Modification of Old Electrical Work

For USA, Canada and countries running a 60 Hz supply service.

The short answer is yes, the center terminal is the ground wire, and the order of the two hot wires (red and black) does not matter, so long as you don't attach them to the same lug.

If you have a four wire plug in the wall, and are converting a 3 wire appliance, YOU NEED TO USE A FOUR WIRE CORD AND NEVER, EVER CONNECT THE GREEN AND WHITE TOGETHER ON THE CENTER LUG.

If your appliance is old enough, it will have only 3 connection terminals and no place for the ground wire to go. I repeat, DO NOT EVER just put the green ground wire on the center screw terminal, ESPECIALLY if you have a four wire outlet in the wall of your new home. If you do that you will just only be cheating yourself , your wife and anyone else in your house out of a great new safety feature.

What you need to do for an old appliance that has no place for a ground wire is this: you NEED to drill a small hole through the metal case on the dryer that will take a small nut and bolt, and you also need to sand off all of the paint around this nut and bolt so that it will get good contact with the metal case.

So, after you are done, stick the bolt through the hole, install a locknut and tighten it down as much as you possibly can.

Then, you can put the ground wire on the bolt, and install another locknut on top of the ground wire, and also tighten it down as much as you can.

This is the only proper way to upgrade an old appliance to 4 wire.

Also, on an old appliance, there should be a strap connecting the center terminal where the white neutral goes on your older appliance: this strap connects the neutral to the case of the appliance. YOU MUST remove it or cut it by any means necessary or you will just be stuck with a 4 wire upgraded appliance that still acts like a 3 wire. Never just connect the two green and white together if you have 4 wire.

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for USA, Canada and countries running a 60 Hz supply service

Short answer: yes and no. Some homes built during a certain period can.

Before a new code is adopted there is a lot of anticipation about newer code requirements, and new code requirements usually send manufacturers of products scrambling a year or two before to come up with products that meet the new requirements. But the government almost always allows them to sell off their old stock for a period.

If your home was built very late in 1994, to 1996, when the latest code was adopted, you may already have a 4 wire cable installed with a 3 prong outlet: the installers would just connect the ground to the outlet box or not at all and be done with it. So, in some limited cases, you just might be able to upgrade an outlet from 3 to 4 prong, and still be safe about it.

Otherwise, if the cable only has 3 wires in it, NO, NO, NO.

One exception to that rule: if you have got one of the one in a zillion homes where the builder cared enough to wire it with EMT (conduit). Then, to change anything at al is simple to do: you just run the fourth wire through it. Simple as that.

The reference to Neutral being ground is entirely INCORRECT. Neutral is NOT GROUND.

Wiring a home with EMT is NEVER done. I have been doing this kind of work for a very long time and have never seen or used EMT in a residential application. IN garages, yes, IN industrial environment- It is required but never in a residential situation.

The simplest answer to the original question is: If you presently have a three wire outlet, there would be no need to change to a 4 prong outlet unless some local requirement makes it necessary. The feed to the new outlet would have to be upgraded to a three conductor plus ground .

Other answers

It can BUT there is a reason why you shouldn't do this unless you are a Licensed Electrician: if the appliance NEEDS a four prong receptacle and you just change the receptacle without wiring it up correctly, it will probably be UNSAFE and will also void a) your home's fire insurance cover and b) the warranty of the appliance.

In my 30+ years of experience, a lot of people want to save money on the most dangerous energy source in their home.

It makes much more sense to call a Licensed Electrician and pay to have it done right.

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(LIFE SAFETY WARNING! [Disclaimer]

Electricity is dangerous!

You can be injured or killed!

Improper installations can cause fire, injury and death!

Should you be doing this yourself?)

1] No!

2] I take it you have a new stove or dryer

3] The old outlet is three prong

4] The new appliance is 4 prong.

5] You have 2 choices

6] Install a new supply cable to feed the appliance with a 4 prong outlet OR utilize the exception to grounding which is allowed in the NEC for existing circuits which lets you reconnect the chassis ground to the neutral [ground] third conductor and change the cord set to a three prong cord - check to make sure your township has not superceded these allowances - the "authority having jurisdiction" has the last say.

7] Secure appropriate permits.

8] Install the equipment according to standard practice in a workmanlike manner!

9] Secure underwriter's inspection! [For your peace of mind.]

or ... call a licensed electrician.

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This will vary by state. Turn off the power remove the old device. If there are 4 wires present then the device can be changed. If not your local inspector may be able to offer some alternatives.

