extend power cable - Optoma screen

lenovo · 2024-10-22T12:31:52+0100

Hello,
I have optoma screen de-9120ega | Optoma United Kingdom - https://www.optomaeurope.com/product/de-9120ega
which has 3g 0.75mm cable. I want to use extension ... so I was thinking, is there any reason for such a device use 0.75mm cable? I assume few electronics and small motor is inside.

Can I buy a extension with 3g 0.5mm?

Thanks!

Avo Mk8 · 2024-10-22T20:14:29+0100

lenovo said:
Hello,
I have optoma screen de-9120ega | Optoma United Kingdom - https://www.optomaeurope.com/product/de-9120ega
which has 3g 0.75mm cable. I want to use extension ... so I was thinking, is there any reason for such a device use 0.75mm cable? I assume few electronics and small motor is inside.

An electrical safety principle is that the fuse at the beginning of a circuit (to include the flex on a connected appliance), is there, at least in part, to protect the conductors, prevent fire etc. Presumably in your case the protective fuse/circuit breaker is in your distribution board, and is 16A.
0.75mm2 flex is rated around 6A, but is sturdy enough to withstand fault currents very much higher.
Further reducing the csa of flex increases the risk of heat/damage in the event of a fault.

I believe 0.75mm conductors are used because that is the minimum size for mains flex permitted by the regulations.

lenovo said:
Can I buy a extension with 3g 0.5mm?

The optoma manual states power consumption is 90 watts, thus current will be about 0.4A, so your suggestion of a 0.5mm cable would be OK from that point of view.
But the manufacturers of the screen fitted 0.75 because otherwise their product would not comply with the safety standards. If you don't add additional protection for a thinner cable, I would recommend you use the "correct size" 0.75mm2 for your extension lead!

lenovo · 2024-10-22T20:45:03+0100

hello, @Avo Mk8 appreciate your response!
they emailed me ie manufacturer:
All our products are manufactured in compliance with the safety and performance standards outlined in IEC / EN 62368-1 regulations.

We do not recommend using a different power cable for safety reasons. However, if you wish to do so then please make sure the cable complies with the IEC / EN 62368-1 safety regulations.

Avo Mk8 said:
If you don't add additional protection for a thinner cable, I would recommend you use the "correct size" 0.75mm2 for your extension lead!

what do you mean by Additional protection?
Is there really possibility of some failure and problem? Is is possible to use for 230V 0.5mm2?

I was expecting that size of the cable ie 0.5 or 0.75 ... is mainly based on the Power consumption / A of the end point device.

thanks!

Avo Mk8 · 2024-10-22T21:21:14+0100

lenovo said:
what do you mean by Additional protection

I mean a fuse!

lenovo said:
Is there really possibility of some failure and problem? Is is possible to use for 230V 0.5mm2?

It is possible yes, but as per the reaction of the manufacturer, not 'advised'.

The problem scenario is a fault developing that causes a current just lower than the breaker will trip, say 15A, and your thinner cable (rated at 3A) sits there, lets say coiled up by accident, getting hot, so there could be consequences.
If I've got my sums correct, and this is an extreme example, if you made a 10m long extension lead of 0.5mm flex, and the load sustained a fault current of 15A, then 150W could be dissipated in the cable, so a coiled up section might get hot enough to cause a fire.
I know this is contrived, but this is the sort of scenario a risk assessment considers, and why minimum cable sizes appear in the standards and regulations.

if your Optoma screen has a fuse in it, then I guess the chances of the 0.5mm cable being subject to such a load is minuscule, so do what you consider safe.