3 Phase Supply

[J2ay]

I have a 4 core 25mm SWA, running at a length of 110 meters, clipped direct to the wall on its own, needed for a 3 phase 400v supply.

Is it true that I would need to run a separate 16mm earth with it.

Also what size main breaker would you suggest i think 80amp.

any help on this would be much appreciated.

 

[ProDave]

The SWA is often okay for the earth, but this brings us to the discussion of what earth you have, where are you exporting it to and is it okay to do that?

You also need to look carefully at the voltage drop over that length.  That will probably be the determining factor that tells you the maximum load, not the current carrying capacity of the cable.

You seem to be designing this backwards.

Normally you work out the load requirements and then choose what cable will do the job taking into account current carrying capacity and voltage drop.

you seem to have a cable and now want to design the installation around the cable you have.  What if the volt drop calculations tell you the allowable load is less that what you are planning to connect to it? I haven't looked it up, but my instinct tells me that cable over that length will not be good for anything like 80A

 

[Blue Duck]

Definitely backwards

 

[Andy™]

I have a 4 core 25mm SWA, running at a length of 110 meters, clipped direct to the wall on its own, needed for a 3 phase 400v supply.

Is it true that I would need to run a separate 16mm earth with it.

Also what size main breaker would you suggest i think 80amp.

any help on this would be much appreciated.

depends what your circuit design / calculations say

im not doing them for you, however 80a at 110m on 25mm sounds wrong

i hope you are not an 'electrician' charging a customer for your 'knowledge / competence'

 

[M107]

This sounds like diy project

"I've been given some 25mm swa & now I've found a use for it."

You need to do some calculations first.

 

[Andy™]

TP isnt really 'a DIY project'

 

[matt.leung]

also good luck finding 110m of swa in one go... think you may need to join it, last time i checked the max length was 100m.... How are you planning to join 25mm swa???

 

[Andy™]

i could easily get 110mtr of it. likes of UK cables get it on drums with a few km on, they just cut what you want and load in onto a smaller drum. just because screwfix & co only sell in 100mtr max doesnt mean its not available elsewhere

 

[matt.leung]

actually i totally forgot about Batts cable, they are local'ish to me as well...... 

 

[Blue Duck]

Ill sell you 1000meters of it on one roll if you have the cash - its available in as long a lengths as you can handle

Not sure national rail would like that....

:slap

 

[steptoe]

My wholesalers can usually do 500m at a time, longer lengths to order, usually within a week, 2-3days norm.

 

[Andy™]

for cable, i skip the wholesaler and go direct to UK cables. much cheaper, and depending what i want, they will usually have it ready within a few hours. and they are local

 

[Andy™]

Very similar, but i wish they really were my 'local corner shop'

 

[kerching]

I just popped in there tonight on the way home.....got brother in law a wiha screwdriver set and snips 19 plus VAT, got a few bits for a job next week and had a brew and natter with the counter manager

Just passing through

 

[Andy™]

Kerch wouldnt do such a thing!

 

[M107]

also good luck finding 110m of swa in one go... think you may need to join it, last time i checked the max length was 100m.... How are you planning to join 25mm swa???

:slap msl1: msl1: msl1: msl1: msl1:

 

[J2ay]

The SWA is often okay for the earth, but this brings us to the discussion of what earth you have, where are you exporting it to and is it okay to do that?

You also need to look carefully at the voltage drop over that length.  That will probably be the determining factor that tells you the maximum load, not the current carrying capacity of the cable.

You seem to be designing this backwards.

Normally you work out the load requirements and then choose what cable will do the job taking into account current carrying capacity and voltage drop.

you seem to have a cable and now want to design the installation around the cable you have.  What if the volt drop calculations tell you the allowable load is less that what you are planning to connect to it? I haven't looked it up, but my instinct tells me that cable over that length will not be good for anything like 80A

No I have had a quote of an electrician ,

He gave me a load of information and I just thought I would check it. He hasn't bought the cable yet I just wanted to make shore as the quotation isn't the cheapest and he seems very young. 

 

[NozSpark]

Well 110m of 25mm 4 core swa ain't going to be cheap

 

[Blue Duck]

Its more like 35mm2 assuming the ze and not knowing the job

25mm£8/m 35mm£10/m ish plus delivery :|

 

[ProDave]

No I have had a quote of an electrician ,

He gave me a load of information and I just thought I would check it. He hasn't bought the cable yet I just wanted to make shore as the quotation isn't the cheapest and he seems very young. 

So tell us what you are planning to connect at the end of this cable and we might be able to tell you if it's any good or not.