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You may need to run new wire to your outlet. Older 3 wire plugs had two hots and a neutral, no dedicated ground. So there may not be a ground wire, or there may not be a neutral wire in the box. You need all four wires to safely wire that new outlet. The new outlet is safer (which is why they changed), so take the time to install it correctly.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

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Back to the original question, which was a new dryer being installed in a house with a three-prong dryer outlet.

Your three-prong cord has two thick wires and a thin one. The thin one, which is in the middle, is neutral not ground. When you remove the cover plate over the electrical connections on the new dryer you'll find a terminal block with three screws, and a green screw for ground a couple inches away. Leave the green screw alone; do not connect anything to it because this cord has no ground. The middle wire goes to the middle screw on the terminal block. The two thick wires go to the other two screws, and it doesn't matter which thick wire goes on which screw so long as you don't hook them to the same screw. (Yes, I've seen it. No, it didn't work.)

Now! If you call an electrician and get this outlet changed to four-wire service (which will either be Not Cheap if the electrician can find a ground in your laundry room or Extremely Expensive if he's got to pull wire), the new cord will have red, black, green and white wires coming out of it. Green is Ground, and goes to that green screw you ignored with your three-wire cord. White is neutral (middle screw) and the red and black wires, which are hot, go to the two outside screws.

Now, I assume that you want to keep the outlet "switched" (switched means the outlet is hot only when the switch is turned on). If you want to make it "unswitched" (i.e., hot all the time), things get complicated. I also assume that your switch is just a regular on/off switch, and not a three-way switch (with a three-way switch, you can turn the device on and off from two different locations). If either of these assumptions is untrue, stop right here - the following instructions will not work for your situation.

The first thing you need to do is identify the circuit that runs to this switch/outlet combination. Plug a night-light or small lamp into the switched outlet and turn it on at the switch and at the light. Then go to your breaker box. The individual breakers may be labeled in such way that you can immediately identify which breaker is for that circuit, or at least narrow it down a little bit. Otherwise, just start flipping any switches that seem likely (one at a time) off and on until your night-light goes out (unless your breaker box and the outlet are within sight of each other, you will need an assistant to tell you when the light goes off). Once you have identified the breaker that supplies power to this switch/outlet combination, mark it with a piece of tape, but for now, turn the breaker back on.

(It may be helpful at this point to identify any other devices that are on this circuit.)

Okay, now you need to find the circuit wires that supply this switched outlet. Chances are, you won't be able to follow the wires all the way from the breaker box to the switch and then to the outlet, because the wires are hidden behind walls, and you don't want to tear down your walls. But, if the wires run through your attic, you can still figure out which ones go where. You will need a circuit tester capable of detecting current through both insulation and sheathing.

Go up to your attic and look around for any electrical cables. A cable is a bundle of individual wires, wrapped in a plastic sheath. They may not be easily visible, but nailed to the sides of your ceiling joists and buried under home insulation. If you find such cables, that's a good sign - it means that the person who wired your house used the attic for running electrical cable. If you don't find any in the attic, he may have run the cable through the walls, and it's going to be a real pain in the butt to do this.

Once you have established that there are electrical cables in the attic, you need to identify which ones are part of your circuit. First go to the area of your attic that is directly above your switch. This is not an easy thing to do because you can't see the switch from the attic. But as long as you have a decent sense of direction and distance, you should at least be able to narrow it down to a small area. Start searching that area for electrical cables. What you are looking for is a cable coming up through a hole drilled through the top plate of a wall (a top plate is a 2x4 that stretches horizontally across the top of a wall, perpendicular to the studs). If you find such a cable, and you are in the right area, there's a good chance that this cable is coming from or going to your switch. There may be two cables coming out of that hole. If so, one is going to the switch and one is coming from it. But first we need to make sure that it is somehow connected to that switch.

Now you really need an assistant. With the breaker still on, and the wall switch on, check the cable for current with your circuit tester. If you have no current, then either your circuit tester isn't working, you're not using it right, or the cable is not connected to any active breaker. Check your circuit tester against another cable. If it still isn't working, you need to take it back to the store and get one that will. If possible, have someone show you how to use it.

