Suitable cable to carry 240V 250mtrs??

[DullChimp]

I am just about to start a barn conversion so my family and I are going to be living in a static for the duration of the build, unfortunately this is 250 meters away from the nearest power supply, I need some advice on what cable to use, I will obviously need some hefty armoured stuff but what size (mm), my requirements are listed below.

Voltage: 240
Ampage: 60 (thnx for the correction JohnD)
Distance: 250 meters (820')
Power consumption item list: lights, fridge freezer, washing machine, tumble dryer, electric kettle, 2 standard room heaters (in winter), microwave etc.

I don't think that I have left anything out

Thanks

P.S. No access to 3 phase

 

[JohnD]

"washing machine, tumble dryer, electric kettle, 2 standard room heaters "

these devices use about 13A each so I think your max load est is wrong.

Homes are usually rated at 60A to 100A

No electric shower or cooker, I hope?

 

[plugwash]

very big for a 60A circuit at that distance you are talking something arround 100mm^2 (don't have exact figures to hand). Terminating that cable will be a pita too.

60A is probablly overkill IMO, but even at a 40A rating the cable is still going to end up pretty big.

Is the supply in the barn three phase? If so it may be worth using a three phase feed to the caravan and spreading the load between the phases.

 

[Cremeegg]

Havent got my OSG to hand but TLC's website voltage drop calculator (that hasnt been updated to 17th edition standards) shows you limited to 3Kw maximum load using 16mm SWA. At around £1000 for that length of 16mm SWA cable its time to move the static.

 

[Steve]

It might be cheaper to hire a generator.

 

[GaryMo]

Agree with Plugwash, a 95mm SWA buried will give you a 63A over 250 meters.

 

[JohnD]

£££££££££££££££££

 

[GaryMo]

£££££££££££££££££

Wouldn't it just!

I really haven't a clue on the price of 95mm 3 core but taking a wild guess (probably miles out) at £25 per meter, he would be looking at £6250!

 

[Spark123]

Why use a 3 core as opposed to a 2 core?

 

[GaryMo]

If it's standard PVC SWA then 2 cores would be fine but not if it's XLPE.

//www.diynot.com/wiki/electrics:earthing_supply_types_and_bonding:swa_earthing

If I'd have put 2 core somebody would have replied asking what if it was XLPE being installed

 

[Spark123]

Yep, I remember writing that wiki article
XPLE may still may pass if using the adiabatic equation

 

[GaryMo]

Did you? Great article, very useful for a no-frills answer.

 

[JohnD]

I was wondering about an overhead supply, single cores
Sell the copper for scrap when the house is ready

Or a pole mounted transformer at the site, from the power co? I used to have one of those when I lived at IP8 3HF

Best of all, I agree, move the caravan

 

[toasty]

If it were me (which it isn't) I'd be tempted to go for a reasonably sized cable (say 25mm^2) which can easily handle the current required and say **£&" it to the slightly higher voltage drop.

***PLEASE NOTE THIS ISN'T MEANT AS ADVICE, JUST WHAT I WOULD DO, AND MAY NOT EVEN BE SENSIBLE***

I still don't understand (and this may well just be my ignorance) why a house can have a huge span of overhead or underground supply cabling well under the 100mm^2 or so discussed in this thread, but once it gets past the meter you have to limit the voltage drop to less than 4%

Why though? When the mains supply can fluctuate by some -6% or +10% i.e 207v to 253v.

Surely if your supply (like mine) is on the high side of this and doesn't drop off with load (either your load or that of others) then why can't you make an educated decision to have a slightly higher voltage drop on the other side of the meter?

In my case ~243v, I could theoretically afford a comfortable 20v drop and still be well over the 207v minimum (not to mention that someone on 207v can still have a 4% drop aswell, so would be under 200v). 20v drop would mean I could use 25mm^2 for a 60amp load over 250metres.

I'm sure someone will tell me it's not allowed (which I know) but why? Noone would really run 100mm^2 for 60amps would they, most of the time this supply would only be running at a fraction of this, during periods of high loads, big deal if the lights dim a little!!

Cheers
-Dan

 

[GaryMo]

Why though? When the mains supply can fluctuate by some -6% or +10% i.e 207v to 253v.

ESQCR Regs 2002
Supplies must be maintained within the range 216.2 volts to 253 volts, corresponding to a nominal value of 230 volts, minus 6% to plus 10%.