cable size

[Oxia]

In another thread I have been talking about a cable run to a chicken shed about 60-70m away from a house. I am now laying the cable my self to save costs. I have been told that it would need to be 6.0mm 2 core XLPE to provide a 30A supply to the shed but when I use ANY of the online cable size calculators they all suggest a min of 10.0mm cable....

Can anyone verify?

 

[leeco]

60 to 70m is quite a distance.

Try this site to calculate volt drop.

http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

 

[bernardgreen]

Voltage drop for 70 metres of 6 mm at 30 amps is 16 volts, that is 7% of the supply voltage. That drop exceeds the maximum permitted.

http://www.batt.co.uk/upload/files/currentratingsandelectricaldatabs5467_1352477469.pdf

Look at the right hand column

"Volt drop single phase AC touching mV/A/m "

 

[riveralt]

In another thread I have been talking about a cable run to a chicken shed about 60-70m away from a house. I am now laying the cable my self to save costs. I have been told that it would need to be 6.0mm 2 core XLPE to provide a 30A supply to the shed but when I use ANY of the online cable size calculators they all suggest a min of 10.0mm cable....

Can anyone verify?

One must assume that the person who told you that you needed this size cable has done the calculations for you. Shouldn't you be asking them this question - since they will be the ones signing the installation of?

A quick verification with them will save you having to dig the whole lot up again.

 

[JohnW2]

Voltage drop for 70 metres of 6 mm at 30 amps is 16 volts, that is 7% of the supply voltage. That drop exceeds the maximum permitted.

Indeed, and 70m of even 10mm² cable would have a voltage drop of 9.24V at 30A, which, at 4%, would still exceed the maximum permitted drop if there were any lighting involved - it therefore sounds as if 16mm² might be required.

The OP certainly needs to discuss this with his electrician, if a lot of wasted money and effort is to be avoided!

Kind Regards, John

 

[ban-all-sheds]

I am now laying the cable my self to save costs.

Laying, yes.

Providing, no - that will cost you money, not save it.

I have been told that it would need to be 6.0mm 2 core XLPE to provide a 30A supply to the shed but when I use ANY of the online cable size calculators they all suggest a min of 10.0mm cable....

Can anyone verify?

Yes.

Your electrician.

NO ONE ELSE.

 

[ericmark]

I have in the past laid cable where I knew the volt drop would be exceeded and used HF florescent units rated 200 - 250 volt to cope with volt drop.

Strictly speaking it does not comply but also I knew it would work.

Any on site electrician may after talking with you and doing a mental risk assessment seeing what you have may be willing to cut costs and use some thing not strictly complying but good enough for your needs.

However if he finds out you are telling everyone what he is doing on a forum he will likely change his mind and work to the letter of the regulations. This includes the depth you need to bury cable.

(i) Cables shall be buried in the ground at a depth of at least 0.6 m with added mechanical protection
(ii) Cables in arable or cultivated ground shall be buried at a depth of at least 1 m

 

[riveralt]

(i) Cables shall be buried in the ground at a depth of at least 0.6 m with added mechanical protection
(ii) Cables in arable or cultivated ground shall be buried at a depth of at least 1 m

Which regulation is this?

Okay found it myself.
705.522 (agricultural premises)