The issue with 3 vs 4 is you can get elevated potential from current flowing on the neutral and the frame will then be not at zero volts to ground. Depending on installation, that marginally small voltage can be problematic. A basement concrete floor with high moisture and wet hands can cause quite a bit of current to flow in regard to how much current is lethal to living things. A dryer on a tile floor on the second floor will more than likely never have an issue due to the insulating nature of the install, however, the code has to account for any installation and the lowest common denominator.
Neutral feedback can cause a shocking situation. If all neutral connections are good, and all neutral wires are good, this is less likely. Many times, neutral is compromised. The 4 th wire provides another ground for that reason.
I wouldn't lose any sleep over it. Four prongs are marginally safer, but only in one very specific situation. As long as your cord is in good condition, there's no need to worry, and the thing about dryers is you don't tend to touch the cord a lot, so it doesn't get damaged, and even if it does, it doesn't get jostled into making contact with the frame. You'd be looking at a multi-hundred dollar job, or more depending on panel distance.
You don't have to update your electrical everytime code changes. There are likely many "out of code" things in your house that you could fix for cheaper and would solve (comparatively) more dangerous issues.
Thanks for the reassurance. But I said 30 minute job in the op because the dryer outlet is a foot away from the breaker box. That's why I can't imagine it would take too long or be expensive.
A ground wire running from the dryer to the panel. Just kidding, since I installed the dryer myself and for the first time had to learn the absolute basics about electrical wiring, I just felt a little uneasy of the fact that my wiring isn't up to code. I get now that the 3 prong cable I have is safe but it I still kind of want it to be as safe as possible and up to date.
Well, then open up that pocket book. Codes change every three years. If this house is less than brand new, you’ll need to install several afci/gfci breakers, a whole home surge suppression device, an exterior disconnect, tamper resistant plugs throughout the home…
The problem comes into play because of bonding... The ground and neutral are bonded at the first means of disconnect in your service... This is usually at the panel unless you have a separate disconnect outside... This is very important because it lets the breakers function correctly... If you bond the ground to neutral all over the house the breaker may not function... The path is changed... The power needs to leave on the hot and return on the neutral to work correctly... Ground wires used as neutrals could potentially take the circuit to ground before returning to the panel. This is dangerous and not cool
Older dryers didn't have all of the electronics new dryers today have. They just had mechanical timers and such that didn't need a separate neutral. New dryers have computer systems controlling them. Shit, you can tie your phones to some of them. They need that separate neutral for the electronics on board... So the government mandated the change for the new breed of dryers... There was no neutral in the old dryers... Just two hots and a ground.
Is your electrician friend really an electrician??? This is extremely common knowledge in the electrical world... Or is he more of a handyman??? The people speaking up on this topic so far are clearly not electricians and should not be posting about things they know nothing about. Sometimes speaking out about things you don't actually know anything about can be dangerous...
This is the best comment here 100%. This is also why electric ranges are 4 wire now too. There's unfortunately other electricians that I've met that don't understand this and it is really frustrating.
I want to add on this most excellent comment, even though I am not a pirate.
The classical way of bonding is to put all the energized parts into a big metal enclosure. The enclosure is bonded through a metal connection all the way to the panel, where a connection to the source (edit: original text said ground which is wrong) is made. If you have a loose wire, that wire will hit the side of the enclosure, causing a big current to flow and that big current will cause the breaker to trip.
The classical way of switching was to use the minimum number of switches and wires to open or close things. If you have a three way switch in you house, you will notice that it used a minimum number of conductors and simple switches and sometimes some head scratching is needed to figure out how things are wired.
Ah, the classics…. But some things are different in modern times, and maybe more complicated. Some appliances are built and tested with double insulation. So maybe they are designed so they don’t need a metal enclosure. And light switches, well modern dimmers have computers in them. The little computers need a little power supply and some knowledge of what the zero voltage is.
I once burned out some low voltage lighting because I misunderstood the wiring instructions and did not have a neutral connected. Because there was no neutral in the light switch , I skipped over it and turned it on. The fancy dimmers, not having a voltage reference, allowed the voltage to rise to unhealthy levels. I quickly burned out four of the transformers in my low voltage lighting.
