315A sub-main options

[pc1966]

A potential customer of ours was asking about having more power made available. Just now it is just a casual request and it looks like they want 9-10 * 32A TPN supplies so, say, 315A total. We can get that much easily from the bus-bar chamber around 100m away but from a moment on an on-line calculator:

• I am not relishing the prospect of wrangling 240mm cable in to a suitable MCCB board even with professional help.
• Maybe better to put in two 160A sub-mains and then 70mm and a pair of 250A MCB boards?
• Or three 100/125A supplies on 35/50mm to 125A boards?

Just to gather thoughts should it ever get to the stage of actually designing and costing it.

TL;DR How much parallelisation is sensible?

 

[David Prosser]

240mm seems a lot bigger than necessary for 315A 100m run.

 

[westward10]

What vd have you factored in.

 

[pc1966]

240mm seems a lot bigger than necessary for 315A 100m run.

It does seem a bit big, both Doncaster and Elan calculators give it though:

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However, data sheet for Prysmian would suggest 150mm in duct is good for 315A.

 

[pc1966]

What vd have you factored in.

Was looking at 3%, since final circuits will be short so easy to keep to 5%. No lights to bother with!

 

[LewisM]

reducing crimps in a trunking below the panel board?

 

[pc1966]

reducing crimps in a trunking below the panel board?

Certainly an idea. At one point I was also looking at sectored aluminium cable and then joints to something like tri-rated to make final routing easier.

 

[David Prosser]

It does seem a bit big, both Doncaster and Elan calculators give it though:

Welcome to Doncaster Cables - Technical Help

Doncaster Cables is the largest British owned general wiring manufacturer in the UK. We have been manufacturing cables since 1984 and among our current staff alone we have over 1000 years direct cable manufacturing experience. Throughout this time we have continued to develop in to an...

www.doncastercables.com

Cable Calculator - Cable Sizing & Selection | Eland Cables

How to find the size of a cable? Cable size calculator to aid specification of cables to British Standard BS7671 and International standard IEC 60364-5-52. Use the cable calculator to add your installation details for sizing guidance and cable type suggestions. Full technical support available.

www.elandcables.com

However, data sheet for Prysmian would suggest 150mm in duct is good for 315A.

It's all down to the installation method I suppose. For some reason I thought because of the mention of a bus-bar chamber it would be on cable tray.

 

[pc1966]

It's all down to the installation method I suppose. For some reason I thought because of the mention of a bus-bar chamber it would be on cable tray.

It can go through part of the building on tray/ladder, but probably at least a section of it to 30-40m would go underground in duct.

Just now I am thinking that 2 * 160A 70mm supplies (with 35mm CPC added in parallel to armour) would fit the bill, meeting 5s disconnect on the cable to 100m or so and also good selectivity with both main fuses and MCBs.

Still to find out what they actually want or if they are willing to pay for it! Having said that, the annual bill for power is likely to be far more than the installation costs...