuming the cables current capacity is higher.

This should be worked out with your cable calculations. Are you an electrician ? I'm asking because this is posted in DIY.

 

[Darkwood]

Kingeri, your quite right I didn't.

The dp 50 or 63A will be the circuit breaker not just a dp switch.

This will be isolation and protection.what would you recommend? 63A MCB? Assuming the cables current capacity is higher.

Can we clarify you understand that a DP isolation switch does not give you overload protection here, your responses are somewhat ambiguous and do not give clarity on this point and the mcb comment seems to come as an afterthought following a response to your post. As you have not filled in your profile I need to try gauge your understanding through direct questioning of what may seem very condescending questions if you are fully qualified.
Is there any reason why you are isolating the garage from the main earthing arrangement, this would be a last resort given you have an excellent reliable PME system to utilise the earth from, are there any reasons you wish to install a less reliable method like an earth rod?

 

[Millo]

I qualified a while back, but wasn't clear in my write up.

I am looking to protect the SWA and to discriminate between the 2 db's.

There is no reason that I cannot use PME.
I didn't want to cause a posSible issue with the main db.

The cutout has only just been changed to PME a few days back, the system was TNCS.

I will fill in the profile section soon enough as I only joined today.

So 50A or 63A MCB depending on cable size.

Use the PME

Use rcbo on circuits in garage db

 

[kingeri]

Was TNCS? Now PME? PME is TNCS....or did you used to have PNB?

 

[Toneyz]

Where do you propose to install this 50/63A switch fuse ?.

 

[Darkwood]

Discrimination is normally referring to short circuit fault currents tripping devices not overload ratings and in domestic you will rarely achieve discrimination unless you have a 200amp supply so your responses are somewhat confusing, can you elaborate better on your design and why.

 

[Millo]

It was a TNS system. Seperate earth from the neutral.
Now its been linked in the new cutout.
TNCS or PME you are quite right.


All I would like to do is split the supply through henley blocks.

Direct connect the main db to the henley's.

Install a protective device in the meter cabinet for the new supply cable.


I do not have the cable, as I pointed out it will be either 10mm or 16mm SWA. Hence the 50A or 63A protective device (MCB)

Cable design has determined the max current. Hence 50A for 10mm and 63A for 16mm will be ok.

I'll install a 30mA RCD in the 2nd db or use RCBO.

 

[kingeri]

But what is your design current for db2?

 

[Octopus]

Op , how are you planning to comply with part p?

 

[Percyprod]

How can you split it at the cut-out? Surely you have a meter fitted, so you either split it after the meter or two meters.

 

[Millo]

The meter is the supply?
I wouldnt be allowed to split the cutout.
Only our supplier can do that I thought.

The Ib hasn't been worked out yet.
We are mid renovation and I'm undecided on supplies.

The db at present supplies the conservatory garage and shed.

This is the reason I'm asking for help.
The shed will have a hobby lathe, pillar drill, arc welder etc.

The garage will be a gym and house the tumble dryer.

The conservatory will use a 2kw heater at some stage.

So far, I know I need an MCB for overload, 3 core SWA using The PME.
The garage db need an rcd or each circuit on rcbo.

 

[Millo]

I think from this all is sorted.
Thank you all.

 

[Darkwood]

Your choice to use the pme earth is dictated by the nature of the outbuildings and any gas or water supplies they may have, I did query you as to why you opted for a rod with main earth isolation, it could be the case you need it and getting it wrong can make your installations unsafe... please expand on your choice and why?

 

[Millo]

The garage isn't Seperate it's attached to the kitchen. It houses water through plastic piping. Also the garage is wired in singles through metal conduit.

The shed is wooden with a tin vernier and a concrete floor.

Ok let's look it through your eyes, how would you install this?

I do need help with this please. Hence why I came on a forum.

 

[Darkwood]

Use your house earth for both garage and shed as long as the shed has no structural steel and metal incoming gas or water then fine to use your origin earthing system, if your tin shed has structural metal framing then I would still use origin earthing but appropriately sized for bonding as well as grounding a rod to omit any local PD between the Earth and natural ground.