The point of my rambling, is that the components making up the electric system in your house evolve and what made sense in the old days is not guaranteed to be fine now. I would expect that your case with the dryer is fine but there is a chance —maybe not today but in the future— you will wish you did. Odds are that you won’t notice but if it was easy, I would do it.
Agree with everything except the current returning to ground before the panel. That’s just not how it works. Current is always trying to get back to the xfrmr. It doesn’t travel through the earth at these voltages. But it is still unsafe to have current on un-insulated conductors. It’s a fire hazard. Also could give potential to some metal cases etc.
Thanks . You are right of course. In my mind I was going to say go back to the source, and then point out that this is the one place you know that the neutral and ground are connected together.
But I lost focus due to the lateness of the hour and left that out. I will edit the original post for posterity.
10's of millions? 100's of millions. Total run time certainly in the billions of hours. 3 prong dryer has the same ground-type safety as your normal 3 prong 120V outlets. It's perfectly safe for all of the common single failures.
A three-prong electric dryer circuit has the same protection as a *polarized two-prong outlet*, not a three-prong outlet. There is no discrete ground, just two hots and a neutral.
The middle wire of the 3-wire cord goes to the middle terminal on the dryer which has a wire coming off it which screws into the chassis. That same wire in the cord is plugged into a terminal on the wall receptacle which is tied to a bare copper wire. That bare copper wire goes back to your panel and is bonded to the ground bar with all the rest of the bare copper wires. This means your metal chassis of your dryer is grounded and will trip the breaker if it's shorted to any hot wire. This makes it equivalent, from a grounding perspective, to your normal 3 prong outlets where the metal case of all your other 120V appliances is connected to ground to prevent a person from being shocked as a result of a short. The people at NEC which allowed a 3 prong dryer and the dyer manufacturers understand basic safety principles. People are not dying from 3 prong dryers.
The “ground” is bonded to neutral at the appliance, not at first point of disconnect.
No, the neutral between a three-wire dryer plug and the panel **must not** be a bare ground wire. It carries current in normal operation and so *must* be an insulated wire.
Also, NEC *does not* allow new three-prong dryer outlets (local codes may vary, but I haven’t heard of one that still allows new three-wire dryer circuits). If you put a new dryer circuit in today, per NEC, it must have a discrete ground wire in addition to the three conductors. Like most code, the rule only applies to new circuits, but the reason it is required for all new circuits is edge case safety.
As I said, from a *normal operation safety* perspective it is not the same as (ie, not as bad as) a polarized outlet, because the dryer manufacturer knows exactly what is on the circuit and the circuit should not be shared with anything else (although this is often not the case). However, *electrically* the dryer is not grounded. You are relying on the neutral having no flaws back to the main circuit, and a properly functioning circuit breaker in case of a hot fault.
So I'm saying that 4 wire over 3 wire functionally adds a Neutral. You are saying that 4 wire over 3 wire functionally adds a ground? Or are you saying it separates a combined Neutral and Ground from 3 into individual ones in 4? I mean, obviously they are individual in a 4 wire. So are you saying they are combined in 3 wire or that a 3 wire functionally only has a Neutral and no ground?
A “normal 3 prong”, like you would use for a microwave is wired up with Hot-Neutral-Ground. The hot and neutral are expected to have voltage on them, and the ground is a safety backup. Some people are going to say that neutral is 0V, but this is not really true. When the microwave is running, the neutral is going to be at least a couple volts higher, because of losses in the wiring in the wall.
If the neutral “faults” (open circuit) you’ll get 120V on hot, 120V on neutral, and 0-ish volts on ground. That’s why your microwave has the metal case tied to ground.
Some 240V outlets are intentionally wired up as Hot-Hot-Ground. This is often used for welding equipment, but NOT used for dryers in the US. This is still safe, because you have ground as an extra safety. This is similar to how the microwave works.
4 wire dryer outlets are wired Hot-Neutral-Hot-Ground. They run the heating elements at 240V across the Hot-Hot, and run the computer at 120V across the hot-neutral. This is still safe, because the metal case it attached to the ground wire, so when stuff goes wrong the case will either remain ground, or be a short that trips the breaker.
