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Which thickness of extension lead for usual desktop computer set?

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Fernando Negro
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Which thickness of extension lead for usual desktop computer set?

#1 Post by Fernando Negro »

I've finally bought a 2.1 speaker system for my (GNU/Linux-supported) hi-fi sound card - which means that, I'll have to use a 4 sockets electrical extension lead, instead of my current 3 sockets one.

That is, I need a 4 sockets extension lead, where I will plug in the power cables of my:

- desktop computer
- 19'' monitor
- 2.1 speaker system
- small lamp

So, looking for one, I found two (1.5 meters in length) that interest me, where the only difference between the two, is what I've discovered to be their "cross-sectional area" (https://www.quora.com/What-do-we-mean-b ... -a-circuit) - where, one is listed as having 1.5mm² and another one 2.5mm². (The full description of each cable type is "H05VV-F3G1.5mm²" and "H05VV-F3G2.5mm²".)

1) https://www.castroelectronica.pt/produc ... velleman-2

2) https://www.castroelectronica.pt/produc ... --velleman

They're both listed, at the online shop in question, as being able to handle "3500 W" of power (which is more than enough for my needs). But, I suspect that this may be an error on one of the lists - since that, if the cables' thickness is different, the number of watts that each cable is capable of dealing with should be different also... Or is my assumption wrong?

Anyway, the reason why I think this is a question of interest also for other people on this forum, is because,

Almost every desktop computer home user should come across the same type of purchase decision (whether s/he notices the difference in the cables or not) that I'm about to make. So, when the time for such a purchase comes for everyone,

What amount of "thickness" of an extension lead is the one recommended for the usual desktop computer set?

(Should we worry about this aspect, or only about the number of watts that the extension leads are listed as being able to handle?)

My concern, is one about SAFETY. Since that,

1) I know that, if a cable is too thin for the amount of current that it will handle, it can overheat and cause a fire, and

2) if a cable is too thick, my fear is that, because of it being able to carry more current, that such can increase the amount of damage on a computer, in case of a power surge.
I just *love* the stability, much more bug-free nature, and modular installation options of Debian. Apart from the unfortunate adoption of "systemd" (viewtopic.php?f=20&t=129881&start=165#p671030) this distribution is *great*.

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Re: Which thickness of extension lead for usual desktop computer set?

#2 Post by ticojohn »

As both those extensions claim the same power handling capability yet have different wire sizes, I would contact the vendor to clarify the discrepancy, and maybe even ask for their recommendation. In my opinion, the extension with the 2.5mm wires (equal to 10 gauge wire) would probably be overkill.

That being said, the extension with the 1.5mm wires should be capable of handling about 1400 watts. My home desktop compute has a 450 watt power supply, I have a 19" LCD monitor, powered speakers (25 watts) and a HP deskjet printer/scanner. All of that is plugged into a 900 watt UPS that gives me 5 minutes of backup power.
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Re: Which thickness of extension lead for usual desktop computer set?

#3 Post by FreewheelinFrank »

Yes, a thicker cable can handle more power. It's more usual to think about current for a cable as mains voltage is fixed. A thicker cable can handle more Amps.

Appliances are usually rated in Watts for power. Current may vary with local voltage. Ball park ratings for your appliances are:

Desktop computer : 60-250W.
Monitor: 20-100W.
Speakers: 20-50W.
Lamp: 10W.

Total Watts = 410W tops.

I don't know what the voltage is in your country, but in the UK it is a nominal 240V.

So that would be a current of 1.7 Amps max. (W = V x A).

Your "thin" cable is rated at 16A max and your "thick" cable at 20A max.

So both can handle your four appliances. Even the "thin" cable is not going to overheat with that load. You would probably have to connect ten of each to overload it.

Both cables can carry enough current to cause problems in the event of a short circuit - which is why, at least in my country, plugs have a fuse. Your probably want a 3A fuse in your plug, and if you have ever seen a 3A fuse wire, it is thinner than even one strand of the mains cable wire, much thinner.

Even a hair-thin 3A fuse wire cannot protect electrical equipment from a power surge - you need a special surge protection device to do that.

