Question about T&E and spotlights

[thedanburgess]

Hi,

So I've just started to install some spotlights in a room in my house, and I always thought to use 1.5mm T&E so I've wired them all up and I've come to connect the main line in and noticed that it is 1.0 T&E. Am I okay to link the main line to my daisy chained spots on 1.5.


Some more information, the main line comes into the light switch and then out of the light switch to the next room, and then 1.0mm T&E to the existing light. As far as I can tell this is a radial circuit, the house was built last year if that helps.

Here's my poor attempt at a diagram.

 

[Sureitsoff?]

Yes

 

[thedanburgess]

Yes

Am I right in saying its okay, as the 1.0mm incoming cable will only carry x amount and 1.5 can carry more so wont be overloaded and wont cause a fire?
I presume I wouldn't be able to do it if it was the other way around. 1.5 coming in and then daisy chain on 1.0

 

[Taylortwocities]

The bit of essential information is what protective device (fuse/MCB) is on the lighting circuit.
Assuming that it is suitable for the 1.5mm² or the original 1.0mm² cable then you are ok.

PS. Most circuits in your house will be radial ("daisychain") circuits. The exception might be some of the socket circuits, these can be provided as ring final circuits.

 

[thedanburgess]

The bit of essential information is what protective device (fuse/MCB) is on the lighting circuit.
Assuming that it is suitable for the 1.5mm² or the original 1.0mm² cable then you are ok.

PS. Most circuits in your house will be radial ("daisychain") circuits. The exception might be some of the socket circuits, these can be provided as ring final circuits.

So it connects back to the MCB on a B6 and is also on the RCD

 

[flameport]

The 6A MCB will disconnect long before the current is high enough to damage the cable.
1.0mm T&E is good for at least 10A, and in many cases up to 16A.

1.5mm is rated for even more, and is never required in any domestic lighting installation.

 

[thedanburgess]

The 6A MCB will disconnect long before the current is high enough to damage the cable.
1.0mm T&E is good for at least 10A, and in many cases up to 16A.

1.5mm is rated for even more, and is never required in any domestic lighting installation.

The reason I ask if I can do the above is because I have plently of 1.5 T&E and no 1.0. Just trying to save a some money, obviously if its not advisable or shouldn't do it I will go and buy the 1.0

 

[flameport]

Use it if you want.
It will just be more difficult to terminate into the lights.

 

[EFLImpudence]

Did you not find it difficult - or at least awkward - to connect two 1.5mm² T&Es to the lights?

Flexible cable would have been much more suitable and 1mm² more than adequate.

 

[thedanburgess]

Did you not find it difficult - or at least awkward - to connect two 1.5mm² T&Es to the lights?

Flexible cable would have been much more suitable and 1mm² more than adequate.

It wasn't too bad the connectors are very sturdy

 

[winston1]

Why do so many people use oversized 1.5mm2 cable for lights?

 

[thedanburgess]

Why do so many people use oversized 1.5mm2 cable for lights?

After doing some more research it seems that 1.5 was common years ago when there was a couple of 500W halogen floodlights tagged on the circuit somewhere for outside lights.
So I've learnt today that 1.0mm is sufficient.

 

[JohnW2]

Why do so many people use oversized 1.5mm2 cable for lights?

Good question. Is it perhaps because it was (I think) fairly standard to use 3/0.029" cable for lighting circuits, and with that having a CSA of about 1.29 mm², the nearest metric size to that was 1.5 mm² ?

 

[flameport]

3/.029 was used for lighting circuits.
However so was 1/.044, which is 0.97mm²
Why there should be any preference for larger and more costly conductors is still unexplained.

 

[JohnW2]

3/.029 was used for lighting circuits. However so was 1/.044, which is 0.97mm²

That's true but, as I implied, I thought (maybe wrongly?) that 3/0.029" was much more common (which might 'explain', even if not justify, why 1.5mm² came so popular/fashionable). Was that not the case?

Why there should be any preference for larger and more costly conductors is still unexplained.

I agree. Even if historical practices such as I have suggested are the 'explanation' that wouldn't justify the widespread adoption of 1.5mm² (or, come to that, 3/0.029") by people capable of thought. So maybe some were incapable of thought, and the rest didn't even bother to think, but merely 'followed like sheep'?

Kind Regards, John