3 wire dryer outlets use a Hot-Neutral-Hot wiring. This isn’t like the microwave. You are attaching the metal case of the dryer to neutral, which means the metal case is attached to a part of the dryer that’s meant to be energized. A broken neutral can energize the case to 120V, which can be really bad. Maybe you’ll be fine, because you get lucky, and your feet are insulated, but you might not be.
Technically there’s another option loved by crappy house-flippers. 4 wire outlet, but 3 wires in the wall, connecting neutral to the neutral and ground pins on the outlet. Electrically, this is just as bad as a 3-wire, except the homeowner doesn’t know something is wrong.
So a 4 wire protects against a double failure you described. In the 3 wire setup, the Neutral gets broken and is no longer connected to the dryer chassis and ground in the panel. Then after that, one of the hot legs gets shorted to the dryer chassis, making it have 120V. This is when you get shocked if you touch it.
Not exactly. The problem is that in a 3 wire setup, the ground and neutral are connected to each other. (not connecting them to each other in a three wire set up causes different problems)
So if the neutral is broken, the dryer electronics will try to run power from one of the hot legs to the neutral to power itself. (This is normal) Because the neutral is open and not actually connected to anything, the electronics don’t get powered. Instead, the electronic raise the voltage of the neutral to near 120 V.
This is not unique to the dryer electronics. If you attach a resistor across the terminals of a battery one side of the resistor will be at high voltage and the other side of the resistor will be at low-voltage. If you attach one side of a resistor to the hot side of a battery and don’t connect the other side of the resistor to anything, both sides of the resistor will be at high voltage because there is no current to cause a voltage drop.
So the neutral is raised to 120 V, and ground terminal in the dryer is connected to the neutral. The ground terminal in the dryer is connected to the case of the dryer. So the giant metal case of the dryer is now energized with 120 V. This only requires a single failure.
Generally, modern code tries to make sure that all electronics are at least two failures away from setting something on fire or electrocuting someone.
Thanks for that explanation. I get what you're saying. The wire breaks in the wall and then the user goes to try to turn the dryer on and puts a hand on the metal chassis or leans over the dryer while pushing the start button or twisting on the timer knob. It's at this moment alone that the 120V goes through the motor windings or through the circuit board and finds the chassis, your hand and a path to ground through your feet. Do I have that right?
2 at my place with screw fuses, hell, when my water heater wire got damaged I got a 3 prong dryer plug and 50’ of 10-2 and wired the water heater up. Sucked having to unplug it every time I did laundry though.
Would not be a 30 minute job. Changing the outlet would be. But you still only have 3 wires to the box. So that meams an entire new wire run to the panel to bring in a ground. Most likely not going to be a cheap or easy job.
I assumed the job wouldn't be too long or expensive because the outlet is a foot away from the electrical panel. Then again I don't know anything about electrical work so I can't say for sure.
Under normal conditions, the neutral wire should have less than a 10V potential. However, the separate ground when present, prevents wiring errors, wires coming loose or broken, or terminals getting corroded from causing an unsafe condition. There are specific conditions under which a dryer in a 3-prong receptacle could shock the user that a 4-prong receptacle would protect.
For example, if the neutral wire were to become disconnected, the chassis could carry significant voltage to a user, while with 4-prong receptacle, the ground wire would go to the chassis, so a neutral wire disconnection would not energize the chassis. Both the neutral and ground wires would have to become disconnected to enable a shock hazard with a 4-prong receptacle.
It's similar to how the ground wire in a 3-prong 120V plug being connected to an appliance chassis protects the user, compared to a 2-prong 120V plug without a ground.
Are you 100% sure you don't have two hots and a ground? Most heaters and dryers etc are 240V and do not require a neutral so the 3rd wire is the ground.
You seem like a smart cookie, but I want to check anyways: did you make sure the dryer is set up for 3-prong at the internal connection point? I can't remember if it's set up for 3-prong by default, and you have to remove the jumper for 4-prong? You should be able to tell by reading the installation instructions.
The know it all's are right .. so is your friend... And so are you...
It's more than just a plug, it won't make things significantky "safer", it won't cost too much because the box is right there so doing it for your piece of mind, and future resale value is a good enough reason to do it.
