Both circuit testers and meters will not test for a reliable ground because the test at a very low current. What tests good at low current may be high resistance and not be an effective ground. Actually a 100W lite bulb from hot to ground is more accurate - or measuring the voltage across the bulb.
GFCIs compare the current on the hot and neutral wires and trip if there is a 5 mA difference. They do not need and do not use a ground wire (the ground connection goes to the outlet only).
The outlets that got replaced already seem to have new wire runs as well. These outlets are connected to beige flat cables (I think this is called Romex). The older/original wiring is going to metal boxes. This cable looks to be a rubbery substance covering some kind of mesh. The cable says Citex NON METALIC COVERING. I have pulled one of the older outlets, its in a metal box with four wires coming in (two black/two white).
This was the case in my 1959 house. Two prong receptacles. I took one out and there was the ground wire (smaller guage, as mentioned above). So the house has 3 wire cable. So I just replaced with three prong outlets and connected the ground.
Get a home wiring book from your library. You will learn quite a bit there.
No one who knows what they are talking about will tell you that what I'm about to suggest is required by code but I'm going to suggest that you use isolated ground receptacles for your replacement receptacles that will be supplied from the Ground Fault Circuit Interrupters. The reason that I suggest this is that with metal boxes and especially with older armored cable that does not have a bonding strip a fault on any plugged in load can energize the other three wire loads that are plugged in or metallic fixtures supplied by that circuit.
Isolated ground receptacles assure that any fault is isolated to the defective cord and plug connected load rather than having stray voltage present on the rest of the ineffectively grounded or ungrounded circuit. You still label the receptacles as having no equipment ground. The code already requires that no equipment ground connection be made to receptacles that are installed from an ungrounded GFCI protected supply but the connection between the receptacle grounding terminal of a regular receptacle and it's yoke make that instruction ineffective at isolating the receptacles from each other.
Once again this is not a requirement of any code I am aware of but it will reduce the chance of electric shock. The reason for being so careful is that GFCIs will only protect older children and adults in good health. Smaller children and adults who are old enough or sick enough to already have an irregular heart beat can still be killed by electric shock. Even healthy adults can be injured and even killed by the physical reaction to the momentary electric shock that occurs before the GFCI opens the circuit. Electric shock causes muscle contractions that can result in falls or other dangerous involuntary motions.
If it was built in the 50's there is a good chance it has BX, which is a metal spiral around the wires. Since they didnot have plastic boxes back then, I assume you have metal boxes, Therefore you have a ground. TEST THEM ALL TO BE SURE.
You need to run a green pigtail wire from the box to the outlet. Those older metal boxes did not always have a hole for a ground screw. Get a ling enough drill bit to drill holes in the rear of the boxes. In the electrical dept, they sell an alectricians multi-sized tap. But one to thread the holes, OR get self tapping screws with a hex head and use a nutdriver. I believe the green ground screws are a
10-32 thread (I may be wrong). Be sure you dont chop up the wires with the drill chuck.
Here's a tip. Shove then in a piece of small sized hose and bend them upward. That's my own "invention". I always keep a few pieces of 6" gas line hoses in my electrical toolbox. just for that purpose, and they have come in handy a few times when I opened a box and found bad wires, but needed to keep the wires live to test to find the source. Just slip them over the wires during the tests. (not premanently - replace all bad wires). I also used them a few times when working on a live circuit with lots of wires. Helps keep hands away from the ones you are not testing at the time, without having to bend that old insulation so much. Just slip the hose over the wire ends.
There are two types of Armored cable. One is BX that was built in General Electrics Bronx plant; hence the designation BX; which has no bonding strip inside the armor. The other is a product of later manufacture that has a bonding strip in the armor and is more properly referred to by it's electrical code designation of AC. BX is not suitable for use an Equipment Grounding (Bonding) Conductor. The corrosion between the turns of the armor makes the impedance of the return pathway too high. Before you try to use the armor of the cable in your walls as an EGC you will need to check for the presence of a bonding strip. If there is no bonding strip then you will need to protect the circuit with a Ground Fault Circuit Interrupter. When unbonded BX cable carries fault currents the result is often a fire due to the heating of the armor.
You are correct, but I believe in the 50's they all had the bonding strip. and BX was always the trade name even though you are correct about the AC which was always a confusing term considering the power is AC, thus is probably whey they kept the BX terminology.
Just curious, does anyone know what both BX and AC stand for?
A note to the OP. If you have a dedicated outlet for a computer or other device that requires a good ground, if you dont want to replace the cable, you can always run a green wire alongside the armored cable. Whether this ia acceptable to code is questionable, but it will get you a good ground (if taken all the way back to the main panel).
Ok, here's an outside the 'box' alternative- how to remove paint from outlet covers/faceplates. Get them wet, scrub with copper wool- I've done it. So no need to replace anything. Really, though, you want to have properly grounded circuits. It's safer. You've gotten some good suggestions- but why not just call an electrician, get a free estimate. Sometimes your local hardware store will give you a few names of local, reliable people if you don't know any. This way, you'll have the situation looked at, get cost estimates, recommendations re minimal/ ideal upgrades etc. You'll actually have an experienced person familiar with local construction look at your wires, as none of us can do. Then you make your decision.
Grounded outlets are not really needed in all rooms. For rooms with lamps, tvs and stuff - not needed.
For computers, air cond. kitchen appliances and the bathroom ,they should be grounded. Often new wires can be run to those places if there is a basement because these rooms are often on the first floor. You lighting can stay as it is. Sometimes its easier to just add new outlets and only rewire the kitchen area. You can still buy non-grounded outlets too. They cost more.... go figure !!! If you got a garage or basement workshop, rewire them - they are usually exposed so easy to change. In a 50's home, the basement is likely conduit wired. Thats definately a good ground unless someone pulled the pipe apart.
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