If i use one ground wire for two outlets, will my equipment get damaged?

Here is what I want to do:

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If my air conditioner sends voltage through the ground wire shared with the outlet powering my computer, would my computer short out and or get damaged?

  • Possible duplicate of Is it OK to borrow a ground wire from a different circuit? Commented Jun 29, 2016 at 15:38
  • 1
    Just to be clear here: You have two 3-prongs in different boxes, but on the same circuit and you want to know if a ground fault on one will affect equipment on the other? Commented Jun 29, 2016 at 16:01
  • Where is this ground coming from? A wire in the cable? A separate ground you run to a cold water pipe? Other?
    – Yehuda_NYC
    Commented Jun 29, 2016 at 19:42
  • Just get a UPS with an always on battery and call it a day man. Commented Jul 31, 2016 at 3:26

2 Answers 2


Generally, adding a ground wire is always better for electronic equipment. It helps surge suppressors do their job by providing a ground reference. It provides real chassis grounding which among other things gives a solid route for static electricity to go to ground instead of getting inside equipment. It also provides a fault path if any hot wires short to ground, which assures you get a breaker trip. And it makes sure equipment chassis is not energized so it electrocutes someone. I'm glad you're doing it - it will help.

That said, grounds will not cause cheap electronics with poor components to suddenly become quality. Grounds will not themselves "clean up" dirty, noisy AC power, although they will help surge suppressors do that. Dirty power is often caused by your own equipment - for instance the air conditioner in your drawing. You may want to protect the PC from the air conditioner.

Grounds also don't fix potential overloads, and you might have one here. Fancy PC's aren't necessarily power hogs (the Mac Pro is only 2.5 amps) but "850 watt" PC power supplies are popular and they can draw 10 amps full bore (the difference being inefficiency). A typical window air conditioner is 5-8 amps. Loads which are continuous should only run at 80% of circuit capacity, that's 12A on a 15A breaker and 16A on a 20A breaker. I would encourage you to investigate further to make sure those loads (and the other loads on that circuit) aren't too much. To measure a device's actual current draw, gadgets like the Kill-A-Watt do nicely.


I think your concern is justified. It is not uncommon to see a AC window unit dedicated with its own receptacle. This is because of substantial startup current to get the thing a juggin'...

Always consult the manufacturer of the appliance in question. Generally they will tell you if it's okay or not to share with another small appliance.

For general non-critcal computing with a small footprint you're probably ok with a small window unit. But if you add a laser printer on the same circuit....forget about it!!


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