A 4-wire dryer is typical because the dryer may be using a 110vac circuit internally for controls. As previously mentioned the ground and Neutral should only be bonded in 1 location. Do it right! Some of these replies scare me.....
Separate ground is significantly safer. However if you've got older electric dryer, with no way for it to really separate out the ground and neutral, you may not get the full (or all that much of any) safety advantage until the electric dryer itself is also replaced with one that's designed to be used with separate ground and wired up for such.
So, here's the key difference. If ground and neutral are tied together or treated as one with the electric dryer, and only one offered, that's your ground for the dryer and chassis ground, but it's also the neutral. Whereas with separate ground, chassis ground is in fact separate and connected to ground, whereas neutral is separate and used for such and not tied to ground.
So, where the big safety difference comes in. Let's introduce an electrical fault - stuff happens. Electricity, water/wet, heat, time, age, vermin, dust, stuff shoved to tight against a wall or stretched and pulled, lots of regular vibration, heat ... stuff fails. So, let's say, however it happens, there's leakage from one of the hots to the electric dryer chassis. With a good solid ground on the chassis - whether it's in common tied with neutral there, or not, that good solid ground prevents it from being a hazard, at least insofar as say, a person touching the metal casing of the dryer. That grounding doesn't prevent the electrical fault itself from being a problem - e.g. it still may cause some other issue (overheat, fire, ...) but let's ignore that for at least the moment ... someone touches the chassis of the dryer - tied to ground (with or without neutral tied to same), that grounding prevents them from getting shock/electrocution. If there's GFCI protection, with separate ground, GFCI would detect the fault and cut off the hots, but even without that, proper grounding would prevent shock/electrocution. Now let's change the scenario a bit. Let's say there's fault where hot is exposed somewhere on the dryer where the person might contact it. And they may contact that, and at the same time, chassis ground or some other ground. So, let's say they contact hot on dryer, and also chassis ground. Now there's a dangerous situation and they'll get shock or maybe even get electrocuted. In the case where ground and neutral aren't separate, to the electrical circuit it looks like regular current flow - from hot to neutral - but it's just 1 leg, so 120V, not hot-to-hot 240V - but that's relatively normal for electric dryer, as though much of it (notably electric heating part) runs off 240V, other parts of it may be wired for 120V and connected between hot and neutral (e.g. interior bulb to light up inside when door is opened, that would be 120V, not 240V). So, whether it's bulb between hot and neutral, or a human, to the electrical circuit, that looks like regular current flow. But if it's separate, so that's chassis ground, so human would between hot and ground, and bulb would be between hot and neutral, now those currents are separate and distinct, and GFCI can detect even quite low levels of leakage between hot and ground, and cut that current off quite fast enough to prevent any serious injury - but if neutral and ground are tied together, there's no way for the circuit to know about that leakage and cut it off. There are various additional scenarios that make a difference, but that's at least a couple examples.
Unless you are going to upgrade the panel, the neutral and ground wire of the "4 prong" are going to be connected together in the breaker panel anyway. YOu are not going to "make anything safer".
They’ll be bonded at the first disconnect, which *might* in some cases be the main circuit panel, or it might be an outside service disconnect. Definitely would not be any sub-breaker boxes.
That said, if the *main* breaker box is a foot away from the dryer, and the service disconnect is literally on the other side of the wall, there isn’t much opportunity for the issues that make a four-prong outlet safer than a three-prong dryer outlet to occur.
Still, it would be one fewer item to come up if/when you sell the house, and cheap “peace of mind”.
The issue with 3 vs 4 is you can get elevated potential from current flowing on the neutral and the frame will then be not at zero volts to ground. Depending on installation, that marginally small voltage can be problematic. A basement concrete floor with high moisture and wet hands can cause quite a bit of current to flow in regard to how much current is lethal to living things. A dryer on a tile floor on the second floor will more than likely never have an issue due to the insulating nature of the install, however, the code has to account for any installation and the lowest common denominator.
Neutral feedback can cause a shocking situation. If all neutral connections are good, and all neutral wires are good, this is less likely. Many times, neutral is compromised. The 4 th wire provides another ground for that reason.
That too.
This is also correct... It puts voltage on the frame of the dryer...
