3phase cable, what gauge/size?

[mechman]

Hi all.
Thinking of getting 3 phase 440 volt to my container, I have no idea about cable sizes. The run is 120 metres. At present it has 240 volt and the power drop is noticeable. Any advice is welcomed from those who know the dark art ( well it is to me) Which company is best for this kind of cabling? Probably 32 amp
Norm

 

[Bornfree]

Hi all.
Thinking of getting 3 phase 440 volt to my container, I have no idea about cable sizes. The run is 120 metres. At present it has 240 volt and the power drop is noticeable. Any advice is welcomed from those who know the dark art ( well it is to me) Which company is best for this kind of cabling?
Norm

For anyone to answer this they will need to know what load your intended to run.

 

[Matrixx]

Need distance, how it is contained, power required and size of breaker feeding the cable.

 

[mechman]

For anyone to answer this they will need to know what load your intended to run.

I'm thinking 32 amp.

 

[Matrixx]

quick check says 10mm 3 core SWA. thats with a 5% volts drop. Underground. @400 V AC.

 

[mechman]

quick check says 10mm 3 core SWA. thats with a 5% volts drop. Underground. @400 V AC.

Would above ground make a difference?

 

[brightspark]

quick check says 10mm 3 core SWA. thats with a 5% volts drop. Underground. @400 V AC.

he is wanting 3 phase supply and will require a neutral for the single phase so its 4 core

 

[Hotstuff]

If your SWA is serving a distribution board for both three & single phase circuits then you will need 4-core SWA which would also include a neutral conductor.

You quote a cable run of 120 Metres, but is that from the origin (electricity service meter) of your installation? This could have an impact on your cable size.

You need to also consider your earthing system.
If using the SWA sheath as a protective conductor, does the selected cable have a sheath of sufficient cross sectional area.

If you are using the service earthing system, it’s likely to be TNC-S so you could be exporting the supply neutral out to a metallic bodied container creating a hazard associated with potential differences.

You might be wise to consider a TT (RCD and earth rod) earthing system at the container.

If you are looking at a maximum load of 32 Amp per phase then you need to consider the fuse discrimination for your sub main which might be more like 40 Amp, but that would depend upon your loading.

To complete this installation job safely, there’s more to consider than just running the cable.

Edit: posted at the same time as @brightspark

 

[Brad93]

85 metres we have 25mm2 cores

 

[dobbslc]

If you're getting volt drop problems on the existing cable you'll need to increase the size weather 3 phase or single, being buried reduces the cable rating compared to "clipped direct" on a wall for instance. I'd also say a 25mm 4 core is probably what you need on a long run like that. Need to know about supply size and earthing system as well.

 

[hotponyshoes]

he is wanting 3 phase supply and will require a neutral for the single phase so its 4 core

Off topic:
Could you leave the existing single phase installation as it is and just install the 3ph along side?
(Presuming the kit that's suffering from the voltage drop on the 1ph will be moved onto the 3ph)

Also, off topic, if the existing 1ph cable was of a suitable conductor size could you just add a single core cable (or 2) ?

 

[brightspark]

to be honest its easier and cheaper just to put the 4 core in of larger diameter , minimum of 10mm giving about 5 kw each phase its best to go to 16mm that will give about 8 kw or 25mm if u can afford it

 

[brightspark]

what are your earthing arraingments back at source

 

[Erie Fred]

120 meters is quite a distance for something laying on the ground.
Might it be better to run PVC conduit and wire it with boxes at each end ?
Over here we use rubber "SO" cord for this type of exposed work, it is much more expensive versus what we pull into conduit "THHN" etc. wires.

I'm sure there are several code problems, and I don't have the proper terminology.

 

[brightspark]

its diffrent over here you can easily fit armoured cable buried or just clipped round the bottom of a wall layed on the deck or fence or even overhead using catenary wire

 

[mechman]

Some times I wish I'd studied Klingon.

 

[MetalMonkey]

120 meters is quite a distance for something laying on the ground.
Might it be better to run PVC conduit and wire it with boxes at each end ?
Over here we use rubber "SO" cord for this type of exposed work, it is much more expensive versus what we pull into conduit "THHN" etc. wires.

I'm sure there are several code problems, and I don't have the proper terminology.

We tend to use SWA (Steel Wire Armoured) over here which is designed for direct burial, or clipping or it can be used in ducts.
There are other ways to do it, but it is nearly always easier and more cost effective to just use SWA.

 

[mechman]

If your SWA is serving a distribution board for both three & single phase circuits then you will need 4-core SWA which would also include a neutral conductor.

You quote a cable run of 120 Metres, but is that from the origin (electricity service meter) of your installation? This could have an impact on your cable size.

You need to also consider your earthing system.
If using the SWA sheath as a protective conductor, does the selected cable have a sheath of sufficient cross sectional area.

If you are using the service earthing system, it’s likely to be TNC-S so you could be exporting the supply neutral out to a metallic bodied container creating a hazard associated with potential differences.

You might be wise to consider a TT (RCD and earth rod) earthing system at the container.

If you are looking at a maximum load of 32 Amp per phase then you need to consider the fuse discrimination for your sub main which might be more like 40 Amp, but that would depend upon your loading.

To complete this installation job safely, there’s more to consider than just running the cable.

Edit: posted at the same time as @brightspark

As I said, a dark art to me.

 

[mechman]

to be honest its easier and cheaper just to put the 4 core in of larger diameter , minimum of 10mm giving about 5 kw each phase its best to go to 16mm that will give about 8 kw or 25mm if u can afford it

Good reply, Haven't checked prices as I didn't Know what I needed. Or supplier.

 

[Misterg]

Haven't checked prices as I didn't Know what I needed. Or supplier.

Try these people for price. They were the cheapest I could find a couple of months ago when I needed some 10mm for my garage. Delivery, etc. was spot-on.

https://swacable.net/swa-cable/

They also do the glands / cleats, etc.

I think you need to get someone to look at your installation - if it's a steel (metal) container, you might need to have an earth bonding wire too (so that would be a 5 core cable).