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By considering things like energy-efficient mechanicals, window orientation, and renewable energy sources, homes can be evaluated to meet the energy codes. Here's what the IRC has to say.
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"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
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Paul, it's usually a rewire, not just an outlet change.
*You can take out the old outlet and put in a GFCI outlet. This is a halfway measure, but it's better than nothing. And it's OK by code.
*Tom,Why do you have to use a GFI outlet (instead of the standard type)?
*You don't HAVE to use the GFI. But you can use the GFI if you don't have a ground connection.Thus it is useful for reto applications where it is hard to change to a wiring system with a ground.It give equivalent safety, but it does not provide a ground for things like surge protectors.
*Of course.... not to insult your intelligence.... but you wouldn't simply take out the two-prongers and install the three prongers now, would you? (This would be stupid, dangerous, and illegal).Like George said, it's usually a case of a complete re-wire in order to provide a ground conductor for the receptacle and box. There's no other way to provide a real ground for that third prong.Good luck,Scott.
*b TVMDCIf it is a retrofit, the chances are there is either flex or conduit in the wall attached to a metal box. Wouldn't the receptacle mounting screws provide a ground? Or a Green pigtail to the box?
*Yes. If all is connected from the panel right. If it's BX, and the metal sheathing is grounded, just work from the metal box. Jeff
*Ok, help me out here. My house is 50 years old. I noticed that the romex used when the house was built has a copper ground wire in the bundle. At the point where the romex enters a box the ground wire is wrapped around the romex so it makes contact with the metal box via the cable clamp. I'm not an electrician but this look a bit dubious to me. Some outlets have been changed over to a three prong, a few two prong are still in the house. Just by shear luck I've changed over a few outlets when I purchased the house and used GFI's because some one gave them to me. Checking the house last night, about 50% of the house's outlets are now protected by the GFI's. After reading this discussion I'm concerned about the safety issues.I'm going to bring in a liecenced electrican to check out the wiring. But I'd like to get a handle on the situation before I bring him in. Is there a way to check to see if the three pronge outlets are propely grounded?Thanks for the help.Jay
*i Is there a way to check to see if the three pronge outlets are propely grounded? there is a simple tool for checking this. Don't remember the "official" name. Inexpensive. Checkout a good electrical supply house/department.
*Jay, if you have ground wires in the receptical box you can very carefully wire nut them together along with another piece of bare copper about 8" long. This is called a "pig tail" The loose end of this pig tail get connected to the ground screw on the receptical. This is only effective if the grounds of each run are connected properly back at the main panel. Your electrician can check this out for you, make dam shore he dose! It was common practice for the old-timer electricians to wrap the ground wires around box clamps. Please be very carefull.A friendly tradesman can help point you in the right direction, don't skip that part. Bill
*Continuity should exist between the neutral prong and ground prong. The potential between the neutral and ground should also be 0 volts. If this reads other than zero make sure your circuit ground connects to an earth ground (cold water pipe or ground electrode).
*5 other messages on same post earlier, repeat one here:To reinforce the grounding need, saw an electrocution case history a few years back about a room air conditioner that would fry even those of us who tested circuits with fingers when we were young and dumb. Seems the junction between the run capacitor and motor winding (cap run motor) was shorted to the chassis, no ground wire. The LC resonance resulted in 370 V at the junction, which put the case at 370 V also. One dead homeowner. b If you put in 3 prong outlets and tied a number of just the outlet ground screws together without having a good "real" ground, you could make every chassis on the string a hazard.
*Art:I can see how tying bond wires together without a path to ground will make all the cases hot, but what is LC resonance and how did the voltage climb to 370V?Thanks,Scott.
*Go to any store that carries electrical supplies. Radio Shack probably even has them. The tool is a simple three prong plug, with three little lights across the back. The light light and let you know the deal. The code to the lights is printed right on the plug in device. These are under $10. For about $20, the same thing , but with a GFCI test button built in is available. I just call them receptical testers. They'll know what you mean. Jeff
*RE: Receptacle testers. These little devices are ok for spot checks on whether 3 prong outlets are grounded or not, but they will not detect the so called bootleg ground where a jumper wire has been connected between the neutral terminal and the ground screw.(This is a dangerous setup).I have seen many of these in older homes where someone has replaced the receptacle and bootlegged the ground to "make it test right". Use the tester, but also pull the receptacle to check the wiring.