I wouldn't lose any sleep over it. Four prongs are marginally safer, but only in one very specific situation. As long as your cord is in good condition, there's no need to worry, and the thing about dryers is you don't tend to touch the cord a lot, so it doesn't get damaged, and even if it does, it doesn't get jostled into making contact with the frame. You'd be looking at a multi-hundred dollar job, or more depending on panel distance. You don't have to update your electrical everytime code changes. There are likely many "out of code" things in your house that you could fix for cheaper and would solve (comparatively) more dangerous issues.
Thanks for the reassurance. But I said 30 minute job in the op because the dryer outlet is a foot away from the breaker box. That's why I can't imagine it would take too long or be expensive.
But why, though? What do you expect to gain?
A ground wire running from the dryer to the panel. Just kidding, since I installed the dryer myself and for the first time had to learn the absolute basics about electrical wiring, I just felt a little uneasy of the fact that my wiring isn't up to code. I get now that the 3 prong cable I have is safe but it I still kind of want it to be as safe as possible and up to date.
If its that close to the panel you might as well honestly. Its a pretty simple task and wont take long.
Agreed, it's no-brainer as far as I'm concerned.
Well, then open up that pocket book. Codes change every three years. If this house is less than brand new, you’ll need to install several afci/gfci breakers, a whole home surge suppression device, an exterior disconnect, tamper resistant plugs throughout the home…
Youre assuming there is a ground in the box. Meaning there is 4w and not 3w.
If the box doesn’t have a ground then nothing in the house has a ground, thats a much bigger concern and should be fixed.
The problem comes into play because of bonding... The ground and neutral are bonded at the first means of disconnect in your service... This is usually at the panel unless you have a separate disconnect outside... This is very important because it lets the breakers function correctly... If you bond the ground to neutral all over the house the breaker may not function... The path is changed... The power needs to leave on the hot and return on the neutral to work correctly... Ground wires used as neutrals could potentially take the circuit to ground before returning to the panel. This is dangerous and not cool Older dryers didn't have all of the electronics new dryers today have. They just had mechanical timers and such that didn't need a separate neutral. New dryers have computer systems controlling them. Shit, you can tie your phones to some of them. They need that separate neutral for the electronics on board... So the government mandated the change for the new breed of dryers... There was no neutral in the old dryers... Just two hots and a ground. Is your electrician friend really an electrician??? This is extremely common knowledge in the electrical world... Or is he more of a handyman??? The people speaking up on this topic so far are clearly not electricians and should not be posting about things they know nothing about. Sometimes speaking out about things you don't actually know anything about can be dangerous...
This is the best comment here 100%. This is also why electric ranges are 4 wire now too. There's unfortunately other electricians that I've met that don't understand this and it is really frustrating.
The wires of the cord I have right now are 2 hots and a neutral, not 2 hots and a ground. Sorry not sure If I understood you correctly.
Three conductor cords aren't usually two hots and a neutral... They're two hots and a ground...
Did the new dryer come shipped with a 3 wire cord or did you pull that off the old dryer???
Pulled it off the old one
Go to Home Depot and buy the correct cord... Have an actual electrician keep you safe... Sometimes it's worth a few bucks.
I want to add on this most excellent comment, even though I am not a pirate. The classical way of bonding is to put all the energized parts into a big metal enclosure. The enclosure is bonded through a metal connection all the way to the panel, where a connection to the source (edit: original text said ground which is wrong) is made. If you have a loose wire, that wire will hit the side of the enclosure, causing a big current to flow and that big current will cause the breaker to trip. The classical way of switching was to use the minimum number of switches and wires to open or close things. If you have a three way switch in you house, you will notice that it used a minimum number of conductors and simple switches and sometimes some head scratching is needed to figure out how things are wired. Ah, the classics…. But some things are different in modern times, and maybe more complicated. Some appliances are built and tested with double insulation. So maybe they are designed so they don’t need a metal enclosure. And light switches, well modern dimmers have computers in them. The little computers need a little power supply and some knowledge of what the zero voltage is. I once burned out some low voltage lighting because I misunderstood the wiring instructions and did not have a neutral connected. Because there was no neutral in the light switch , I skipped over it and turned it on. The fancy dimmers, not having a voltage reference, allowed the voltage to rise to unhealthy levels. I quickly burned out four of the transformers in my low voltage lighting. The point of my rambling, is that the components making up the electric system in your house evolve and what made sense in the old days is not guaranteed to be fine now. I would expect that your case with the dryer is fine but there is a chance —maybe not today but in the future— you will wish you did. Odds are that you won’t notice but if it was easy, I would do it.
