Does anyone have an opinion (good or bad) about those adapters to convert ungrounded 2 prong outlets for use with 3 prong appliances. I know that GFI’s (with the ungrounded sticker) are an alternative but to convert most of the outlets in the house would be expensive. Are these adapters suitable or are they dangerous?
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_IF_ the wiring is in metal conduit and _IF_ the conduit is continuous from the receptacle box back to the main panel and _IF_ the couduit connections are good, then you might get the funcytion eqyuivalent of a grounded circuit, but it wouldn't technically meet code in most (all?) places.
And I'm sure that there are electricians who, knowing more about it than I, will tell you even that isn't good enough.
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Years ago my ex FIL who had a lot of rental property would take the old two prong outlets out and change them to grounded, he would "jump" a wire from the white to the ground. It would pass the test by the rental inspectors(using those little yellow testers). Always wondered if that was dangerous or not.
I figure some electrician will let me know.
Yes, that was more dangerous than leaving the ground unconnected.
They're dangerous. Unless you open up the outlet box and check, you have no assurance that the center screw or anything else in the box is grounded. (Even checking inside is a little iffy, since electricians in the 50s and thereabouts would often leave grounds unconnected at junctions.) Most stuff prior to about 1940 is pretty much guaranteed to NOT be grounded.
If you need to temporarily connect grounded equipment, buy a contractor's GFCI box -- a GFCI built into a short extension cord. This can be moved around to wherever you need it.
The adapters don't make a connection to ground, they just provide a hole for the ground prong to fit in. Using an adapter is electrically equivalent to just ripping the ground prong off the plug.
It's not the safest option. If a particular appliance were safe without the grond connection it would only have a two prong cord, like a double insulated tool or a desk lamp. Ground connections provide a back up for appliances which don't have alternative safety features.
For example, a washing machine or a clothes dryer; if the hot wire inside the appliance comes loose and contacts the metal frame, or there is a short within the controller, the cabinet of the appliance would become energized, and that would be dangerous. If the frame is grounded (through a grounded cord plugged into a properly wired grounded outlet) then the frame would not become energized with a dangerous voltage, because the stray current would be carried by a good connection from the frame back through the building wiring to the earth.
Using an adapter is better than ripping the ground prong out because you can use the ground prong in the future in an outlet that has a grounding receptacle, but while using the adapter you put yourself in a position of loosing protection the ground is intended to provide in a grounded system.
Surge supressors must be grounded to work. They need the ground to have somewhere to send the surge to. If they are plugged into an ungrounded outlet, they don't provide any surge protection except tripping an internal circuit breaker, which won't protect against really high voltage surges (they just jump the gap inside the breaker).
WayneL,
Most of your points are good but I would like to clarify "because the stray current would be carried by a good connection from the frame back through the building wiring to the earth."
In the case if a short circuit, the function of the green wire is to carry the current back to the panel. This causes the anps going thru the circuit breaker or fuse to go from a piddling 4 or 10 to thousands causing the breaker or fuse to blow instantly. The earth or ground rods have nothing to do with this.
If you want to get technical, the ground rods have a resistance of 25 ohms or more. Using 120 volts and Ohm's Law [E = I times R] [Volts = Amps X Resistance], you would get maybe 4.8 amps flowing thru the ground and then added to whatever is already flowing thru the breaker. It is likely that the breaker will not trip.
~Peter
Your clarification is helpful. If there is a dead short of a hot wire to a grounded frame then the fuse or circuit breaker would blow and the hazard would be gone. On the other hand, if there was only a poor short to the frame, say from corrosion crud bridging, moisture, or deteriorating insulation, the frame could be energized to a voltage high enough to give someone a shock, but still not draw enough current to trip a breaker.
I found a wierd situation once helping some friends at a non-profit organization. The electric bill was routinely much higher than would be thought since the building was only occupied a few hours a week, was only a few years old, and there were no high wattage appliances in the building. I checked out every appliance and circuit until I came across a mysterious wire attached to a screw on the back of the very old refrigerator which ran into the electrical outlet box and was connected to the ground screw. A clamp-on ampmeter showed a slight current through the mystery wire. When I asked what that wire was for they said that the refrigerator kept giving people shocks when they touched the handle, so they grounded it.
I politely explained that there was a partial short in the fridge that was putting voltage on the frame and handle, that's why people were shocked. By attaching the ground wire they were directing that leaking current to ground. It was therefore safe, but they were paying to send a constant flow of electricity right into the ground.
When the problem was fixed there was a substantial reduction in the electric bill.