Once you are satisfied that your circuit tester is working properly, check the cables again. First, you want to find a cable that has current. Then have your assistant turn the breaker off. If you no longer have a current, you know you are on the correct circuit. But, as mentioned before, there are likely two cables coming from this same hole in the top plate, one going to the switch and one coming from the switch, and you want the one coming from the switch. Of these two, the one that is heading in the direction of the outlet is most likely the one you want. But to check that, have your assistant turn the breaker back on (at which point, you will have a current again), and then turn the wall switch off. If you no longer have a current, this is the cable you want. Basically, the section of cable you are looking for will have current if and only if both the breaker and the wall switch are turned on. If either is turned off, there will be no current. (Note, if there is only one cable coming from this hole in the top plate, that is fine, as long as you can identify it as the one that is coming from the switch.)

Okay, so now you have identified the cable that is coming from the wall switch. It probably runs along the top plate of the wall to a location directly above the switched outlet, then runs down through a hole in the top plate to that outlet. You are going to splice this section of cable, somewhere in between the switch and the outlet. But don't cut anything yet. Look closely at the cable. Every 3-4 feet, there should be printing on the outside of the cable that tells you what kind of cable it is. If the cable is stapled down to the top plate, you may have to pry up some staples to look at the underside. What you are looking for is two numbers, separated by a dash. It may say 12-2 or 14-3 or something like that. The first number is the gauge of the individual wires (like the "gauge" on a shotgun, a smaller number means bigger, so 12-gauge wire is bigger than 14-gauge). The second number tells you how many wires (not counting the ground wire) are in the cable. (If the second number is a 3, stop here. You have a more complicated installation and the remainder of these instructions will not work.) The new cable you purchase should match the cable that is already in place. Most building codes require using 12-gauge or lower (lower gauge = bigger wire) wire. If your current wiring is 14-gauge, it may not meet the local building code, and even if it does, there is a potential fire hazard. But there's nothing you can do about that short of hiring an electrician to re-wire your whole house (and then another professional to repair all the walls that the electrician tears up).

So now you know what kind of cable you need. But how much do you need? On the section of cable that you are going to splice, find the point of that section that is located closest to the spot where you want to install your ceiling fan. With a tape measure, measure from that point to the spot where you want the fan. Measure along ceiling joists or top plates where possible, and, where that's not possible, measure in a line perpendicular to the joists (no diagonal lines). When you have the distance measured, double that distance, then add 5 feet. That's how much cable you will need. You can buy the cable by the foot in some stores, but it is generally cheaper (by the foot) to buy it by the box. Boxes come in multiples of 25 feet. Hopefully you won't need more than 25 feet. I would say forget about buying it by the foot and just buy a 25-ft box. That way, if you mess up, you have some extra cable to play with.

While you're at the hardware store, there are a few other things you will need. You will need two 2x4-inch electrical boxes, with "blank" cover plates and screws. By "blank" cover plates, I mean solid plates with no holes for switches or outlets. These boxes will be used for your splices and will not have any external controls or devices, so you want them completely sealed. I would recommend the plastic boxes with nails for attaching to studs or joists. They are less than a dollar apiece in most hardware stores, sometimes as cheap as a quarter. You will also need a box for mounting your ceiling fan. There are wide variety that can be used. If you want to mount your fan directly on a ceiling joist, there's a circular box that has a back side that is indented to fit around the underside of a joist. If you are mounting the fan between two joists, you can get a circular box that is mounted on a telescoping metal brace that can be nailed at both ends to two neighboring joists. But I don't think those things provide enough support for a spinning ceiling fan. What I would do in this case is just buy a standard plastic round box and cut a piece of 2x4 lumber to fit between two joists (later, after you cut your hole in the ceiling, you will nail your box to the 2x4 and nail the 2x4 to the two joists).

In addition to your three electrical boxes, you will need an assortment of wire nuts. Most of your connections will involve two wires coming from cables (even if they are 14-gauge, they will be bigger than the wires that go to the ceiling fan, which you don't really have to count). Now, "standard" wire nuts are color coded to indicate how many wires of different sizes they can hold. The yellow wire nuts, if standard, can easily accommodate two 12-gauge or 14-gauge wires (as well as the little wires from the ceiling fan) So make sure you have plenty (at least 10) of the standard yellow wire nuts. I would also get 2-3 red wire nuts, just in case, as well as 2-3 orange nuts and 2-3 grey nuts. Your best bet is to just buy an assortment pack, provided it contains plenty of yellow nuts.

