Armoured Cable

[tazzatime]

Going to be installing a 500watt Halogen some distance from the house.

Got access to a digger tomorrow so need to buy the cable and dig in, connections can come later.

Is there a spark out there who can calculate the size of armoured cable I should buy for a 75metre run, to support a 500watt halogen light on the end.

Cheers Tazzatime

[Plotloss]

1.5mm SWA

[tazzatime]

Plotloss

Thanks for that speedy response.

If I changed my mind and wanted to support 2 x 500w would that still be ok at 1.5 or should I go to 2.5 or above.

Cheers

Tazzatime

[Smiler.]

Is it fed via an RCD/RCBO? If not, you will need to check the Earth-loop impedance.

Is the cable terminating at a metallic enclosure? If not, would be worth using 3-core to provide Live/Neutral/Earth (I usually spec that anyway, just to be safe).

[Plotloss]

tazzatime said:

Plotloss

Thanks for that speedy response.

If I changed my mind and wanted to support 2 x 500w would that still be ok at 1.5 or should I go to 2.5 or above.

Cheers

Tazzatime

1kW is fine on 1.5

Above that up the gauge to 2.5

[tazzatime]

Smiler. said:

Is it fed via an RCD/RCBO? If not, you will need to check the Earth-loop impedance.

Is the cable terminating at a metallic enclosure? If not, would be worth using 3-core to provide Live/Neutral/Earth (I usually spec that anyway, just to be safe).

Hi Smiler

I intended to use 3-core, thanks for the advice on the RCD/RCBO, I have a pal who is a qualified electrician who I will get to do the installation. But cannot contact him at the moment and need to get the cable dug in before I will be able to talk to him.

Cheers

[Smiler.]

tazzatime said:

Smiler. said:

Is it fed via an RCD/RCBO? If not, you will need to check the Earth-loop impedance.

Is the cable terminating at a metallic enclosure? If not, would be worth using 3-core to provide Live/Neutral/Earth (I usually spec that anyway, just to be safe).

Hi Smiler

I intended to use 3-core, thanks for the advice on the RCD/RCBO, I have a pal who is a qualified electrician who I will get to do the installation. But cannot contact him at the moment and need to get the cable dug in before I will be able to talk to him.

Cheers

Are you intending to add this to an existing circuit, or add a new dedicated one?

As Plotters says, 1kw is fine on 1.5mm² SWA, but doesn't leave much over if it's an existing circuit. You can get 100W & 200W linear TH lamps, but at 75m, 500W might be needed.

[tazzatime]

Smiler. said:

tazzatime said:

Smiler. said:

Is it fed via an RCD/RCBO? If not, you will need to check the Earth-loop impedance.

Is the cable terminating at a metallic enclosure? If not, would be worth using 3-core to provide Live/Neutral/Earth (I usually spec that anyway, just to be safe).

Hi Smiler

I intended to use 3-core, thanks for the advice on the RCD/RCBO, I have a pal who is a qualified electrician who I will get to do the installation. But cannot contact him at the moment and need to get the cable dug in before I will be able to talk to him.

Cheers

Are you intending to add this to an existing circuit, or add a new dedicated one?

As Plotters says, 1kw is fine on 1.5mm² SWA, but doesn't leave much over if it's an existing circuit. You can get 100W & 200W linear TH lamps, but at 75m, 500W might be needed.

Was intending to add to an existing circuit.

[Smiler.]

tazzatime said:

Smiler. said:

tazzatime said:

Smiler. said:

Is it fed via an RCD/RCBO? If not, you will need to check the Earth-loop impedance.

Is the cable terminating at a metallic enclosure? If not, would be worth using 3-core to provide Live/Neutral/Earth (I usually spec that anyway, just to be safe).

Hi Smiler

I intended to use 3-core, thanks for the advice on the RCD/RCBO, I have a pal who is a qualified electrician who I will get to do the installation. But cannot contact him at the moment and need to get the cable dug in before I will be able to talk to him.

Cheers

Are you intending to add this to an existing circuit, or add a new dedicated one?