In short, the thinner cable is the one you want; the thicker cable is for things like electrical fires, freezers, electric ovens, welding machines, compressors etc etc that draw a lot of power.

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Re: Which thickness of extension lead for usual desktop computer set?

#4 Post by ticojohn »

You got it @FreewheelinFrank . The only thing I might add is that if the OP is using the machine for gaming and has some high powered graphics card, then he might need another 100 watts. But even so the lighter duty extension would probably handle the load. And by the way, I believe the OP is in Portugal (probably 240V/50hz). Oh, and I think the OP's issue is that both products he listed say they are rated at 3500 watts even though one has a much smaller wire diameter (1.5mm vs 2.5mm for the other). That was why I suggested he contact the vendor for clarification.
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Re: Which thickness of extension lead for usual desktop computer set?

#5 Post by Fernando Negro »

ticojohn,

I did contact the vendor, about the discrepancy in power handling capability, while also asking for a recommendation - but, the first answer I got was from an ignorant sales manager, only telling me to choose between which "size" I "like" most (which I interpret as being a reference to the length of the cable - even though I mentioned the word "thickness" twice, on my first message).

(After receiving such an answer, I elaborated with some extension on what I was talking about, and asked him to forward such message, together with my first one, to someone in the department specifically responsible for electrical extension leads - but, given the quality of the first answer I got, I don't know if I'm going to receive another and satisfying one.)

Anyway, because I thought that this might be somewhat of an important issue, to others who - like me - were not aware of this aspect, I thought it would be also of interest to other people to talk about this, in here.

Thank you, for your explanation.


FreewheelinFrank,

Here, in Portugal (i.e. the European Union), the voltage is 220 volts.

Yes, that's what I suspected already - that the thinner one was enough for my needs...

Since that, if "too thin" electrical extension leads, sold at stores, were a problem with computers, we should have read lots of stories already, of people who had problems because of not being careful about this aspect. And, knowing that there are electrical machines (like the ones you mentioned) that draw much more power, I suspected the "thicker" extension lead to be made thinking of those.

Thank you very much, for your most elucidating explanation. :)
I just *love* the stability, much more bug-free nature, and modular installation options of Debian. Apart from the unfortunate adoption of "systemd" (viewtopic.php?f=20&t=129881&start=165#p671030) this distribution is *great*.

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Re: Which thickness of extension lead for usual desktop computer set?

#6 Post by FreewheelinFrank »

@ticojohn
Another 100w would only add about 0.42 Amp, bringing the total to 2.12 Amp, well within the cable's 16A rating at 300V, so the cable would definitely handle that.

@Fernando Negro
It is probably the plug or extension that is the limiting factor, as even the thinner cable can handle 16A at 300V = 4800 W.

The plug for the extension seems to be a type F which are rated at 16A. At 220V max power would be 3520W, so you can't draw more power without exceeding the rating of the plug.

You might ask what the point of the thicker cable is if the plug is the limiting factor....

Well the resistance of the thicker cable is lower (0.66 Ω vs 1.2 Ω per 100m), so warming/power loss would be less with an appliance which draws a high current.

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Re: Which thickness of extension lead for usual desktop computer set?

#7 Post by Fernando Negro »

Another most elucidating explanation. :)

Thank you very much for that as well, FreewheelinFrank.
I just *love* the stability, much more bug-free nature, and modular installation options of Debian. Apart from the unfortunate adoption of "systemd" (viewtopic.php?f=20&t=129881&start=165#p671030) this distribution is *great*.

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Re: Which thickness of extension lead for usual desktop computer set?

#8 Post by ticojohn »

@FreewheelinFrank , I just want to, once again, point out that there is a discrepancy in the specifications of the two devices. Both are supposedly rated at 16 amps. One of the extensions has 2.5 mm wires, which is approximately 10 AWG wire, and it could probably handle 16 amps. However, the other extension has 1.5 mm wires, which is approximately 15 AWG, and is rated for about 5 amps. There is a huge difference. The smaller diameter wire might be able to handle 1000 watts, or thereabout. Without KNOWING the OP's equipment and power requirements it is too offhanded to just conclude that the cheaper (ie smaller wires) unit will be adequate, although it would probably be okay. But for 3 euros more for the heavier duty item why not just go that way. Just my opinion.

