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I recently set up a soldering station on my old desk in the corner of my room. However there are no power sockets near there so I had to daisy chain two extensions cords to deliver power to my solder station and fan. Is it a safe solution?

I read online that it is dangerous because you can overload the socket but I doubt that. I live in the UK and in every electrical appliance it is legally required to have a fuse, and just in case I made sure to check that every single appliance plugged in to the extension cords have a fuse. On every block of the power extension there is an additional fuse. I am also not exceeding the 13 amp limit of the plug, (double checked with a calculator). There is one more thing though, I am using the first power extension to power my desk (two monitors and pc) but that adding the current draw of that to my total current draw still does not exceed 13 amps. I live in the UK and the electrical system is pretty safe. A fuse for every plug, a fuse for every wall, safest plug in Europe (potentially the world) and an RCD that protects every socket in the house. Is it safe to do so?

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  • \$\begingroup\$ If you're running a 13A load, you should be using 12 guage extension cords(not all are designed to run a full 15A circuit, let alone continuously). As long as the cords are adequately sized for their length and electrical load you'll be fine. If they aren't, you could easily start a fire. \$\endgroup\$
    – K H
    Commented Mar 14, 2021 at 7:50
  • \$\begingroup\$ If it never gets too warm, it's safe. \$\endgroup\$
    – D.A.S.
    Commented Mar 14, 2021 at 7:55
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    \$\begingroup\$ @KH This is a UK post, so the rules are a bit different. They won't let you sell a cord too small. \$\endgroup\$
    – SomeoneSomewhereSupportsMonica
    Commented Mar 14, 2021 at 7:57
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    \$\begingroup\$ If your soldering station (or indeed the total load on the extension cable) is a few hundred watts or less, it won't be a problem. \$\endgroup\$
    – user16324
    Commented Mar 14, 2021 at 13:18
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    \$\begingroup\$ @Justme In my area of the UK we don't have fire inspectors but it's certainly good to know thanks! :D \$\endgroup\$
    – James Barnett
    Commented Mar 16, 2021 at 18:49

2 Answers 2

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Extension cords are more dangerous than direct connections. More extension cords plugged in series are yet more dangerous. However, life is dangerous, and we all accept some danger, in driving or cycling on the roads for instance. The regulations around extension leads and driving try to reduce that danger to some low level that we accept as reasonable.

The fuse used in UK plugs generally protects the wiring against overheating due to a short-circuit, if it's properly sized. Too often, we see a standard 13 A fuse used with undersized wiring. Note that a fuse will not generally protect against a low level of overload, a fuse will typically carry 200% of rated current for long enough for an under-sized cable to overheat.

However the fuse also provides one point of danger. Strained springs contacting the fuse could cause a high resistance, which could overheat and start a fire. Other points of potential high resistance are loose screws where the wires enter the terminals, and loose springs in the sockets connecting to the plug pins. This last one is exacerbated if the plugs are not fully in.

Adding one fused extension lead to a circuit adds another 8 (eight) series potentially loose connections to the circuit, many of which could start a fire. Every further extension lead connected adds another 8 connections.

Every extra extension lead added offers to opportunity to bury the cable underneath a carelessly tossed cushion or pile of clothing, or maybe route it tidily under a rug. This thermally insulates the cable, making it reach a far higher temperature than would be the case in free air, and providing fuel to burn should the cable catch fire.

Extension leads are also trip hazards.

Many extension leads confuse the route. If you want to quickly plug in a fan heater, which is the best socket to use?

In your case, a soldering iron and a couple of PCs comprises a load so far below the rated current that it's likely to be safe. Keep the cable route clear of walkways, and clear of clothes. Check all the plugs from time to time to make sure they are fully inserted.

If your situation changes, more people, piles of clothes, need for fan heaters, then re-assess the dangers.

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  • \$\begingroup\$ Does the UK not have rules about maximum distance between outlets and maximum width of wall space with no outlet? \$\endgroup\$
    – user80875
    Commented Mar 14, 2021 at 11:41
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    \$\begingroup\$ @CharlesCowie We may do now. We also have 800 year old buildings retrofitted with electricity in the 1930s. And all sorts in between. \$\endgroup\$
    – user16324
    Commented Mar 14, 2021 at 13:20
  • \$\begingroup\$ @CharlesCowie IIRC you can serve 1000 ft^2 with as many sockets as you like from one 30 A fused ring main. \$\endgroup\$
    – Neil_UK
    Commented Mar 14, 2021 at 14:10
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    \$\begingroup\$ @CharlesCowie Brain Dummond is right, most houses or buildings are very old and the electrical system is old (still safe). In fact my house has no ethernet, requiring me to use an ethernet frequency wall adapter just to access the internet from my desk without using wifi, and it's slow because of the old electrical system. \$\endgroup\$
    – James Barnett
    Commented Mar 16, 2021 at 18:56
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There are two main risks with daisy chaining extension leads.

The first is that it's easy to overload the leads. The 13A fuse in a British plug is "slow blow". It will happily accept surges of many tens of amps as an appliance starts up. But the down-side is that it will take a long time to blow, even at overloads up to 20A. At that point, it actually becomes a liability, as the fuse tends to get hotter than everything else, and melts the plug.

The second risk is the total resistance of the Earth wires gets higher as the total length of the extensions gets longer. You end up in a situation where even a dead short at the end takes a considerable time to blow the 13A fuse. This could lead to someone being electrocuted if there's a major fault.

But if your leads aren't too long, and you are confident that the load will never exceed 13A, you should be OK.

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  • \$\begingroup\$ Yes it should be fine. But as I said in my post, not only is there a fuse in the socket of the wall. But there are actually fuses rated for 10 amps in each socket of the extension, meaning that in the event that anything goes above 10 amps then some fuse somewhere along the connection will go off. The only time I can see the 13 amp limit being exceeded is during the period of inrush current, however I am fairly certain that my appliances have soft-starting protection circuits. \$\endgroup\$
    – James Barnett
    Commented Mar 16, 2021 at 18:53
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    \$\begingroup\$ Isn't the resistance of the earth wires less of an issue re long runs increasing electrocution risk, if the installation is RCD protected? \$\endgroup\$
    – saxbophone
    Commented Nov 24, 2022 at 14:17
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    \$\begingroup\$ @saxbophone Yes it is a lot safer if there is an RCD. \$\endgroup\$
    – Simon B
    Commented Nov 24, 2022 at 22:07

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