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Question DetailsAsked on 10/29/2017

Power strip is acting as a ground

I just moved into an old apartment with an old electrical system. Some of the outlets are two pronged most are 3 pronged. When I plug in a power strip in a 3 pronged outlet on the circuit my room is on, the ground light won't come on, and when I use a tester it doesn't show a ground.

I assumed that the circuit didn't have a ground. Just now I plugged in another power strip into the same outlet but it was off. As soon as I plugged it in, the first power strip's ground light came on. When I use the tester in the 1st power strip outlet it shows a ground is present now. If I turn on the 2nd power strip or unplug it, the ground light disappears from the tester. What is causing this to happen? Is the second power strip acting as a ground? (Will current leakage flow through the second power strip?) Or was an outlet on the circuit wired incorrectly and is affecting all the outlets downstream on that circuit?

I will get the landlord involved, but until then I'm curious what is happening

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1 Answer


You say you used a "tester" - assuming a plug-in LED type where the LED's light (or fail to) in different combinations to show wiring issues ?

Unless the act of plugging and unplugging the surge protectors just happened to cause the ground to make contact (loose screw), my guess is ALL your outlets are ungrounds - all 2-wire,and someone jsut used modern 3-wire outlets for replacements. I would bet your tester shows no ground on all the outlets in the apartment - though it is possible that a ground was added on just one or a limited number of circuits in the past as an upgrade.

You could pull off the cover plate (carefully to avoid shorting it out) and look with a flashlight to see if there is a ground wire connected to the green screw on the outlet - if so, probably ground system is in there, though would take a volt-ohm meter to prove you actually have a ground connected.

My guess - the first power strip correctly did not detect a ground so the green light did not light (sounds like a Tripplite strip) - but when you plugged the second one in, it created an apparent ground connection because it is a surge-protection strip and possibly also has EMF filtering for USB - so the surge protection electronics created a connection from neutral to ground - either because they are wired that way (usually are) or because the surge protector has failed/blown out and is connecting neutral to ground. This created a neutral to ground connection in the plug strip nd outlet - which normally might not carry any significant amount of power but is detectable by the tester. Note this would NOT be a "ground" because it is just connecting ground and neutral wires in the plug strip and (when plugged in) the outlet - but the only connection to the breaker box would be through the neutral wire, not a ground wire, so not really a "ground".

I would guess the detector will, with first strip only plugged in, shows no ground when plugged into the power strip too, but with the second one plugged in at same outlet does show ground present when plugged into either strip.

If the tester shows no ground when plugged into either the outlet socket or into the first strip (second one not plugged in), it is probably telling you the right thing - no legitimate ground, and even if it shows one with second strip plugged in I would not count on it - because that might just be the ground connection for the electronic protection circuit elements showing up, but it probably cannot carry any significant amount of current without frying so is not really and real protection against a short or major surge.

If that is the case, might be a problem getting a ground isntalled - because that would mean rewiring a circuit from the breaker box, or perhaps putting in new wiring to a new single outlet which would be grounded - not an uncommon thing in older apartments where they provide one grounded "office equipment" outlet for computer/ printer/ electronic device charging and surge protectors - sometimes also tying in the normal TV location for TV and video games and such. But does run several hundred $ commonly - more in the $500 range in cases where there is not an easy way to run the new wiring from breaker box to the outlet location. Some cheap electrician will shortcut by grounding to a nearby metal water pipe but that is neither legal nor safe - can in fact result in a short causing electrication of your water piping and appliances - I have run into cases where enough juice was in the water system that a person got electrocuted, because there was a non-metallic component between that point and metal pipe in the ground, or the supply line was non-metallic. (Clean water itself is a poor ground - grounding to piping counts on the metal piping acting as the ground conductor, which can also cause corrosion of the piping - a bad practice though standard before - what, maybe 1970's or 1980 era ?)

If they will not do that or want too much $ for it, your next best bet is a GFCI outlet - gives you at least some protection against shorts and is cheap to install - but has the downside that some surge protectors intermittently trip out GFCI breakers when the dissipate a surge because they geanerally do that by dumping the surge energy to ground - which the GFCI picks up as a mismatch between incoming and outgoing power on the live and neutral wires so it trips. Can be VERY frustrating - I fought that for weeks in my house thinking the surge protector or computer was a fault, then it went away when I changed surge protector brand.

Answered 2 years ago by LCD

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