Cable selection

[sparky147]

Im installing 3 phase sockets ib = 14amp, blue sockets ib = 13.04, 4 x sockets all installations will be on a radial circuit each circuit will be just over 60 meters installed in conduit using 2.5mm cable, the question is will the cable be big enough the the instalations or do i need to go up to 4mm

 

[Liamsparks]

Look in your OSG at appex 7 ( i think, or 6) this is the volt drop area. in here you'll be able to find the information to carry out a quick calculation.

 

[sparky147]

just want to make sure im dong it correct as im not 100% sure havent done the calculation in a long time any tips would be great

 

[malcolmsanford]

Where did the 2 Ib's come from ??

If you take the lowest Ib of 13.04 then 18 x 13.04 x 60 / 1000 = 14.08 then temp of x 0.923 = 12.99 so even without the temp co then the longest run would fail.

What are the sockets for ..............plug in portable equipment or fixed?

Have you thought about a ring main for the sockets. It maybe a better design solution, save taking up 4 ways in a DB. You could use smaller cable, only down side is a need to have a protection device at each socket

 

[sparky147]

i got the ib by watts / volts installing 2 x 16amp sockets each equipment being plugged in are 13.04 amps then im installing a 3 phase circuit 2 x 3 phase sockets the equipment being plugged in are 6amp and 8 amp then im installing 4 13amp sockets all equipment being plugged in is fixed cant install a ring main as i havent got enough room in the conduit would it be best to install all circuits in 4mm

 

[malcolmsanford]

IMO I would not be installing fixed equipment in a commercial/industrial enviroment via a socket and plug. Have you thought about switch isolators?. Far safer.

I always feel that someone can uplug a machine to plug something in and all kinds of problems ensue.

 

[sparky147]

im there on site at all times so no one will plug in other equipment but good point sould of thought of that

 

[Deleted member 26818]

I would suggest sizing the cables according to the socket rating.
You might also want to consider sizing them so that if in future you decide to increase the socket rating, you will not have to change the cabling (how often do things get changed round?).

 

[Engineer54]

i got the ib by watts / volts installing 2 x 16amp sockets each equipment being plugged in are 13.04 amps then im installing a 3 phase circuit 2 x 3 phase sockets the equipment being plugged in are 6amp and 8 amp then im installing 4 13amp sockets all equipment being plugged in is fixed cant install a ring main as i havent got enough room in the conduit would it be best to install all circuits in 4mm

Are you saying that you have installed a single conduit run to accommodate these circuits, before knowing what size cables you would be using?? Are you using the conduit as your CPC for these circuits, or pulling in a wired CPC??
So what are you going to do now, if your conduit size is now too small for the larger sized cables you obviously now require for these planned circuits??

 

[sparky147]

I have installed 2 25mm plastic conduit runs, in the first conduit run im planning to install 2 x 3 phase sockets and 2 x 16amp sockets each on there own circuit, in the second conduit run im installing 2 x 3 phase sockets and 4 x 13amp sockets each on there own circuit, using 4mm cable for all circuits, got enough room for a radial ciruit

 

[malcolmsanford]

I'm sorry sparky147 I don't like to keep picking holes in this, but can you tell me why you are installing 4 x 13amp sockets in 4mm all on their own circuit? Is there a reason for this. As I'm assuming they are 13amp BS 1363 sockets that will have a BS 1363 fuse in the plug top.

Also your going to have a fight on your hands trying to draw 2 x 3 phase sockets (10 x 4mm assume CPC is 4mm) and 4 x single phase sockets circuits (12 x 4mm assume CPC is 4mm) so a total of 22 cables in a 25mm conduit, with Bends and boxes.

 

[sparky147]

Thats fine, i have installed it in a way that only 10 4mm cables will be in the conduit at once as it splits half way through, also regarding the sockets the reason i wanted to run it on there own if there is a fault it will only trip out the sockets do you think i can get away using 2.5 for the sockets was just worried about the run as its 60 meters

 

[malcolmsanford]

As yesterday calcs the 60 meters will give you a volt drop of over 13 volts and so no, but as that is the furthest, you might get away with a couple of the shorter runs in 2,5mm.