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Can I Use My Computer On An Extension Cord?

Discussion in 'Hardware' started by superstar, Jul 1, 2012.

  1. superstar

    superstar Command Sergeant Major

    I have one of those basic white extension cords lying around. It's rated at a max of 1650watts. My computer has a 460 watt power supply. Do you think it would be safe to use it on the extension cord? There's no ground wire in any of my house walls because the home was built in the 1920's, although the interior looks modern, and does have the third ground prong on the outlets. So plugging it into the extension cord with an adapter would pretty much be the same as plugging it into the wall.


  2. TimW

    TimW MajorGeeks Administrator - Jedi Malware Expert Staff Member

  3. brownizs

    brownizs MajorGeek

    I wouldn't. That cord is usually only 16ga stranded, and only good to hold a trunk closed. Get a power surge strip, not that junk.
  4. Digerati

    Digerati MajorGeek

    I agree with TimW. That will work just fine. As you noted, your PSU is rated at 460W, way below the 1650W limit - especially since it is very rare for the computer to draw anything near that 460W. Now if you start connecting monitors, speakers, and other devices to that cord too, then you may have a problem.

    I disagree with the suggestion to use a surge and spike protector. They are little more than fancy and expensive extension cords that do nothing for extreme high voltage anomalies except shut off power, which is very bad for high speed digital electronics (not to mention for the data on the hard drives). For all other high voltage anomalies (surges and spikes), they simply chop off the tops ("clamp") of the sinewaves - leaving a "dirty" mess for the PSU and motherboard regulators to cleanup. And cleaning up power takes power - thus increasing heat generation in those devices. Not good.

    And surge and spike protectors do absolutely nothing for low voltage anomalies. Nothing at all. These anomalies include dips or dropouts (opposite of spikes) and sags (opposite of surges), and brownouts (long term sags). Any of those "events" can and will strain the regulating electronics as they attempt to compensate for those irregularities.

    Note that surges and spikes don't just originate outside the house from the power "grid". ANY high wattage appliance can generate surges and spikes. These devices include ovens, microwave ovens, refrigerators, air conditioners, water coolers, toasters, coffee pots, and $10 1500W hair dryers from China! So if you have any of those type devices in your home or office (and who doesn't?) or if you live in an apartment complex, your computer should be on a "good" UPS with AVR. In other words, all computers should be on a "good" UPS with AVR - regardless if you live in Tornado Alley (like me) or not.

    Note a nice 1300 - 1500VA UPS will support a big computer (i7, 8Gb of RAM, and 3 drives), modem, router, switch, phone, and two 22" widescreen LCD monitors for over 20 minutes. And if I immediately shut down my computer and monitors, my UPS will carry all my network devices (thus retaining all my IP assignments) for at least 4 hours.

    So don't waste your money on surge and spike protectors and instead, get a "good" UPS with AVR - automatic voltage regulation. A "good" UPS with AVR will use its advanced power regulation circuits and batteries to boost power during low voltage anomalies and it will "clamp" but reshape the power signal during high voltages events.

    Note I have mentioned nothing up to this point about backup power during a complete power outage. That's because backup power is only the icing on the cake. It is the regulation that is the UPS' bread and butter.

    And like PSUs, there are cheap UPS you need to avoid. A cheap UPS may not regulate the power very well, but more importantly, cheap UPS may not react to power anomalies quick enough. According to the ATX12V Form Factor PSU Design Guide, a computer PSU needs to "hold-up voltage" for just 16ms in the event of an outage or dropout. 16ms! The blink of an eye takes about 150ms. So a UPS must be able to react, analyze, and cut-over power or regulate power very quickly, cleanly, and efficiently. A cheap UPS may struggle, at best, in that area.
  5. gman863

    gman863 MajorGeek

    Although you may already know this, one of the biggest dangers with extension cords is setting things on top of them.

    Never run an extension cord under a chair mat or carpet runner. This can cause friction that, over time, may cause the cord to short or overheat creating a fire hazard.

    The same goes for placing cords under any weight-bearing object. The cord should be kept out in the open (such as running freely along a wall) to avoid crushing the wires and overheating.
  6. Goldenskull

    Goldenskull I can't follow the rules

    Just make sure you keep an eye on the power cord any sight of high heat is very dangerous could cause fire.
  7. Digerati

    Digerati MajorGeek

    Or a couple fingers! On any extension cord, the connectors are where heat will show first if too much current is being drawn through it. So tax (sitting idle is not taxing) your computer, then feel the plug at the wall every 15 minutes or so. A little warm is okay. Very warm to hot is not. But again, it is just a 460w PSU. And besides that, it is unlikely your computer (the CPU, motherboard, RAM, drives, graphics solution) draws from the PSU anything near that. Certainly not for any sustained amount of time.

    And power supplies only draw from the wall what the load (the computer) demands, plus another 20 - 30% (wasted in the form of heat due to PSU inefficiencies). So you are way under the line here. At least until you get a "good" UPS with AVR! It will have a heavy duty cord. ;)

    Good tips on running the cord. Another is to ensure it does not become a tripping hazard.
  8. Speculant

    Speculant The Confused One

    That's exactly what I currently use to power my PC (our house is also old, and has no 3-prong outlets), and the PSU on mine is "rated" at 500 watts. Running for 6 months with no issues.
  9. Digerati

    Digerati MajorGeek

    My house is 52 years old and some has been re-wired but there is still some 2-wire outlets. And that's fine, if you have a good ground at the breaker/fuse box, and the wires are still securely fastened (on both ends). And outlets themselves need to still be good. All outlets wear out over time - from friction from the plug prongs, but just tension in socket weakens. Loose connections at the wall can result in erratic behavior by your computer, or worse, an overheated outlet. So check that.

    Also, to minimize "noise" in the audio and video, I recommend you ensure your computer, monitor, speakers, and everything else that connects to your computer all be powered out of the same wall outlet. This ensures they are all at the same "potential", which help minimize interference problems. The same recommendation holds true in more modern homes, but they offer better grounding from the start.

    BTW, before this portion of the house was rewired, I wired a #10 solid copper ground wire to the wall outlet box and clamped it to my cold water inlet pipe. Then I replaced the 2 prong outlet with a 3-prong which then provided a good "real" ground (Earth) for my computer. My UPS stopped yelling at me for having an open ground too.

    For anyone considering this, home improvement stores sell the solid copper wire and the proper (to code) clamps used for attaching solid copper wire to water pipes. Just make sure it is the cold water. Hot is often isolated through the glass (an excellent insulator) water heater. This assumes you have copper pipes - and I am guessing you do. And before you assume the outlet is safe, check it with a AC Outlet Tester. I recommend one with a GFCI (ground fault circuit interrupt) indicator as it can be used to test bathroom and kitchen outlets too. These testers can be found for your type and voltage outlet, foreign or domestic, at most home improvement stores, or even the electrical department at Walmart.

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