Garage power

[John-SJW]

An issue with 60m of 2.5mm is voltage drop. In a district where voltage fluctuates, this may be an issue. In my place it is always 249-250 volt, so I am lucky, other may not be. So a 4mm cable may be the way to go, even though it appears oversized for the current it handles.

 

[pc1966]

This is when the OSG is your friend, a quick look at Table 7.1(i) has some quick answers to most initial guess of current & length combinations.

However, the OP said the client wants 32A option for the future so that really pushes for 4mm cable now. Also the difference between 2.5mm and 4mm 2-core SWA is around the 50p/m mark so for 30m or so run around £15 and compared to the labour, etc, involved it is hardly worth arguing over!

 

[Strima]

In my place it is always 249-250 volt

But we still use a nominal voltage of 230 at the design stage. Can you guarantee in ten years time that the voltages will be the same?

 

[Dustydazzler]

An issue with 60m of 2.5mm is voltage drop. In a district where voltage fluctuates, this may be an issue. In my place it is always 249-250 volt, so I am lucky, other may not be. So a 4mm cable may be the way to go, even though it appears oversized for the current it handles.

60m

i though the distance was 30m ?

 

[John-SJW]

But we still use a nominal voltage of 230 at the design stage. Can you guarantee in ten years time that the voltages will be the same?

Not at all. But as a transformer is not far from me it is a good bet it will remain that way in my case. But generally you are right.

I recall one Dutch guy who said the British oversize cables. He said, with widespread adoption of LED lights you are still installing 1.5mm lighting cable when 1.00mm is more than adequate. Lightly used rings are oversized with a total of 5mm. But the oversizing may compensate, even if ever so slightly, over voltage drop.
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60m

i though the distance was 30m ?

typo. approx 98 foot, a fair distance in a domestic house. Then wires off that.

 

[pc1966]

He said, with widespread adoption of LED lights you are still installing 1.5mm lighting cable when 1.00mm is more than adequate.

You do get 1mm for light circuits and it is often used.

The problem is the IET regs have 1.5mm as smallest for power circuits (not sure exactly why, might be for mechanical reasons, or a throwback to the days of 15A rewirable fuses being the next size up from 5A) so for many a stock of 1.5mm is more generally useful stuff to have for odd fused spur, etc, as well as for lights.

 

[John-SJW]

Also the difference between 2.5mm and 4mm 2-core SWA is around the 50p/m mark so for 30m or so run around £15 and compared to the labour, etc, involved it is hardly worth arguing over!

At TLC 2.5mm 3 core swa for 50m is £50.52. 4mm for 50m is £99.60. x2.

 

[Strima]

installing 1.5mm lighting cable when 1.00mm is more than adequate

Just poor design using 1.5mm when 1.0 would suffice in the vast majority of installations.

As an aside I use 1.0mm when installing new but a lot of installations in my area use 1.5mm so I use that when modifying or repairing.

 

[pc1966]

At TLC 2.5mm 3 core swa for 50m is £50.52. 4mm for 50m is £99.60. x2.

Do they need 3-core?
Why 50m, I thought the run was 30m?

 

[Spoon]

Do they need 3-core?

It might not be needed but personally I would use 3 core. It's only 25p more per meter, so an extra £7.50 for 30 meters, which isn't that bad.

 

[pc1966]

It might not be needed but personally I would use 3 core. It's only 25p more per meter, so an extra £7.50 for 30 meters, which isn't that bad.

Fair point, no harm in having the extra CPC in it.

 

[Dustydazzler]

I always use 3c

 

[John-SJW]

You do get 1mm for light circuits and it is often used.

I recently saw some new build houses by a developer and all lighting was still in 1.5mm, despite in-built kitchen lights and downlighters all being LED. Old habits....

The one off general builders (those who do it all themselves), will not budge from 1.5mm for lighting, not understanding it, so lean on the side of caution. These guys wire houses as rule of thumb. One 32A ring for upstairs, one for down and one for the heavy appliances in the kitchen with all having FCUs over the worktops. Radials for the ckr and immersion. 25mm meter tails no matter. It works, no calculations needed for them.

Many people around the world have slagged rings, looking at the British as odd for using them - they do have their advantages for sure. The great thing about them is that they are generally foolproof from an installation point, using only rule of thumb. I read that was one of the reasons they were promoted in 1942 when planning for the post war building boom, with millions of men being demobbed needing to pick up skills quickly. Hence why we have 13A fuses in plugs, and restrictions of 13A for spurs, to the bemusement of other nations.
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Do they need 3-core?
Why 50m, I thought the run was 30m?

Just an e.g, of price difference. Not using 3 core is well....

 

[davesparks]

I recall one Dutch guy who said the British oversize cables. He said, with widespread adoption of LED lights you are still installing 1.5mm lighting cable when 1.00mm is more than adequate. Lightly used rings are oversized with a total of 5mm. But the oversizing may compensate, even if ever so slightly, over voltage drop.

A Dutch guy said the British oversize cables, well that's great but what does that have to do with anything? Everyone is entitled to their opinion, that doesn't make their opinion any more valid than anyone else's.

The installation of LED lighting is largely irrelevant, the cable size is based on the nominal current for the circuit. The nominal current of standard lighting circuits hasn't changed.