You will also need some electrical tape - one roll should be plenty. And if you don't already have a pair of wire cutters, buy one. Get the needle-nose kind that doubles as a pair of pliers. And some cable staples (U-shaped nails, with points on both ends). And, if you don't already have one, a utility knife for cutting the tape and the cable sheathing. And both a flat-head and Phillips-head screwdriver, but I assume you already have those. Oh, and a pair of bolt-cutters would come in handy, but you can make do without it, so don't buy a pair just for this project. That's all I can think of for now.

Okay, you're back at home now with all of your supplies. Before you start doing any work, turn the breaker off. Now, go back to the attic, with all of your tools and supplies, and locate the section of cable you are going to splice. At this point, you need to notice whether the cable is running parallel to or perpendicular to your ceiling joists. If the cable is parallel to the joists, mark the point at which the cable comes closest to the ceiling fan (the point you measured from when you were trying to find out how much cable you needed). Then determine which direction the switch is from this point, and move 6-8 inches away from the switch and cut your cable right there. A pair of bolt cutters will cleanly slice through the entire cable, but if you don't have bolt cutters, you can still cut it. With a utility knife extended just to the first stop, carefully slice through the sheathing of the cable, parallel to the cable, for a distance of about 2 inches on either side of the spot where you want to cut the cable. Peel back the sheathing and hold it away from the wires inside and cut through the sheathing. Then separate the wires inside the sheath and cut them individually with your wire cutters. When the cable is cut, place a mark on the sheathing 6-8 inches from both cut ends (one of the wires will already have such a mark).

If the cable is perpendicular to the joists, you want to cut it somewhere in between the two joists, as close as possible to where your ceiling fan will be located. The cut doesn't have to be exactly in the middle of the two joists, but you should have at least 6-8 inches between the joist and the cable end, on both sides, to work with.

Now you need to install your two "splice" boxes. If the cable is parallel to the joists, you will mount the boxes on the same top plate that the cable is running across, or, if one is available, an adjacent joist. To find the exact location to mount the box, punch out one of the holes in the back side of the box and slide the marked end of the cable into that hole, pull it tight, and slide the box up the cable until the mark is visible inside the box. You should have at least 6 inches of the cable inside the box or protruding out the open end. Using the nails attached to the box, secure it to the top plate or to the joist. If securing to the top plate, you will have to turn the box sideways so that the opening is facing horizontally, toward the ceiling fan. The open face of the box should extend slightly out over the edge of the top plate so that you can attach the cover plate to the box securely with no interference from the top plate. If securing to the joist, the opening will be facing up. The open face of the box should extend above the top of the joist so that you can attach the cover plate to the box securely with no interference from the joist. Whether mounted on a joist or a top plate, the long side of the box will be parallel to the original direction along which the cable was running. For your other splice box, slide the other cut end of you cable into your other box and slide the box down the cable until you have 6-8 inches of cable inside the box or protruding out the open face. Secure this box to the top plate or joist the same as you did the other box. Then, for both boxes, use staple nails to secure the cable to the top plate or joist just before it enters the small holes on the back sides of the boxes.

If your cable is perpendicular to the joists, your boxes will be mounted on the two neighboring joists, with both of them between the joists, and as close to the top plate as possible. Nail your two boxes in position with the opening facing up. The open end of the box should extend above the joists slightly so you will be able to attach the cover plate securely with no interference from the joists. Push the two cable ends through the small holes in the back of their respective boxes and pull them tight through the opening of the box. Use staple nails to secure the cables to the joists just before they enter the back of the box.

Now, you want to peel back the sheathing from the cables that are protruding from your two boxes. Use a utility knife to slice the sheath as far as you can inside the box, being careful not to cut the insulation around the individual wires inside the sheath. Peel back the sliced sheathing and cut it off. You may also find some paper strips inside the sheath - cut that off too.

Now install the box for your ceiling fan. Cut a hole in the drywall ceiling just big enough to accommodate your box (you may want to cut this hole from below, so you know how it's going to look in your living room or bedroom, but you don't want it to be on a stud, so there is some degree of coordinating the hole cutting between both the attic and the down-stairs). Slide the open end of the box down through the hole in the ceiling until the opening is about halfway through the drywall. Hold it in place and set your 2x4 support on top of it, butting against the two joists. with a pencil, mark the edges of the box on the underside of the 2x4. Pull everything out and re-align the back side of your box to the marks on the 2x4 and attach it there with wood screws. Then slide the box back into the ceiling hole (from above), again to the point where the open end is about halfway through the drywall. The ends of your 2x4 should be butting up against the inside edges of your two joists. Put two nails through the other side of each joist and into the ends of your 2x4, securing it, and the box, tightly in place.

