Hardware Insights Forum

You may have heard of counterfeit extension cords. I haven't seen one of those in person, but I have seen counterfeit IEC320 cords.

One variety is branded "DHT Tech". Measuring the resistance on two of them gave these results:

Cord 1
All three lines: 1.2Ω

Cord 2
Live and neutral: 0.5Ω
Earth: 2.0Ω

In comparison, a real 1.0mm² power cord gave <0.1Ω on all lines.

At least they didn't mix up the wires. But the resistance measurements are worrying. If you run 10A through counterfeit cord 1, you get 240W dissipated in the cord. Not something you'd want to do - unless you like starting fires.

They get away with it because PCs don't draw that much power. At 2A you would get only 9.6W dissipated in counterfeit cord 1. The presence of counterfeits may be why they often warn against actions that aren't dangerous if done properly, like running a heater through an extension cord.

Another brand of dangerous power cables is Fan-Jet. I've also seen a few unbranded ones.

If you discover another type of counterfeit power cable, post it here.

Ouch! I haven't seen this myself, but they'd have to be using dangerously thin wires (>22AWG/0.64mm²) to get that kind of resistance.

22AWG is 0.326mm². The smallest wires allowed for mains cables here are 0.5mm² (approximately 20AWG), which is rare, and even that would be far, far less resistive than the Dangerously, Horribly Thin things I have here. 0.75mm² is probably the most common size. Seriously, what are they doing to get this resistance???

The difference is actually even larger because the cable I compared against is longer than the DHT things.

Ah, yes, I was thinking of the diameter, but yes, even 20AWG wires shouldn't have that sort of resistance.

Wait a minute - some of my non-counterfeit cords read even higher values on the meter. But I suppose that's due to oxidation of the contacts. I put the meter across the live side of a lamp (with the switch on) and got an extremely high resistance, but it worked fine when I re-inserted the bulb and plugged it in.

I cut the ends off the DHT cords and the first one mentioned still measured the same ultra-high resistance, and the cross-section was shockingly small (equivalent to, what, two strands of a proper cable???). I eventually hooked that cord across the +12V output of a PC PSU. There was smoke, but no fire.

The second DHT cord has wrong colours - black for live, blue for neutral and black/yellow for earth (the proper colours are brown for live, blue for neutral and green/yellow for earth).

Out of curiosity, how long was the cable you tried on the PSU? and what PSU was it?

The DHT cords were about 1.2m long and the cord I compared against about 1.7m.

I hooked it to 2 PSUs. An Antec Basiq and a Delta "Giant Power" (with no fan controller), don't remember the exact models. I originally tried to burn live using the former. When I tried to burn out both live and neutral in the DHT cord, the PSU shut down and for a while I couldn't get it to restart.

I then used the Giant Power to burn out the earth wire in the DHT cord. The cord I "burned out" is, of course, now a charred mess. The PSU wires didn't overheat.

I plugged the PSUs in using a chain of 3 cords.

Those Basiqs only go up to about 500W IIRC. That's terrible if you can melt a 1.2m power cable with a only a 500 Watt PSU without tripping the OCP

The Basiq is a 350W and the Delta is a 300W. Make of that what you will.

I just had to try running a heater through a chain of IEC320 cords, so I did so. The heater is rated at 1.5kW. There are five cords (besides the heater's own) in the chain. None of them are hot enough that I would be bothered (the warmest part is one of the plug/socket junctions). They are a mixture of 1.0mm² and 0.75mm². Aside from me replacing an IEC320 C13 on one cord with an extension-cord socket, the cords are unmodified.

But of course, they can't risk it and put IEC320 C14 inlets on heaters, as the next person who plugs one in with a counterfeit cord, which catches fire and burns the house down, would try to sue the heater manufacturer. (Which could technically be done even without knowing how to wire plugs and sockets, as there are ready-made IEC320-to-extension-socket adapters.)

LongRunner wrote:The Basiq is a 350W and the Delta is a 300W. Make of that what you will.

Even worse!