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We have all read about the possibility of electrocution or even death by lifting the ground on an electronic component to eliminate a hum. I recently had to do this to a preamp and am wondering if in my configuration that the use of the cheater plug might be harmful:I have an amp, preamp, and a few source components plugged into one of those $500 Monster power conditioner jobbies. The cheater plug is used on the cord from the preamp INTO the Monster conditioner, and the Monster conditioner is plugged into the wall using all 3 of it's prongs. With this configuration, I eliminated the hum, but am wondering if I am "protected" from shock and or death because my Monster is still earth grounded. Am I or not? I see this issue come up once in a while but can't find my question ever posed.
Follow Ups:
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For starter we're not exactly talking brain surgery here, the purpose of safety ground is easy to understand.Second it seems to me that while having a safety ground obviously does provide protection over having none at all, it is also true that there is an element of a false sense of security. The sort of fault were talking about here, the hot wire becoming disconnected and contacting the chassis, is a *major* fault. Hence who's to say that such a major fault didn't likewise involve a disconnection of the safety ground wire?... certainly it's not *impossible*.
Double-insulation likewise carries the same risk... who's to say the fault isn't one which involves the hot wire coming in contact with the outer shell?... certainly it's not *impossible*.
The only complete protect involves having a non concuctive shell and controls... remember those old plastic radios?
Lastly, anyone who would put up with hum for fear of getting a 120V shock... and I can personally attest that, 1. I've had a few, and, 2. I'm not communicating from the grave... doesn't deserve to be called an audiophile as far as I'm concerned!
Save me, save me... from over-zealous engineering safety nuts!
LOL
You said that:"Lastly, anyone who would put up with hum for fear of getting a 120V shock... ".
Yes, chopping off the ground pin works. So does taking the battery out of an annoying smoke detector, or putting "pennies in the fuse box" as they once did. But these are not the proper ways to fix these problems.
Your assertion would be valid if defeating the ground pin was the ONLY way to solve the problem. But it is not. It's a JIRY RIG - a WORKAROUND for those who lack the ability to correct ground loop problems the RIGHT way. If anyone should be stripped of the "audiophile title" it's these amateurs that needlessly defeat a safety mechanism because it's easy and requires no self-education about ground loops and what REALLY causes them.
Then again, I think being called an audiophile is somewhat of a negative reflection of ones overall psychological condition and is not a title I'd be really afraid of losing anyhow.
But one thing is for sure: cutting off a ground pin because of a ground loop is as sensible as cutting off your head to cure a headache.
Anyone willing to learn anything from this thread has already done so. bjh is just using this thread for mental masturbation purposes.
Do you buy lottery tickets?
we learn that there are 1000 Americans killed by electric shocks every year. My goodnes that is a whopping 2% of those killed by smoking! Oh wait, that's based on deaths due to second hand smoke (estimate 40-60,000 per year), if we compare with smoking mortality proper, i.e. smokers, then that 1000 comes to 0.25% (of 400,000 a year).Perhaps you and your like can exert your energy where it could do more practical good? Just a thought.
LOL (and I told you not to make me do that!)
It's one thing to say, "Statistically, this is unlikely to affect me."It's an entirely different thing to actively increase your chances of becoming one of those statistics.
You are certainly free to rationalize your choices, and AFAIC you are free to harm, maim, or kill yourself as a result of your rationalizing. Just make sure there's no chance that your choice to deliberately ignore safety features and regulations will affect anyone else.
I promise not to invite anal-retentive safety types over for a listen, how's that?
bjh, your post relates only to a bared hot conductor coming into contact to chassis condition, and I agree that possibility is remote. On the other hand voltage leakage through a primary winding of a power transformer is possible and does happen on occasion.If you are talking about an audio system that is in an audio room with limited access sure then maybe no big deal. But if the audio system is in someones living room where possible access by small children or the like then safety should be a concern. Children like to touch things with both hands at the same time. Sure they have been told to stay away from dad's or grand paw's audio system but when someones not watching, kids will be kids. The deadliest current is between 100ma to 200ma. A leakage voltage as low as 50Vac could harm a child.