Now you get to use your new cable. Take the end of your new cable and insert it into one of the holes in the back side of one of your splice boxes (not the same hole that the other cable is going through). Pull it through the open side until you have 6-8 inches of cable inside the box or protruding through the open side. Secure the cable to the joist with a cable staple just before it enters the box. Now unroll the new cable in the direction of your ceiling fan box. Run it along the joist until it is even with the fan box. Pull the cable tight and secure it to the joist with a staple nail at that point. Then bend the cable in the direction of the ceiling fan box and stretch it about a foot past the leading edge of the box and cut it there. Push the cut end of the cable through one of the small holes in the back side of the box, as far as it will go. Then secure the cable to the underside of the support 2x4 as close as you can to where it enters the back side of the box. Repeat this procedure with another length of cable going from the other splice box to your ceiling fan box. Then go back along both of your new lengths of cable and secure them to the joists every 2-4 feet with cable staples.

Now go back to your two splice boxes and strip the sheathing off of the cables that are going to the ceiling fan box, the same way you did the other cables coming into those boxes.

Now you are finally ready to start connecting wires. First the splice boxes. The procedure is identical for both splice boxes so I will tell you only once. Match the wires up by color. You should have two each, black, white, and bare. (You shouldn't have any red wires - if you do, the second number on your wire type would have been a 3, and you should have stopped long ago.) Using a pair of wire strippers, strip the insulation off the last 1/2 to 3/4 inch of both black and both white wires. (If you don't have wire strippers, you can use a pocket knife to carefully cut through the insulation all the way around the wire, then pull off the insulation with pliers.) Using your pliers, twist the two black wires together in a clockwise direction. Squeeze the two tips of the wires together as tightly as possible. Slide the open end of a yellow wire nut over the twisted-together wire ends, push it tightly against the wires, and turn it clockwise as far as you can (use your pliers if you need to, but be carefully not to break the wire nut). Hold the wire nut in one hand and tug hard on each of the two wires separately with the other hand to make sure both are securely fastened inside the nut. There should be no un-insulated wire visible outside of the nut - if there is, you stripped too much insulation off. Then wrap electrical tape around the wires and the nut. (When wrapping connections with electrical tape, I like to fold the last half inch or so of the tape over onto itself so it doesn't stick to the connection. That way, if I have to go back and undo everything, I have a little "tab" I can pull to remove the tape. Otherwise, I would end up having to cut the tape off.) Repeat this procedure for the two white wires. Then repeat again for the two bare wires, except, since these two wires are entirely bare, you will have some un-insulated wire outside of the nut. Bend and/or fold all the wires inside the box until they are no longer protruding from the open face. Put your cover plate in place over the open face and secure it to the rim of the box with the screws provided.

Once you've done this for both splice boxes, you are ready go back downstairs and prepare your ceiling fan box. Strip the sheathing off of both cables as far as you can and cut off the excess. Then cut the ends of the individual black, white, and bare wires to 6-8 inches. Then, using wire strippers, strip the insulation from the last 1/2 to 3/4 inch of the white and black wires.

Now you are ready to attach the ceiling fan. Your ceiling fan should have come with instructions for installing it, and I don't want to contradict anything they say. However, I will tell you that ceiling fan instructions often assume that your fan will be installed at the end of a circuit, and therefore that you will have only one set of supply lines to deal with. But because you are installing this fan in the middle of a circuit, you will have two supply lines to deal with (one incoming and one outgoing). All this means is that, where your instructions say to connect the (one) black, white, or bare supply wire to something, you will actually have two supply lines to connect. Just twist them both together with whatever other wires are supposed to be connected. However, you may have to use a bigger wire nut than the ones that came with your fan, because you have more wires to connect. (That's why I recommended that you buy plenty of the yellow wire nuts.) Other than that, install your ceiling fan according to the instructions that came with it.

After everything is connected, go back to the breaker box and turn the breaker back on. Go back to the room where your celing fan is located and turn on the switch. If the ceiling fan doesn't come on, pull the chain. (If it still doesn't come on, you messed up somewhere.) If your ceiling fan has a light attachment, test it too. Finally, test the outlet and make sure that it works (it should only work when the switch is on).<><><>

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

If you do this work yourself, always turn off the power

at the breaker box/fuse panel BEFORE you attempt to do any work AND

always use an electrician's test meter having metal-tipped probes

(not a simple proximity voltage indicator)

to insure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.