extend power cable - Optoma screen

[lenovo]

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]

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.

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]

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.

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]

what do you mean by Additional protection

I mean a fuse!

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, using under 0.75mm2 is '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.

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.

I'm trying to say it's not just the normal load to consider, it's what happens when there's a fault!

 

[lenovo]

@Avo Mk8 great, thanks.
Maybe thats the reason why UK cords contains fuse?

I was thinking about 3m extension.

So does it mean that 0.75mm2 cable will sustain 150W? In that case maybe 0.5mm2 cables are not meant to be used with 230V?

In case I use fuse (question would be for how many A, inside the male plug) -> 3m of 0.5mm2 cable -> screen, that should be fine? Just asking in theory...

Thanks

 

[Avo Mk8]

@Avo Mk8 great, thanks.
Maybe thats the reason why UK cords contains fuse?

It's certainly an advantage. Possibly related to the use of "ring final" circuits which came about because of a shortage of copper, and the desire to use the smallest size of cable practicable.

I was thinking about 3m extension.

A sensible length

So does it mean that 0.75mm2 cable will sustain 150W? In that case maybe 0.5mm2 cables are not meant to be used with 230V?

A thicker conductor means less resistance in the cable, and less power dissipated in it, so 0.75mm would not get as hot. I imagine the standards experts decided this would be the sensible minimum, given European fusing arrangements.

In case I use fuse (question would be for how many A, inside the male plug) -> 3m of 0.5mm2 cable -> screen, that should be fine? Just asking in theory...

Well, you would choose the fuse to match the current capability of the cable, so 3A.

Surely it would be easier and safer to use a piece of 0.75mm2 cable than muck about fitting a fuse into a Schuko plug making some sort of DIY bodge. Why not just do what the established safety standards suggest?

 

[lenovo]

@Avo Mk8
they told me there is a fuse 6.3A inside the screen.

So it means the only risk is that there is a shortage of the cooper or issue inside the screen?

yes, seems like u advised 0.75mm should be a way ... instead of hacking here something ... for a safety.

 

[Avo Mk8]

@Avo Mk8
they told me there is a fuse 6.3A inside the screen.

That's great. That's also the rating of the 0.75mm cable, so the two match. All good!

So it means the only risk is that there is a shortage of the cooper or issue inside the screen?

Which is unlikely. The fuse in the unit makes the whole thing as safe as practicable.

yes, seems like u advised 0.75mm should be a way ... instead of hacking here something ... for a safety.

I think you would be doing the right thing. Many thanks.

 

[lenovo]

@Avo Mk8 just to get better understanding ...
i checked my philips sonicare charger and it comes with 230V 0.5mm2... i believe fuse is not in the plug .. even not in the charger...
so thats strange, isnt it?

 

[Avo Mk8]

@Avo Mk8 just to get better understanding ...
i checked my philips sonicare charger and it comes with 230V 0.5mm2... i believe fuse is not in the plug .. even not in the charger...
so thats strange, isnt it?

I no longer have access to the standards on this, so I'm afraid can't look up the detail, but I think some chargers have such low power consumption (eg <5W) that risk of overload is considered unlikely and some safety considerations (eg flammability) become eased.
All of these products have to (well, are supposed to!) go through a design verification process to check they comply with applicable product standards. Different product categories have different requirements, and I'm sure you'll find exclusions or differences between different types or makes of product.
I'm also sure you will be able to find examples of products with 0.5mm flex. In fact I think it's allowed to be used for light fittings.
But your original query was over the use of 0.5mm extension cable for equipment that was fitted with 0.75mm flex, and as it turned out was also fitted with a 6A fuse, so I was just exploring why the smaller gauge of wire might not be the best thing to use.