A little assistance

[Spudnik]

Chaps,

Need to do a quick calc, but havent got my regs to hand.

I have a 3kW 230V supply to run 400M underground to an outbuilding.

Thinking 2 core SWA TT'd.

I have a suspicion that 25mm will not be large enough but cant confirm it.

Would someone be good enough to work out what size i need.

Ta

 

[xraytek]

Hi Jason,
I havent done the calc, but what I do have is a very handy excel spreadsheet that does all the calcs for you.
It even has a tab that does the adiabatic equation

CABLE_SIZING_SWA.xlshttp://rapidshare.com/files/331383789/CABLE_SIZING_SWA.xls.html

I got hold of the spreadsheet a couple years ago so have forgotten who I need to thank for it.

 

[Jimmyb]

25mm @ 13amp gives a vd of 9.1volts

35mm @ 13amp gives a vd of 6.5volts

50mm @ 13amp gives a vd of 4.84volts

hope this helps

 

[MarcT]

If my calcs are correct, the answer is 70mm (XLPE)

 

[ian.settle1]

What is it your supplying and is there any chance in the future extra loads will be added to the circuit?

How is the cable being run overhead/underground?

Just a few questions you need to ask for cable calc

 

[Darkwood]

Aint it gonna be cheaper to move the building closer

 

[Des 56]

16mm will have a little too high voltage drop,but perhaps consider that the tabulated values will be based on a higher operating temperature than the small load on a much higher current carrying capacity cable which will run cooler than the tabulated calculation
If the load is not to be increased in the future a 16mm may even be within capacity,so in this situation 25mm may be more than adequate

How to calculate without the tabulated values I dont know though,so yes maybe better to move the building closer

 

[Spudnik]

Ok, just been to look at the job and well, hmmmmmm.

Its a fishing lake that has just had installed a 100A cutout in a surface cabinet with no earth connection (its out in the sticks), but this has been mounted on 2 scaffold pole sunk in the ground.

I then have to get 400M to the porta cabin that is going to have 2 airators - one 500W & one 750W, a kettle, a fridge and maybe a freezer, a few sockets and a couple of flourescent lights. Heating is not going to be used as its only open in the summer months.

The two airators will only operate at between 2 & 5AM as this is when the oxygen levels are at the worst.

Therefore, somehow i need to install a small CU in the cabinet along with a suitably rated MCB for the sub main.

The SEB quoted 20K for the supply installation & the submain!!!!!!!

 

[gaz101]

Re: A little assistance hope this helps

Cable TypeArmoured Cables (90°C XLPE)
Supply voltage (V) 230
Phase:Single phase
Cable load (kVA)3
Cable length (mtrs.)400
Ambient temperature (c)30
Average efficiency1.00
Power factor1.00
Cable grouping factor1.00
Temperature correction factor1.00
No.of circuits:1
Maximum allowed volt drop (%)5.00
Selected installation MULTICORE SWA DIRECT/UNDERGROUND (IEE Table 4E4A Method D)
Cable Requirements.

Cable size (sq.mm):25.00
Max. current rating over 400 mtrs. 15.13
Actual voltage drop over 400 mtrs.9.91
Estimated conductor temperature (c)30.76
hope this helps gaz




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[MarcT]

I just realised my mistake, i used 5v instead of 5%, oops, thanks gaz.

 

[Spudnik]

Thanks for all the help chaps.

Looks like 25 will do the trick.

 

[YTSOxford]

Thanks for all the help chaps.

Looks like 25 will do the trick.

Good luck with all that digging Jason!

 

[bugsy]

Thought about installing a generator

 

[Spudnik]

No i wasnt gonna dig it!

There was a contractor on site with a digger!