Face it, like I believe you were trying to say in your first post, the possibility of the owner user of the equipment receiving an electrical shock maybe remote. Sure if the floor is wood or carpet that eliminates a current path from a hand across the heart through say bare feet. And the chances of a user owner having one hand on a ground lifted component and the other hand on a grounded component is remote. I mean the old rule of thumb if it might be hot make sure your body is insulated from any grounded object and keep one arm behind your back.
What fraction of the general population comprises audiophiles? What fraction of the general population disables the grounds on their electrical appliances?
is a desperate cry for help, or a pre-Easter fundamentalist tent revival! I suppose it makes sense that, if bjh is such a daredevil, he's got some snake-handlin' in his past. Praise the Lord, and Hallelujah, my stereo shall rise again!Hey, if you want to clip the ground prong on every cord you own, feel free. As I said in a previous post, in the greater scheme of life the chance of disaster is probably small. You can also prop that "old plastic radio" on the edge of your bath tub-and gfic be damned! NEC codes are for Losers and Whiners. After all, you're an audiophile- Danger Is Your Business!
Seriously, do as you see best. I just like to show a different perspective so people see both sides, and that allows them to make an educated decision. Right?
I've been bitten by 110/120 before also, (who hasn't) but that's not the point. Your body's resistance to ground at the time of conductance will determine whether or not your muscles contract, and you can or cannot release the metal. If you cannot, fibrillation will soon follow. Believe it or not, 110/120 can be more dangerous in this regard than higher voltages.But, as I said....
I'm using a cheater plug to plug a three-pronged connector into a two-pronged outlet. I've unscrewed and replaced the center screw through the green loop that goes off of the plug; in theory, this acts as a ground by coming into contact with the piping and going down a water pipe to ground. This probably isn't true with newer houses, but I live in an older one (1950s) and there are indeed pipes behind the outlets designed to carry current to the water pipe which goes to ground.I've read that this ground connector actually isn't an adequate ground at all. But green = ground, and I don't think they'd allow a device (for decades, even) that lulls the owner into a false sense of security then kills him.
Should I worry? In either case I'm not going to give it up and get it grounded, because I'd really have to have the entire house grounded, and I can't afford it. So my options are to essentially bankrupt myself or to stand an extremely remote chance of death; I'm willing to take the risk. I'm just wondering if what I've heard about the center screw being an inadequate ground is true.
I'd imagine that most cheater plugs are used to float grounds and not for their intended purpose (i.e. to convert three prongs to two safely), and so the green loop isn't connected to anything which would obviously be a hazard, but I don't know.
If you're using a center plate screw and a "ground adapter" it's probably because you don't have a three-prong receptacle and wish to use a device with a three prong cord end.If this is so, you have a two-prong receptacle and probably also have two-wire branch circuit wiring to that receptacle.
If THAT is so, then you have no dedicated safety ground. All you have is a hot wire, a neutral wire, a non-self-grounding 2-pole receptacle, all tucked neatly inside a metal box that is nailed to a 2x4 and adjacent to a sheet of drywall.
So where is your path to ground in all of that?
Those who decree "No worries, the neutral is grounded!" are failing to understand we're not talking about a short from hot to neutral - as this would result in a ground fault that would almost certainly open the breaker with EITHER type of receptacle EVEN with the ground pin removed. (Ground is not involved with a L-N short.) But we're talking about a short from the hot to the CASE - NOT to neutral. Neutral is grounded AT THE PANEL... NOT AT THE CASE!
It's even worse if you're in your garage and there is a metal cover plate instead of a plastic one. If you get a short to the case, your trusty little "ground adapter" is simply going to energize the metal cover plate as well. Now, if you don't get electrocuted by your appliance, you might get electrocuted trying to unplug it!!
Nobody is mentioning the best solution for this: have an electrician run at least one modern 3-pole branch circuit to the vicinity of your gear to service your 3-pole appliances. Let's face it - where are you going to have more plugs in your home than behind your TV/AV rack or audio room?
