New circuit design question

[GBDamo]

What load is going on the final kiosk? 70mm SWA, buried is good for 70ish amps @ 120m

All this 70 Amps may not be needed at the final kiosk, how many?

You may find you can run 70mm to the first two kiosks then 50mm to he final.

(Numbers not calculated, just to show the principle)

 

[RyanAspire]

Sorry guys, I mistyped at work! The RCD won't be at the intake, it will be at the first DB and then the circuit will continue from there via an MCB which will be downstream from this RCD.

Just for clarity I completely agree that 70mm should be the case all the way, i was just wondering if I was misinterpreting the regs or not.

The majority of the load will be at the furthest end of the install yes, but i am trying to future proof too incase they should want to add any other equipment at the other DBs.

Thanks everyone for the feedback though ?

However I'm considering the option of no RCD at the first and second DBs and use RCBOs and then one RCD at the final kiosk

 

[RyanAspire]

What load is going on the final kiosk? 70mm SWA, buried is good for 70ish amps @ 120m

All this 70 Amps may not be needed at the final kiosk, how many?

You may find you can run 70mm to the first two kiosks then 50mm to he final.

(Numbers not calculated, just to show the principle)

Yeah i considered that too as I think i calculated at 100m that 50mm would be fine. I had said this but they decided to go ahead and purchase the whole run in 70mm

 

[Lucien Nunes]

it will be at the first DB and then the circuit will continue from there via an MCB which will be downstream from this RCD.

Why do you want another MCB in line with the run of the distribution circuit? Its size is likely to be dictated by VD not current rating, so it won't need fusing down anywhere and therefore won't be affected by the RCDs in the DBs.

 

[RyanAspire]

Why do you want another MCB in line with the run of the distribution circuit? Its size is likely to be dictated by VD not current rating, so it won't need fusing down anywhere and therefore won't be affected by the RCDs in the DBs.

The size is definitely determined by the VD. I don't want an issue downstream i.e cable damage to take out the intake fuse?

If there is an issue at the end of the mobile home on the SWA that isn't protected via MCBs along the way then I don't want the fault path to go all the back and blow the 100A fuse that UKPN will then need to come and replace at cost and downtime without power too. At least via this route the power upstream should remain intact and also help to identify the location of a fault too

 

[westward10]

What design current are you basing the vd on.

 

[richy3333]

Also, I'm sure i know what the answer is to this one....the supply is TNCS for reference, but I won't need an earth rod for caravan will I? I'm not looking to create a TT system or PME unless it is beneficial/regulation.

ESQCR prohibits the use of PME for pikey vans. Start banging those rods in!

 

[Spoon]

The size is definitely determined by the VD. I don't want an issue downstream i.e cable damage to take out the intake fuse?

If there is an issue at the end of the mobile home on the SWA that isn't protected via MCBs along the way then I don't want the fault path to go all the back and blow the 100A fuse that UKPN will then need to come and replace at cost and downtime without power too. At least via this route the power upstream should remain intact and also help to identify the location of a fault too

Ok, so if I understand this correctly, Kiosk 1 is purely for the incoming supply, so main fuse and meter?
From this kiosk, you are going to supply CU's in each of the other kiosks? If this is true then the supply is much longer than 3 meters so you will have to fit a fused isolator.
Again mate, as I asked in post #2, what power requirements are needed for each kiosk?

 

[RyanAspire]

Ok, so if I understand this correctly, Kiosk 1 is purely for the incoming supply, so main fuse and meter?
From this kiosk, you are going to supply CU's in each of the other kiosks? If this is true then the supply is much longer than 3 meters so you will have to fit a fused isolator.
Again mate, as I asked in post #2, what power requirements are needed for each kiosk?

Kiosk 1 incoming from UKPN with meter and fused isolator as you say
Kiosk 2 ring main circuit and lights
Kiosk 3 ring main circuit and lights
Kiosk 4 provide power for mobile home

All of these are subject to potential increase in the future, not sure what and when, that will obviously be decided at a later date but its good to make sure it is there and possible to do in the future. Its all minimal power required except for the mobile home for obvious reasons. I wouldn't want to drastically reduce the cable size downstream for the reason of future proofing, my question was purely based on curiosity of the regs.

Each of the kiosks besides the first will need RCD protection because there are final circuits which will all be outside. We have also established that 70mm is correct as i had spec'd (this was just a query to understand if i had misinterpreted the regs).

But one of the reasons we seperate circuits is for the same reason, so one issue doesn't take out everything else, hence I want to put the supply on MCB at each kiosk, to avoid that happening. Do you feel this is wrong and if so, why?

Just trying to see everyone's views on it and what reasons they would have to disagree on that too. We're all here to learn ?

 

[westward10]

We haven't established 70mm is correct as we do not have enough information. So the supply to the kiosks from kiosk 2 will be rcd protected?