size of cable for lighting outside swa!!!!!

[kingsleyclay]

Hi I want to no if I should run 2.5mm 3core swa 50+ metres long for outside post lights or can I just stick with 1.5mm? Another Sparkie said I should be using 2.5mm due to the length of the run the light are not going to be drawing alot so not sure

 

[m4tty]

What's the load of the lights ?

 

[SLIPSHOD & SLAPDASH]

Last year we ran some 35mm 3 core for a gate and a couple of low energy lamps.

 

[Zeespark]

Whats the metering and earthing arrangements as well Kingsley?

AndyGuinness

 

[Evans Electric]

As M4TTY says , you need to know the load . If it is 1000W 1.5 would do , just.

 

[SPECIAL LOCATION]

Hi I want to no if I should run 2.5mm 3core swa 50+ metres long for outside post lights or can I just stick with 1.5mm? Another Sparkie said I should be using 2.5mm due to the length of the run the light are not going to be drawing alot so not sure

Well if you are competent enough to do this work you will be well aware of the volt drop calculation tables...

and how to use them and calculate maximum permissible length for specific cable sizes......

BUT...

If you did know this..

you wouldn't be asking??? :C

If it were me I would be calculating the maximum current drawn multiplying it by the metres length of the cable..

and the mV/A/m tables....

I wouldn't be asking another spark who also hasn't got a clue...

as that is the daftest way to design any circuit that uses electricity....

I am assuming you have done your C&G's and they still do Volt Drop calculations??

Tell me what figures you think are permissible?

And I will then say if I agree?

 

[kingsleyclay]

Not sure what the lights are giving off yet but I think if I use 2.5mm 3 core then I should be way within my limits and it don't cost much more. I was worried about volt drop mainly. And if I have a wall mounted photocell I will need t+e in and out? Permanent live + neutral and the a switched line and neutral return?

Haha and yes I'm new to this mate just done my 2330 L3

 

[Manator]

Not sure what the lights are giving off yet but I think if I use 2.5mm 3 core then I should be way within my limits and it don't cost much more. I was worried about volt drop mainly. And if I have a wall mounted photocell I will need t+e in and out? Permanent live + neutral and the a switched line and neutral return?Haha and yes I'm new to this mate just done my 2330 L3

As you are new to this I will give you some advise. No electrical installation should be done by guesswork, to correctly design this circuit you need to know the basics of the supply, the demand you are designing for and the type of protective devise you intend to use.

If you work for a company as the majority of electricians do, then all these calculations are done for you and you just install what has been specified. If however you are responsible for the design then you have to do all the calculations yourself. I have all my design calculations on file for almost every circuit I do, sometimes I add continuation pages to my certificates with these calculations included, just in case some other electrician decides to question a size of cable or reference method used in the install.

There is a thread on this forum that shows how wrong it can get if the wrong size cable is used, in fact, the install does not work! Thats why guesswork should never play a part in electrical design. Use your notes from 2330 L3 and calculate the size of cable properly, and do not listen to someone who has guessed that 2.5mm will be needed.

 

[kingsleyclay]

Cheers mate sounds good I was thinking that well I only no that it is an mcb board. But I will have to do the calculations when I get more info on the weekend but when you are at college other students always say I will never use that but you don't realise you need it!

 

[ProDave]

I would only add, it's NOT always a good idea to over size cable "just in case" Certainly in the case of light fittings and sensors, you may find the terminals tight or impossible if you go up to 2.5mm

So find out the ratings of the lights and the cable length, do the sums, and IF 1.5mm is okay use that. You will find it makes termination easier.

Only go up to a larger size if the volt drop calculations say you need to.

 

[gavindrummond]

Hi I'm a student my self, but this may help.

Design outside lighting system.

50+ meters of cable run.

To maximise the it's usage you may want it on a sensor that way it's not on in the day.

Voltage drop comes in to play so we know 3% which is 6.9v allowed for lighting off a public supply ie: 230v.

Other factors

it - current carrying capacity.

In - rated protective device.

Ca - ambient temp.

Ci - rating factor for cables embedded in insulation although this should not apply.

Cc - rating factor depending on protective device or installation condition. You should get this info from the on site guide and be able to work all of these out from there.

 

[kme]

Hi,

Can I just add that is would be very helpful, to me at least, if you could manage some punctuation, at least now and again. I decoded your first post, but gave up when trying to make sense of:

Cheers mate sounds good I was thinking that well I only no that it is an mcb board

KME