Design Info.

[danny124]

Hi guys, after getting valuable info from previous thread and study my notes. After flicking through the BS book, and OSG i think i finally have my design iformation, for my assessment using my grandads shed/workshop as a rewire


If you guys could check it for me, i would be very grateful. And if your ever in the Biggin hill area, I buy you a beer for your time...haha

Right here goes:-


Circuits

Lights:- 2x 36w Florescents = 72watts
x factor for control gear lights 1.8
= 130watts (0.57amps)

Diversitiy of 66% = 0.38 amps. (will use a 6 amp MCB for this circuit)

Planer supply:- (Not to be installed but adding in calculations if added for the future)
This isn't working at the moment waiting for a new part for it. But its a 10amp
machine, but has a 23amp start up.

Diversity 100% = 32amps

Ring:- Consists of 4 sockets, with be running general electric tools, but in winter times may have
heaters to keep the old boy warm while he does his hobby stuff.

Diversity 40% = 12.8amps


Total Demand (max demand) = 45 amps (So will have a 63a RCD Main Switch 30mA)

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It will have 2 conduit runs in PVC in stranded cable (Method B),
1 for Lighting 8 meters
1 for Ring 20 meters

Lighting = 1.5mm (L&N) 1.0mm (Earth)
Ring = 2.5mm (L&N) 1.5mm (Earth)

Lights:- Table 4D1A

CCC = 1.5mm Method B 17.5amp
VD = 29x0.38x8/1000 = 0.08v (0.03%)


Ring:- Table 4D1A

CCC = 2.5mm Method B 24a (i see this as ok as its 20 amp per leg)

VD = 18x26x20/1000/4 = 2.34 (1%)

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Submains

25 metre run from under stairs in house, buried under lawn to shed, to cope with a Max deman of 45amps.

Be Thermoplastic 70degree armoured 16mm 3 core cable

Using table 4D4A and B

Say im using a 50amp isolation switch (over 3 metre rule) to cope with Max demand of 45 amp

CCC = 78A
Factors = Ca 1.00
Cg 1.00
Ci 1.00
Cc 0.90 (factor for burial of cable out of OSG)

= 78a x 0.90 = 70 amp (so good enough for 45 max demand)

VD = 2.4x50x25/1000 = 3volts (1.3%)


Plus adding the submain VD of 1.3 and my final circuit for my lighting 0.03%. All in all im well within the 3% Limit.


IS THIS RIGHT. OF HAVE I MESSED UP....

Sorry about the long read...

Thanks again guys

 

[philip962]

Don't forget it has to be swa cable in the garden

 

[danny124]

I put that in there mate.... Armoured cable...

Thanks for reading it Philip, Apart from that does it all look ok

 

[JUD]

Seeing as the VD on your lighting is so low, I think you could probably get away with 10mm² SWA (CCC = 58A x 0.9 = 52A)

4.4 x 50 x 25 ÷ 1000 = 5.5V (2.39%)

Lights.......5.5 + 0.08 = 5.58V (2.42%)[Max 3 %]
Ring.........5.5 + 2.34 = 7.84V (3.4%)[Max 5%]


Just need to work out voltage drop for planer. If it comes in at under 5% you're good to go.

Saves you a bit of money on the armoured cable.

 

[Doug]

You haven't mentioned:
cable size for supplying planer
circuit protection for distribution circuit

You're obviously exporting the earth. Presumably you've considered:
earthing type
checking main earthing & bonding
presence of any extraneous metalwork in shed

16mm is a heavy duty supply for a garden shed.

Are you coming from a spare way in the house CU or splitting the tails with a Henley type block?

Do you have any manufacturer's spec for the supply to the planer? Would it be better to have a lower rating of MCB, but type C or D?

 

[danny124]

Hi guys, managed to get some Specs on this planner...

its a 2 horsepower machine (1490watt) = 6.4 amp
But the spec manual says that its running power is 10amps and start up power pulls 23amps. It can go on 32amp supply, so i used 100% of diversity to make sure its covered.

Thats all i know.

The planer is about 1.5m from the DB. Cable size probably 2.5 to 4mm



The submain supply will be on its own isolator switchgear 50amp. splitting into henley block as house has old installation.

I have a TN-s system

Shed/workshop is made of wood but its big


regarding the 10mm JUD, the figure you got is clipped direct, and 3 phase. im single phase, and cant clip it to anything so got to bury it.
so if i use SWA 10mm ccc = 60a x0.9 = 54amps VD = 4.4 x 50a x 25m = 5.5v (2.4%)

So 3core 10mm SWA would be fine you reakon.

 

[JUD]

regarding the 10mm JUD, the figure you got is clipped direct, and 3 phase. im single phase, and cant clip it to anything so got to bury it.
so if i use SWA 10mm ccc = 60a x0.9 = 54amps VD = 4.4 x 50a x 25m = 5.5v (2.4%)

So 3core 10mm SWA would be fine you reakon.

Yer, me looking at the wrong column again

As you said 10mm² can still carry 54A buried and all VDs are within limits so I would go with that.

How are you terminating your SWA? Remember it needs earthing at supply end.

 

[danny124]

hey Jud, dont worry always looking in wrong places...

What ever size im using SWA and 3 core.

cheers

 

[danny124]

Hey Jud, sorry for late reply... Im terminating in Metelclads at each end, to supply submain going to use a wylex 1361 cartidge fuse metalclad board, and in shed also a wylex DB metelclad. Im using 3 core using the 3rd core as the CPC, just want a nice solid earth, but will terminate armour on gland and bango system with fly leads to pick up protection.

Also changed the spec a little by changing the ring to 2 radial circuits, just to split up the sockets and it was easier to run the conduit system that way too....