>> ... kept giving people shocks when they touched the handle, so they grounded it.
For every problem, there's at least one solution that's simple, obvious, and wrong.
>>The adapters don't make a connection to ground, they just provide a hole for the ground prong to fit in. Using an adapter is electrically equivalent to just ripping the ground prong off the plug.
It depends. If the circuit is two wire rag non-metalic, you're right. If the circuit is 2 wire in metal conduit, the adapter can (if everything else is right and the stars properly aligned) make a connection to ground using the conduit as the ground path.
That does not meet code, though.
_______________________
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Thanks to Jeff and David and Jim and Rich and Steven and Mark and Jason and Shep and Jen and Mike and Joe and Bill and Ken for their offers!
Several donations have arrived! Thanks and God bless!
You're right. What I said is not correct if there is a ground path through the outlet strap to the box, through the sheath and back to the panel. I chose not to say that to keep the reply shorter and possibly less confusing to someone not all that familiar with electric wiring.
But yes, a grounding adapter is better than ripping the grounding prong off a cord if there is a connection through the sheath, etc., back to the panel.
I have one of these adapters on a receptacle I haven't gotten around to changing. The box is metal, as is the conduit to the circuit panel. I get a light when touching the probes to both the "hot" slot and the outlet cover screw, so I assume that the box is grounded. The cheater adapter has a flat, copper ear that fits beneath the outlet cover screw. When the adapter's plugged in and the copper ear is attached, I get positive readings with my circuit tester. Though this temporary situation is not acceptable for electrical code, I would consider it nonetheless safer than if that copper ear weren't connected or if the box weren't grounded.
The loads that that don't mind not having a ground usually have a two prong plug. Clock radios and such. These impose a very limited load and should cause few problems with your present system if it is in decent condition. Check for receptacles so loose that plugs fall out. Ungrounded receptacles, commonly known as mutes, are available.
Appliances with three prong plugs, like Window AC units, refrigerators and computers, usually, given the likely age of the wiring, are better fed with individual circuits. Even in new construction as these are usually larger point loads or need, as in the case of the computer, a solid ground as a voltage reference and a drain so a surge arrestor will work well.
A GFI, upstream of other receptacles on the circuit, will help with the safety issue of not having a ground, getting shocked, but will do nothing to get a surge arrestor to work. Without a solid ground to dump the overvoltages into a surge arrestor is just an expensive power bar.
Options. Cheapest to most involved.
Live with it as-is and be assured that most times firemen are not in your future. Learn to think of the dimming and flicker of the lights as a quaint foible of an older house. Expect delicate appliances to fail a little early. The computer may be a little more glitchy or may fail entirely during thunder storms or utility switching. Thousands of homes are like this and only a few burn each year and insurance companies might cover replacing the mother board on your machine.
Second you could rewire critical or most heavily loaded circuits. Kitchen circuits, a computer circuit and one to the baths for the blow driers are a good start. A fraction of the cost of a complete rewire this can get you reliably into the 21 century. As money becomes available more circuits could be run, like to the entertainment center. At some time you will likely need a new panel and usually a new meter can. Don't go any lower than 200A without a dire reason.
Third is a complete rewire. Do it all at once and the price per circuit goes down. It will be expensive. Be sitting when you get the estimate. This is usually more than wiring a new home because the wall and floor finish it in place and will need working around. If done well it will get the family by for another 60 years. Maybe longer and might lower your homeowners insurance rate.
I didn't include running a ground to each receptacle because by the time you get a wire in you, just as easily, could have pulled in a new cable. It is a false economy. Seeing as threading the cables in is about 80% of a rewire job you would be spinning your treads. Spend a little more and rewire part, or all, of the circuits. Live with it until you can get the cash together to do it right.
it all depends on how your house was origanally wired
my house had 2 prong outlets, if u looked inside, no ground.
when the house was wired the ground conductors were connenected together and to the metal box.
bobl Volo, non valeo
You should only need to replace the outlets with a GFCI at the first outlet in the series. The outlets down stream from the GFCI on the same circuit will all be protected by that GFCI if it is installed correctly. I don't know how many circuits you have, but figure $12 - $20 per circuit, and you will be about as protected as you can be without rewiring your house. You can then replace the outlets with standard three prong outlets. According to code there is a sticker included with the GFCI stating that the outlets are not ground protected which you may have to put on if there is an inspection involved. I would not put the GFCI on a plug controlling a freezer or refrigerator, as that can cause some problems if it trips and you are not around.
jim