2 CUs on 2 Floors

[andyh]

Just starting to design an installation for my new build domestic dwelling. There are quite a few circuits and a lot of termination in the loft for audio/visual equipment, central lighting control etc. The house has three floors including the loft floor. I've been given advice to have two CUs, one on the ground floor where the supply enters (PME) and one in the loft 'plant room'. This will also reduce the cable runs as circuits on the loft floor, and possibly first floor, don't have to be run back to the ground floor. All circuits will be on individual RCBOs. More expensive but think it's the best option. The query is how to wire the two CUs together or whether to have separate supplies to each.

My first thought was to use 16mm2 SWA to connect the two CUs together but not sure whether to take this from the ground floor CU or have a separate connector block which would split supply to each CU.

The second option was to use standard 16mm2 T&E from a 60A RCD in the ground floor CU up to the incomer in the loft CU. This would be a neater install but not sure whether it's the best option.

I also have 4 SWA supplies from external buildings coming into the ground floor CU. I was intending using a metal CU for this as it would be stronger and easier to terminate.

Anyone any other suggestions on connecting the two CUs? Any recommendations on CUs to go for?

 

[Notsosmart]

Personal preferences will abound Andy so you may well get numerous different answers.

For what its worth my penny's worth is;

I would wire the Consumer units seperately that way you get maximum seperation of circuits, especially if you are bringing other external supplies in to the lower board. Also with seperate main isolators then you won't be losing power to both if modifications are required to one.

As to makes of CU they are all much of a muchness, depends on your budget really. (You get what you pay for ~ you also pay for the name)

(Sorry Not very helpfull really)

 

[bugsy]

Treat the top floor as sub main from ground floor board via MCB and put rcbo's on top floor board.
Run 16mm swa , to metal clad C.U. or metal adaptable box adj. insulated C.U.

 

[Spudnik]

Personally i would keep all the CU's in the one location, nearest the intake.

Having said that, i havent seen the job, so could very well change my mind once i had seen it.

If i did, i would go with Bugsy's method, using Hager.

 

[andyh]

Thanks for replies.

There are various reasons for having two CUs. Out of interest why would people prefer only one? Having two in my case reduces cabling hence cost. It also means less cabling in each CU and therefore makes for easier install. In addition we have three floors of UFH which means cables can only route between floors in one area. Having two points of connection means easier routing and less cable. Finally having two CUs means easier future circuit provision with two possible connection points.

Any disadvantages of the proposed system?

I had been thinking of using Hager. All circuits will also be on individual RCBOs.
Thanks for the input so far.

 

[marksparky]

hi andy i personally wud wire 2 seperately and prob use 16mm split concentric easier worked with than armoured

 

[pennywise]

I would have every floor on a seperate CU including one at the intake with RCBO's and individual SWA feeds from a ryefield unit at the intake position.

 

[lamb]

I would have every floor on a seperate CU including one at the intake with RCBO's and individual SWA feeds from a ryefield unit at the intake position.

I would have the same, with an Isolator before the Ryefield board.

Or for a cheaper option, Meter>Isolator>Henley Block> then on to
1) Ground Floor CU - Dual RCD or High Integrity
2) Switchfuse for Submain to Loft
3) Metalclad Board (Non RCD) for external SWAs