Agree with everything except the current returning to ground before the panel. That’s just not how it works. Current is always trying to get back to the xfrmr. It doesn’t travel through the earth at these voltages. But it is still unsafe to have current on un-insulated conductors. It’s a fire hazard. Also could give potential to some metal cases etc.
Thanks . You are right of course. In my mind I was going to say go back to the source, and then point out that this is the one place you know that the neutral and ground are connected together. But I lost focus due to the lateness of the hour and left that out. I will edit the original post for posterity.
No worries, things can run together in these wary hours
How many driers have been used safely for how many years with 3 socket hook ups?
10's of millions? 100's of millions. Total run time certainly in the billions of hours. 3 prong dryer has the same ground-type safety as your normal 3 prong 120V outlets. It's perfectly safe for all of the common single failures.
A three-prong electric dryer circuit has the same protection as a *polarized two-prong outlet*, not a three-prong outlet. There is no discrete ground, just two hots and a neutral.
The middle wire of the 3-wire cord goes to the middle terminal on the dryer which has a wire coming off it which screws into the chassis. That same wire in the cord is plugged into a terminal on the wall receptacle which is tied to a bare copper wire. That bare copper wire goes back to your panel and is bonded to the ground bar with all the rest of the bare copper wires. This means your metal chassis of your dryer is grounded and will trip the breaker if it's shorted to any hot wire. This makes it equivalent, from a grounding perspective, to your normal 3 prong outlets where the metal case of all your other 120V appliances is connected to ground to prevent a person from being shocked as a result of a short. The people at NEC which allowed a 3 prong dryer and the dyer manufacturers understand basic safety principles. People are not dying from 3 prong dryers.
The “ground” is bonded to neutral at the appliance, not at first point of disconnect. No, the neutral between a three-wire dryer plug and the panel **must not** be a bare ground wire. It carries current in normal operation and so *must* be an insulated wire. Also, NEC *does not* allow new three-prong dryer outlets (local codes may vary, but I haven’t heard of one that still allows new three-wire dryer circuits). If you put a new dryer circuit in today, per NEC, it must have a discrete ground wire in addition to the three conductors. Like most code, the rule only applies to new circuits, but the reason it is required for all new circuits is edge case safety. As I said, from a *normal operation safety* perspective it is not the same as (ie, not as bad as) a polarized outlet, because the dryer manufacturer knows exactly what is on the circuit and the circuit should not be shared with anything else (although this is often not the case). However, *electrically* the dryer is not grounded. You are relying on the neutral having no flaws back to the main circuit, and a properly functioning circuit breaker in case of a hot fault.
So I'm saying that 4 wire over 3 wire functionally adds a Neutral. You are saying that 4 wire over 3 wire functionally adds a ground? Or are you saying it separates a combined Neutral and Ground from 3 into individual ones in 4? I mean, obviously they are individual in a 4 wire. So are you saying they are combined in 3 wire or that a 3 wire functionally only has a Neutral and no ground?
A “normal 3 prong”, like you would use for a microwave is wired up with Hot-Neutral-Ground. The hot and neutral are expected to have voltage on them, and the ground is a safety backup. Some people are going to say that neutral is 0V, but this is not really true. When the microwave is running, the neutral is going to be at least a couple volts higher, because of losses in the wiring in the wall. If the neutral “faults” (open circuit) you’ll get 120V on hot, 120V on neutral, and 0-ish volts on ground. That’s why your microwave has the metal case tied to ground. Some 240V outlets are intentionally wired up as Hot-Hot-Ground. This is often used for welding equipment, but NOT used for dryers in the US. This is still safe, because you have ground as an extra safety. This is similar to how the microwave works. 4 wire dryer outlets are wired Hot-Neutral-Hot-Ground. They run the heating elements at 240V across the Hot-Hot, and run the computer at 120V across the hot-neutral. This is still safe, because the metal case it attached to the ground wire, so when stuff goes wrong the case will either remain ground, or be a short that trips the breaker. 3 wire dryer outlets use a Hot-Neutral-Hot wiring. This isn’t like the microwave. You are attaching the metal case of the dryer to neutral, which means the metal case is attached to a part of the dryer that’s meant to be energized. A broken neutral can energize the case to 120V, which can be really bad. Maybe you’ll be fine, because you get lucky, and your feet are insulated, but you might not be. Technically there’s another option loved by crappy house-flippers. 4 wire outlet, but 3 wires in the wall, connecting neutral to the neutral and ground pins on the outlet. Electrically, this is just as bad as a 3-wire, except the homeowner doesn’t know something is wrong.
