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And the sand wont be cheap! 200m at 200mm thick (100mm below cable and 100mm over the top) and say 200mm wide trench = 8cu m (8 builder bags worth)!
Yikes!

Just looked at that on some web site. Even at 5cm surround (10cm x 10cm) it is saying 5 bulk bags at ~£50 each. Going to a safer/easier to pour in 20xm x 20cm (i.e. 10cm safe margin) it is 4 times that and almost £1,000

Might be cheaper to look at 90mm or 110mm twinwall duct? 200m of that is around the £400 mark.
 
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Agreed but the OP is being a bit coy as to what the cable is being used for. Assuming a mixed load it 'should' still meet 3% guideline if only 1A of lighting!
Well the regs still say that but really it is a hang-over from the days of filament lamps and their significant voltage/illumination sensitivity.

I personally would be OK with 5% drop on "mixed" if it is LED lighting. Which it almost certainly would be.
 
From here it has the light versus voltage law for halogen lamps as more or less cubic (V^3):

LED lamps are more or less linear output with V if a simple current-limiting resistor is used, even less sensitive if some DC-DC coveter/driver that regulates the output.

So best-case LED cares not as long as in-specification, worst case LED is 3 times less sensitive to small changes in voltage (i.e. if 3% limit VD for halogen lamp, then LED equivalent is around 9%)
 
Well the regs still say that but really it is a hang-over from the days of filament lamps and their significant voltage/illumination sensitivity.

I personally would be OK with 5% drop on "mixed" if it is LED lighting. Which it almost certainly would be.
I probably would too which is why I put 'should' in ' ' and guideline, and is justifiable if not filament/discharge lights.
I would probably aim for 4% though which would limit the OCD to perhaps 10A for 10sqmm!
 
I would probably aim for 4% though which would limit the OCD to perhaps 10A for 10sqmm!
I'm not sure I would bother with lowering the supply OCPD, it just has to be able to provide overload & fault protection for the SWA.

R1+R2 is going to be about 0.94 ohms for that run of cable, assuming 0.8 ohm as max Ze for TN-S then you are looking at max MCB of something like a 20A B-curve, or a 25A BS88 fuse if it is a sub-main (i.e. with 0.4s disconnection and and RCD planned for the far end, etc).

Ultimately what matters is the OP/customer is not needing load(s) much above 10A or anything with very big start-up surges!
 
OP might have a happier time by installing 2 x 6mm in parallel, 10mm singles..... etc
There are so many alternatives available after a little maths!
 
10A supply requested to supply comms kit. Not sure what exactly!
Probably a bit excessive but that is what asked for.
A lot of comms kit is 48v, years ago when I did a lot of comms rigging one of the new build remote masts had a temporary 12 KVa generator while the customer negotiated a sensible price for a supply from the DNO the hire company wanted to do some planned maintenance on the generator and needed to take it offline, I had the whole mast comms running off a 750w generator while they did the maintenance work
 

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