Two-Prong/Three-Prong Ground in Apartment


Old 10-28-04, 11:31 AM
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Two-Prong/Three-Prong Ground in Apartment

I've been doing some reading on this forum and elsewhere about the
common two to three-prong issue. I suppose i'm just looking to confirm
my thoughts.

I'm currently living in an apartment where both the building and wiring are
fairly old. The outlets in the apartment are about half/half two-prong and
three-prong but only the three-prong outlets in the kitchen, bathroom and office are properly grounded. This leaves the livingroom and bedroom open.

I have two APC professional series surge supressor - one for the computer and one for my home audio/video equipment. Since the office wiring is properly ground the APC doesn't show a ground fault, so my PC should be protected... at least to the capacity of the APC unit.

In the living room there are two available outlets. The first offers a three-prong outlet with an open ground. As expected, the APC unit indicates a ground fault present here. The second outlet is two-prong - this would have to be swapped before the APC can even be plugged in. Obviously, I need a way to ground the outlets in the livingroom. Being an apartment, it's kinda tricky.

I discovered something interesting tho. Since the APC units are of the "professional" variety they offer protection for video and telephone equipment as well. With the APC plugged into the three-prong outlet in the livingroom, the "ground fault" warning LED goes out when I connect the coax for the cable television.

Can it be that the television cable offers enough of a ground to protect my equipment and permit the APC to do it's job? If so, can I simply replace the other two-prong outlet in the livingroom with a three-prong and have the coax function as a ground? I'm willing to bet this isn't recommended, but what else are us apartment dwellers to do? GFCI? Suggestions?
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Old 10-28-04, 11:44 AM
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Location: Central New York State
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Your living room receptacle should not be three prong, since no ground is present. I would have the owner correct the problem. And make sure that it is done the right way, by properly grounding the receptacle.

I bet that a properly worded letter from your attorney will get the receptacles throughout the apartment grounded properly.
Old 10-28-04, 11:55 AM
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I haven't actually discussed the issue with the landlord/owner as of yet so I don't think a letter from my attorney is entirely appropriate at this stage.

I'm just curious to know if/why/how the coax is introducing a ground and if it's "safe"... for both me and my equipment.
Old 10-28-04, 12:01 PM
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The coax is grounded and it is grounding the APC. This is probably sufficient for the APC, but it doesn't allow the installation of a 3-hole receptacle according to US electrical code. One problem will be that any surges of electrical power will probably be dumped to the coax. That may not be what you want.
Old 10-28-04, 12:15 PM
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Location: Central New York State
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You're right, I was jumping ahead to what you need to do if your landlord refuses to do the work.

At the very least the improperly grounded receptacle needs to be converted back to being a two prong receptacle or it needs to be converted to a GFCI receptacle and marked "No Equipment Ground".

If you do continue to use the APC on this circuit that is not grounded except through the cable line, I would make sure that you use a similar APC on every TV or piece of equipment that you want to connect to the cable. As John said, a surge may be dissipated via the cable ground on the coax. You would want to keep this from any of your devices.
Old 10-28-04, 02:21 PM
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Indeed, any audio/video equipment connected to the coax would be connected to the protected outlets on the APC. Are you saying that damage could still be done? In the event of a surge would it be dissipated via the coax to the street or to my television!?! This may be a question for APC.

Obviously I, and my landlord, need to take a serious look at a permanent solution. I don't see it being an easy job, fishing new ground lines from each outlet to a common ground point in the building (only two floors).

Thanks for the comments.
Old 10-28-04, 04:47 PM
L Elwood
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Do Not use the coax shield as a grounding conductor, in the case of a fault the ground conductor will carry many THOUSANDS of amps for as long as it takes your breaker or fuse to open the circiut, this could be several cycles depending on the device. the total ground fault current will depend on the impedence of your utility's distribution equipment. As was said before change your outlets back to the ungrounded type, and try to convence your owner to upgrade the wiring. Take care, Lee
Old 10-29-04, 07:20 AM
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This may be an easy fix. If there are properly grounded outlets in other rooms, there is probably a ground conductor of some type already in place throughout the building. It may be that the plug in the living room needs to be wired to the box or connected to an existing ground wire that was left open somewhere. Since this is an apartment, you may not do any of this work yourself. Talk to your landloard and see if he/she will bring in an electrician. As an ex-landloard, I would not have had any problem doing this for a good tenant.

Doug M.

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