I installed 1mm2 copper AC power cable across house for video surveillance (8 cameras, Power Consumption for each camera is Max 4W, 12V). For each camera has its own 220V->12V converter rated 3A. Total ac power cable length is about 150 meters. (In case that cameras are connected to APC Smart-UPS, I plan to plug 50" LED TV (190W) to that AC line too)

I am reading AWG specs in Wikipedia. I also read AWG Sizes and Current Limits table. Then I looked on my computer power cord. enter image description here

So, 17 AWG area is 1mm2, AWG Sizes and Current Limits shows that max current is 2.9 amps. But my computer power cable is labeled that it is 0.75mm2 and max amperage is 16 amps.

So, questions:

  1. How can it be, that a cable which is less than 1mm2 can handle larger load than 17 AWG?
  2. Or my computer cable has different measurement system used? Or listed 16A mean peak only?
  3. And how can I actually calculate max cable load by cable area (mm2)?
  4. Or AWG Sizes and Current Limits table is wrong?
  5. General question - Will the installed 1mm2 cable be good enough for that load?
  • 3
    \$\begingroup\$ 16A/250V is plug rating, not wire rating. \$\endgroup\$
    – Kamil
    Jun 13, 2014 at 19:42
  • \$\begingroup\$ Then looks like cable can about 2 amps... \$\endgroup\$
    – Guntis
    Jun 13, 2014 at 19:44

2 Answers 2


How can be, that cable witch is less than 1mm2 can handle larger load than 17 AWG?

Or my computer cable has different measurement system used? Or listed 16A mean peak only?

It can't be.

16A/250V on your photo is just plug rating, not whole wire rating. Check other end of wire - it may have 10 or 20A rating :)

And how i can actually calculate max cable load by cable area (mm2)?

You can use some table. Table you mentioned (AWG Sizes and Current Limits) has a note:

Current (Ampacity)

The current ratings shown in the table are for power transmission and have been determined using the rule of 1 amp per 700 circular mils, which is a very conservative rating.
For reference, the National Electrical Code (NEC) notes the following ampacity for copper wire at 30 Celsius:
14 AWG - maximum of 20 Amps in free air, maximum of 15 Amps as part of a 3 conductor cable;
12 AWG - maximum of 25 Amps in free air, maximum of 20 Amps as part of a 3 conductor cable;
10 AWG - maximum of 40 Amps in free air, maximum of 30 Amps as part of a 3 conductor cable.


Or AWG Sizes and Current Limits table is wrong?

These are many tables, maximum currents are calculated with diffrent rules. There are NEC standards, IEC standards, cable manufacturers standards, some local rules in many countries in the world. I think IEC is not bad idea for reference, but you can use any other reliable organisation or company.

Here is wire calculator based on "IEC 60364-5-52: Low Voltage Electrical Installations (2009)" standards (low voltage is < 1kV in IEC nomenclature).

General question - does installed 1mm2 cable will be good enough for that load ?

For 8 camera power supplies (probably not more than 50W total) and 190W TV - this is more than enough. These camera power supplies have 3A/220V rating, but 3A is peak current.

Additional note:

If you have a lot voltage converters connected to one UPS - turning them on all at once may cause very high pulse current and your UPS may have problems with startup.

Maybe it doesn't matter for 8 small camera power supplies and 1 big TV, but you should know.

3A on your camera power supply is pulse current for charging converter input capacitor.


A couple things about this installation.

First, when wiring mains power, you must follow the rules of your jurisdiction regarding wiring methods and types of cables used. These are very well established.

The photos you have shown are of a type of cable we call cordage. This is for appliance cords. It is not the same as cabling used in-wall, which has different insulation and sheathing characteristics. You must use appropriate types. You are typically not allowed to attach cordage to walls as a substitute for proper wiring, at mains voltages.

You are examining the rating of the wires based on what you feel are normal loads. If the electrical system was designed for normal conditions, there would be no need for fuses, circuit breakers, ground wires or even RCDs! You need to design for failure conditions. That means running ground wires, and that means your 1.0mm cabling must be protected by a fuse/breaker appropriate for 1.00mm wire, such as whatever your jurisdiction requires, e.g. a 6A fuse.

If you find those rules inconvenient, and don't want to follow them, then you have a possible workaround: the rules are relaxed for low-voltage low-current wiring. Rather than distribute 230V all over the house to individual 230V-12V wall-warts, you could eliminate the wall-warts and distribute 12V DC. Then your wiring would be carrying only 12V, and would have fewer regulatory issues to deal with. Depending on your jurisdiction of course.

  • \$\begingroup\$ The trouble with switching from 230V to 12V is that the currents increase roughly twenty-fold. Which makes the problem of cable sizes much worse than before. \$\endgroup\$
    – Simon B
    Mar 5, 2020 at 9:42
  • \$\begingroup\$ @SimonB it's either a problem or it isn't. Have you crunched the numbers? \$\endgroup\$ Mar 5, 2020 at 10:57
  • \$\begingroup\$ Of course it's a problem. Take your example of a cord fused at 6A for 230V. That will do for any appliance up to 1kw (it works out at 1380W). If you connect a 1kW appliance at 12V, that's 83A. The 1mm cable will be a molten blob at that current. \$\endgroup\$
    – Simon B
    Mar 5, 2020 at 11:59
  • \$\begingroup\$ @SimonB this is a Q&A site. It is the very nature of answers that they exist in the context of questions. There are no blanket statements on StackExchange. OP has 4-watt cameras. Obviously if we were supporting a 1kw load, we would be having a different conversation about rewiring with mains-approved wiring methods. \$\endgroup\$ Mar 5, 2020 at 16:40

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