*Check out the information and diagrams converting 2 prong to grounded 3 prong receptacles at: http://www.codecheck.com/250_50_commentary.html
*Norml,Concerning the "bootleg" set-up you just described. I too have seen this. What exactly makes this dangerous? The neutral wire leads back to the bus bar in the panel box, and a regular ground wire also leads back to this bus bar. In a 2 wire, non-grounded system, such as "knob & tube", By attaching a pigtail of bare copper to the ground screw on the receptacle and back to the neutral wire on the other end, what is the danger? Please advise. Thanks.Davo.
*There is some conflicting info on this thread about the legality of this work. I'm interested because I have a 50yr old house and I'm 1/2 way done changing all 2 prong to 3 prongs. All outlets were run with BX, and I am doing a grounding tail to the metal boxes. They all test good once complete, so I'm confident they are grounded well.I ran this by a local electricain who's opinion I trust, and he says perfectly legal.Is he wrong? Is this a local jurisdiction issue, or is this universally accepted or unaccepted?Thanks,Stray
*Scott and Davo: One of the dangerous scenarios was described in #12. A variation of that is that the Airconditioner motor winding gets burnt out (possibly burning down your house)with the bootleg setup or the case is hot (120 only) even with the A/C off. Remember Murphy, anything that can go wrong will. Consider scenarios where the white and brass screws get interchanged by the same bootleg installation. LC resonance-tried to explain in a few sentences, best to look LC resonance (also search power factor/ reactance/impedance) up on the web or in library, some of the .edu sites have good tutorials. I tried to do it in electrical terms in a few sentences, but realized it would just become more confusing as most of the terms used may also require explanations. Visualize your truck with bad shocks on a rutted road where at a certain speed the truck just keeps bouncing and the bouncing keeps getting bigger - that is a mechanical equivalent of LC resonance.The L is the springs, the C is the weight of the car, the shocks are the resistance, the small bumps in the road are the voltage which get amplified as the car suspension resonates with the small bumps.
*Davo - It is a violation of the NEC to connect the "neutral" and ground conductors at any point beyond the service entrance. As two examples of the danger involved, consider the following scenarios in which a two prong receptacle is replaced with a three prong receptacle with a bootleg ground:1. Someone decides to tap in to this circuit upstream of the receptacle. Through ignorance or accident, when splicing things back together, the connection is made black to white. The ground lug of the receptacle is now hot. Plug in a lamp, everything is OK. Plug in a washer, the frame is now hot, and if you touch the frame and something grounded, you're toast. Sound farfetched? I have seen exact setup before.2. A grounded appliance is plugged in to the receptacle. For some reason the white wire comes loose between the receptacle and the panel - not uncommon if the push-ins were used. The current will now try to return to the panel via the appliance frame and earth - and you if you provide the path to ground.Bootleg ground? Very dangerous!
*>Continuity should exist between the neutral prong and ground prong. The potential between the neutral and ground should also be 0 volts. If this reads other than zero make sure your circuit ground connects to an earth ground (cold water pipe or ground electrode). It is normal for a small voltage to exist between neutral and ground when something is turned on and current is flowing through the neutral. Usually it's fractions of a volt. This is caused by the resistance in the neutral wire between the load and the service entrance. If you find this voltage, you can't test for continuity with a meter. The ohm meter function works by putting a voltage across the item under test, and seeing how much current flows. The presence of any other voltage will either make the reading incorrect, or damage the meter (mostly that happens with the old fashioned analog needle meters.)If you use a high impedance volt meter to check for voltage between hot and most any piece of metal, you might get something close to line voltage no matter whether the thing itself is truly grounded or just floating. Stray capacitance is enough to get you that reading with a meter impedance in the megohms. Strap a resistor across the meter, say 1k or so, and you'll get nearly nothing between a floating item and either hot or ground. That proves that it's floating. The resistor, BTW, will dissipate about 15 watts when it's across line voltage, so it'll get hot after a while. Don't try this with a 1/8 watt resistor. ;-)If something -- a box -- tests grounded, that's nice, but it doesn't mean that it's legally up to code grounded. To prove that, you have to trace all the way back to the service entrance and see that all the ground connections are OK. The ground path has to have a low enough impedance that if a hot touches it, enough current will flow to trip a breaker. Something can test grounded, but if you actually put a hot in contact with it, something down the line may arc and open up before the breaker trips.-- J.S.
*Here is the main reason bootleg grounds are dangerous. Suppose that the neutral wire becomes disconnected? Current will flow from the hot wire thru appliances and cause the neutral to become hot to ground. If your ground is really a neutral wire, everything that is grounded becomes hot also.
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