UPDATE: Okay, after more research I find that a stranded Cu wire of 1.5 mm cross section can handle up to 13 amps (assuming A/C). At 50Hz, instead of US standard 60Hz, the capacity is slightly lower, but not significantly so. Wouldn't want to do 13 amps continuously however. So, that extension with 1.5 mm wire should be fine. Thanks for keeping me honest @FreewheelinFrank .
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Re: Which thickness of extension lead for usual desktop computer set?

#9 Post by FreewheelinFrank »

H05VV-F 3G1.5 - 3 x 1.5 mm² is rated at 16A, H05VV-F 3G2.5 - 3 x 2.5 mm² at 20A, but both extensions use a 16A plug, so that is obviously the limiting factor. 20A would exceed the rating of the plug and the domestic power circuit as well probably.

https://procab.be/be-en/products/d/pc3g ... 2---16-awg

https://procab.be/be-en/products/d/pc3g ... 2---13-awg

The best thing to do would be to check the actual power requirements for the equipment of course, but as I have taken the upper limit of power ranges quoted on the internet, and the rating of the extension socket still exceeds total power requirement by a factor of almost 10, I'd be quite relaxed about connecting those four devices on the thinner cable.

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Re: Which thickness of extension lead for usual desktop computer set?

#10 Post by ticojohn »

FreewheelinFrank wrote: 2021-09-21 07:12 The best thing to do would be to check the actual power requirements for the equipment of course, but as I have taken the upper limit of power ranges quoted on the internet, and the rating of the extension socket still exceeds total power requirement by a factor of almost 10, I'd be quite relaxed about connecting those four devices on the thinner cable.
After further review, I agree. My initial concern with the thinner wire was based on a wire chart that indicated that a 1.5mm wire was good for only about 5-6 amps, and depending on the OP's equipment that my have been a bit of a strain. However, going back to the chart I found that the 5 amp rating was for a solid conductor. A stranded conductor can handle significantly more A/C current than a solid conductor (multiple strands have higher surface area). So, I concur with your assessment.
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Re: Which thickness of extension lead for usual desktop computer set?

#11 Post by sunrat »

For the tiny price difference, go for the higher rated one. You might want to plug a heater or coffee pot into it one day!
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Re: Which thickness of extension lead for usual desktop computer set?

#12 Post by ticojohn »

sunrat wrote: 2021-09-21 15:27 For the tiny price difference, go for the higher rated one. You might want to plug a heater or coffee pot into it one day!
Right on! I kind of suggested earlier that since the price difference wasn't that much that going with the heftier version makes sense. I usually buy extensions that are heavier (current wise) than probably necessary. Better to over engineer something than to under engineer it.
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Re: Which thickness of extension lead for usual desktop computer set?

#13 Post by Fernando Negro »

FreewheelinFrank,

I'm finally using the 1.5mm² extension lead I ordered.

And, the specs are the ones that can be seen on the following product's webpage - that exists on the manufacturer's website.

http://en.aigostar.com/specification_De ... x?id=12959

(It says also on the label that came with it: "16A 250V, MAX 3680W". So, the corresponding list at the online shop I used is wrong, and only correct about the cable type - including "thickness" - in question...)

The following, is the product's webpage with pictures, where one can see the warning "MAX:3680W" engraved on the extension lead itself.

http://en.aigostar.com/Total_Details.aspx?id=12959

So, your calculations were right. :)

The power limit for this 1.5mm² type of extension lead, is indeed several times the maximum power used by a regular desktop computer user.

I've even made the test of holding the extension cable itself, after hours of use, and I feel no warmth whatsoever.


Everyone else,

My current PC is not the only computer I wanted to buy an extension lead for... So, the more items a person possibly buys, the more noticeable the price difference becomes.

And, although for a Western buyer (of a single cable) the mentioned price difference is not significant, for someone in a poor country - where €2.50 can indeed make a difference - I think that, what was discussed on this thread is always information of interest.
I just *love* the stability, much more bug-free nature, and modular installation options of Debian. Apart from the unfortunate adoption of "systemd" (viewtopic.php?f=20&t=129881&start=165#p671030) this distribution is *great*.

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