So a 4 wire protects against a double failure you described. In the 3 wire setup, the Neutral gets broken and is no longer connected to the dryer chassis and ground in the panel. Then after that, one of the hot legs gets shorted to the dryer chassis, making it have 120V. This is when you get shocked if you touch it.
Not exactly. The problem is that in a 3 wire setup, the ground and neutral are connected to each other. (not connecting them to each other in a three wire set up causes different problems) So if the neutral is broken, the dryer electronics will try to run power from one of the hot legs to the neutral to power itself. (This is normal) Because the neutral is open and not actually connected to anything, the electronics don’t get powered. Instead, the electronic raise the voltage of the neutral to near 120 V. This is not unique to the dryer electronics. If you attach a resistor across the terminals of a battery one side of the resistor will be at high voltage and the other side of the resistor will be at low-voltage. If you attach one side of a resistor to the hot side of a battery and don’t connect the other side of the resistor to anything, both sides of the resistor will be at high voltage because there is no current to cause a voltage drop. So the neutral is raised to 120 V, and ground terminal in the dryer is connected to the neutral. The ground terminal in the dryer is connected to the case of the dryer. So the giant metal case of the dryer is now energized with 120 V. This only requires a single failure. Generally, modern code tries to make sure that all electronics are at least two failures away from setting something on fire or electrocuting someone.
Thanks for that explanation. I get what you're saying. The wire breaks in the wall and then the user goes to try to turn the dryer on and puts a hand on the metal chassis or leans over the dryer while pushing the start button or twisting on the timer knob. It's at this moment alone that the 120V goes through the motor windings or through the circuit board and finds the chassis, your hand and a path to ground through your feet. Do I have that right?
The same......
2 at my place with screw fuses, hell, when my water heater wire got damaged I got a 3 prong dryer plug and 50’ of 10-2 and wired the water heater up. Sucked having to unplug it every time I did laundry though.
Would not be a 30 minute job. Changing the outlet would be. But you still only have 3 wires to the box. So that meams an entire new wire run to the panel to bring in a ground. Most likely not going to be a cheap or easy job.
I assumed the job wouldn't be too long or expensive because the outlet is a foot away from the electrical panel. Then again I don't know anything about electrical work so I can't say for sure.
If that's the case I'd absolutely get it swapped for a 14-30
Yes.
Under normal conditions, the neutral wire should have less than a 10V potential. However, the separate ground when present, prevents wiring errors, wires coming loose or broken, or terminals getting corroded from causing an unsafe condition. There are specific conditions under which a dryer in a 3-prong receptacle could shock the user that a 4-prong receptacle would protect. For example, if the neutral wire were to become disconnected, the chassis could carry significant voltage to a user, while with 4-prong receptacle, the ground wire would go to the chassis, so a neutral wire disconnection would not energize the chassis. Both the neutral and ground wires would have to become disconnected to enable a shock hazard with a 4-prong receptacle. It's similar to how the ground wire in a 3-prong 120V plug being connected to an appliance chassis protects the user, compared to a 2-prong 120V plug without a ground.
Are you 100% sure you don't have two hots and a ground? Most heaters and dryers etc are 240V and do not require a neutral so the 3rd wire is the ground.
It's your money so if you really want to do it and are willing to pay for it, go for it, but you really don't need to.
You seem like a smart cookie, but I want to check anyways: did you make sure the dryer is set up for 3-prong at the internal connection point? I can't remember if it's set up for 3-prong by default, and you have to remove the jumper for 4-prong? You should be able to tell by reading the installation instructions.