As Plotters says, 1kw is fine on 1.5mm² SWA, but doesn't leave much over if it's an existing circuit. You can get 100W & 200W linear TH lamps, but at 75m, 500W might be needed.

Was intending to add to an existing circuit.

Might be an idea to check the rating of the circuit breaker & what else is on the circuit.

[tazzatime]

Smiler. said:

Might be an idea to check the rating of the circuit breaker & what else is on the circuit.

Ok will do thanks

[Raverbaby]

75m is a fair distance and you will get volt drop, you'd be aswell putting 2.5mm in just to cover yourself.
Have a wee butchers at this guide, it suggests 2.5mm.


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

[Solitude]

oh, and the regs say you have to earth the sw too, so either terminate one end into an earthed metal enclosure, or "clamp and fly".
Make sure you dig 18" below, and you should run warning tape above too. !!!!!

[Grandad Gaz]

Solitude said:

Make sure you dig 18" below, and you should run warning tape above too. !!!!!

Is that really necessary with armour??

[tazzatime]

Guys

Thanks for all your help. I think I will go with 2.5mm, to be on the safe side in case I want to add a second Halogen later.

Cheers

Tazzatime

[Solitude]

Grandad Gaz said:

Solitude said:

Make sure you dig 18" below, and you should run warning tape above too. !!!!!

Is that really necessary with armour??

if you bury it....yes.
If it is exposed (surface clipped along a wall/fence, or lay down in shrubbs) then no.
But burying is 18".

[Ganglandboss]

Raverbaby said:

75m is a fair distance and you will get volt drop, you'd be aswell putting 2.5mm in just to cover yourself.
Have a wee butchers at this guide, it suggests 2.5mm.


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

The cable needs to be sized for the size of the breaker protecting it, not the load. A lighting circuit on a 6A breaker requires a cable size of 4mm according to that website (my copy of the wiring regs is at the office so I cannot check it properly right now).

Edited by Ganglandboss on Thursday 19th August 19:52

[Raverbaby]

Ganglandboss said:

Raverbaby said:

75m is a fair distance and you will get volt drop, you'd be aswell putting 2.5mm in just to cover yourself.
Have a wee butchers at this guide, it suggests 2.5mm.


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

The cable needs to be sized for the size of the breaker protecting it, not the load. A lighting circuit on a 6A breaker requires a cable size of 4mm according to that website (my copy of the wiring regs is at the office so I cannot check it properly right now).

Edited by Ganglandboss on Thursday 19th August 19:52

Maybe I'm misreading the website, but are you saying that a 4mm cable on a 75m run would need to be limited to a 6amps MCB? Surely not?

From the website:-
Required Cable Size 2.5 mm
Voltage Drop 5.22 Volts.
Percentage Drop 2.3%
Current Load 4.00 Amps
Max Cable Load* 24.9 Amps

My big red books in the van and I cant be arsed going out cos its been a long day

[Ganglandboss]

Raverbaby said:

Ganglandboss said:

Raverbaby said:

75m is a fair distance and you will get volt drop, you'd be aswell putting 2.5mm in just to cover yourself.
Have a wee butchers at this guide, it suggests 2.5mm.


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

The cable needs to be sized for the size of the breaker protecting it, not the load. A lighting circuit on a 6A breaker requires a cable size of 4mm according to that website (my copy of the wiring regs is at the office so I cannot check it properly right now).

Edited by Ganglandboss on Thursday 19th August 19:52

Maybe I'm misreading the website, but are you saying that a 4mm cable on a 75m run would need to be limited to a 6amps MCB? Surely not?

From the website:-
Required Cable Size 2.5 mm
Voltage Drop 5.22 Volts.
Percentage Drop 2.3%
Current Load 4.00 Amps
Max Cable Load* 24.9 Amps

My big red books in the van and I cant be arsed going out cos its been a long day

No. I'm saying the breaker should be rated at 6A as that is generally the smallest you can get (3A breakers are available but not that common, plus the OP said he may want to go for two luminaires which works out at 4.35A).

The cable sizing calcs have to be based on the highest potential load which the cable could carry (which is the same as the rating of the breaker) rather than the actual load.