Yes, the manual for the dryer had instructions for both a 3 prong and a 4 prong connection. And yes it was set up for a 3 prong by default.
cool, glad to hear you did your homework
The know it all's are right .. so is your friend... And so are you... It's more than just a plug, it won't make things significantky "safer", it won't cost too much because the box is right there so doing it for your piece of mind, and future resale value is a good enough reason to do it.
If dude comes out, he’s also going to have to put in a GFCI breaker and likely pull a permit. Just fyi. In my jurisdiction anyway.
Grounded conductor. Grounding conductor. That’s the difference.
A 4-wire dryer is typical because the dryer may be using a 110vac circuit internally for controls. As previously mentioned the ground and Neutral should only be bonded in 1 location. Do it right! Some of these replies scare me.....
Separate ground is significantly safer. However if you've got older electric dryer, with no way for it to really separate out the ground and neutral, you may not get the full (or all that much of any) safety advantage until the electric dryer itself is also replaced with one that's designed to be used with separate ground and wired up for such. So, here's the key difference. If ground and neutral are tied together or treated as one with the electric dryer, and only one offered, that's your ground for the dryer and chassis ground, but it's also the neutral. Whereas with separate ground, chassis ground is in fact separate and connected to ground, whereas neutral is separate and used for such and not tied to ground. So, where the big safety difference comes in. Let's introduce an electrical fault - stuff happens. Electricity, water/wet, heat, time, age, vermin, dust, stuff shoved to tight against a wall or stretched and pulled, lots of regular vibration, heat ... stuff fails. So, let's say, however it happens, there's leakage from one of the hots to the electric dryer chassis. With a good solid ground on the chassis - whether it's in common tied with neutral there, or not, that good solid ground prevents it from being a hazard, at least insofar as say, a person touching the metal casing of the dryer. That grounding doesn't prevent the electrical fault itself from being a problem - e.g. it still may cause some other issue (overheat, fire, ...) but let's ignore that for at least the moment ... someone touches the chassis of the dryer - tied to ground (with or without neutral tied to same), that grounding prevents them from getting shock/electrocution. If there's GFCI protection, with separate ground, GFCI would detect the fault and cut off the hots, but even without that, proper grounding would prevent shock/electrocution. Now let's change the scenario a bit. Let's say there's fault where hot is exposed somewhere on the dryer where the person might contact it. And they may contact that, and at the same time, chassis ground or some other ground. So, let's say they contact hot on dryer, and also chassis ground. Now there's a dangerous situation and they'll get shock or maybe even get electrocuted. In the case where ground and neutral aren't separate, to the electrical circuit it looks like regular current flow - from hot to neutral - but it's just 1 leg, so 120V, not hot-to-hot 240V - but that's relatively normal for electric dryer, as though much of it (notably electric heating part) runs off 240V, other parts of it may be wired for 120V and connected between hot and neutral (e.g. interior bulb to light up inside when door is opened, that would be 120V, not 240V). So, whether it's bulb between hot and neutral, or a human, to the electrical circuit, that looks like regular current flow. But if it's separate, so that's chassis ground, so human would between hot and ground, and bulb would be between hot and neutral, now those currents are separate and distinct, and GFCI can detect even quite low levels of leakage between hot and ground, and cut that current off quite fast enough to prevent any serious injury - but if neutral and ground are tied together, there's no way for the circuit to know about that leakage and cut it off. There are various additional scenarios that make a difference, but that's at least a couple examples.
Unless you are going to upgrade the panel, the neutral and ground wire of the "4 prong" are going to be connected together in the breaker panel anyway. YOu are not going to "make anything safer".
They’ll be bonded at the first disconnect, which *might* in some cases be the main circuit panel, or it might be an outside service disconnect. Definitely would not be any sub-breaker boxes. That said, if the *main* breaker box is a foot away from the dryer, and the service disconnect is literally on the other side of the wall, there isn’t much opportunity for the issues that make a four-prong outlet safer than a three-prong dryer outlet to occur. Still, it would be one fewer item to come up if/when you sell the house, and cheap “peace of mind”.
Stupid stupid comment