People in these threads are balking at the cost of electrical work in their homes, but talk about spending $10K on speakers.
I just don't get it.
Cheers,
PrestoP.S. If you DO for some reason have a 2-pole plug on the end of a 3-pole branch circuit (aka Romex with ground wire) that's the easiest fix of all. Simply kill the breaker, remove the 2-pole plug, and install a 3-pole plug and connect H, N and G wires to their respective terminals.
So why are they allowed to be sold at all? I don't get it.In my case, it's not that I'm running out to buy $10K speakers and neglecting the circuitry. My entire system cost about $2000 and took maybe six months to get enough extra money to afford it... I'm definitely on the far low end of the high-end spectrum. It's easy to get great stuff on a budget if you know where to look and have a little bit of patience. Doesn't mean I've got the cash to go throwing at electricians, unfortunately; call me reckless but I'll take my chances. Electrical outlets were around for almost a century before the ground pin was invented; people didn't drop like flies then, even with big power tubes being the norm. Sure it was more dangerous then, but it was hardly a catastrophe.
> > Electrical outlets were around for almost a century before the ground pin was invented; people didn't drop like flies then, even with big power tubes being the norm. Sure it was more dangerous then, but it was hardly a catastrophe. < <Depends on your definition of "catastrophe." According to the US Fire Administration, residential fires caused by electrical faults kill approx 485 Americans and injure 2,305 more every year. About 1000 Americans are killed by electric shocks every year, and many more are injured.
This death toll totals to 10 times the number of people that were killed in the Oklahoma City bombing, which was definitely a catastrophe, and is roughly equivalent to the number of people killed as a result of Hurricane Katrina.
what part of the country you live in. It is my understanding a lot of older homes in the NE were wired in BX. BX had a flexible metal armor around the two insulated conductors The metal armor is connected at the panel board and rough-in box by connectors. Problem is corrosion over the years my effect the conductivity at the box fittings.
I'm using a cheater plug to plug a three-pronged connector into a two-pronged outlet. I've unscrewed and replaced the center screw through the green loop that goes off of the plug;
Unless the metal rough-in box is grounded you do not have a ground. You can check to see if the box is grounded by using a volt meter. If the old 2 wire receptacle, outlet, is polarized you will see that one slot is longer than the other. The shorter of the two is the hot conductor contact. If you measure from this slot to the center trim screw you will read 120V nominal. If the receptacle is a non polarized type measure from each slot to the center trim screw. If the box is grounded you should get a measurement of 120V nominal from one of the two slots.NEC does allow a wire to be installed for an equipment grounding conductor for an old 2 wire type receptacle to be run to a cold domestic water pipe and bonded, connected, to the water pipe with an approved water pipe ground clamp. Replace the old 2 wire receptacle with a new 3 wire type.
Another option is to replace the old 2 wire receptacle with a GFI receptacle. NEC allows this. A GFI receptacle does not need an equipment ground to still operate.
NEC does allow a wire to be installed for an equipment grounding conductor for an old 2 wire type receptacle to be run to a cold domestic water pipe and bonded, connected, to the water pipe with an approved water pipe ground clamp. Replace the old 2 wire receptacle with a new 3 wire type.
Correction, not any more..... I checked NEC 2005 NFPA and it is no longer an excepted method...... The new equipment grounding conductor would have to be ran back to the panel the branch circuit is fed from.
Acutually to make sure you have a good positive ground I would suggest after using the meter you should use a load of some type. A meter will tell you you have conductivity but will not tell you how good the connection or the conductivity is.A simple load test would be to use a pigtail socket and a 100 watt light bulb. If the bulb lights full brilliance that is good. If the light is dim that's not good. Poor connection....
Hello,In a 120V country, like the U.S., one of the leads is hot, the neutral lead is actually attached to ground at the fuse box, and, in recent years, outlets incorporate a 3rd ground pin. This means that every 120V appliance, whether it has three wires or two, actually has one ground attachment as is. But this is not a safety ground, because if the hot lead in a metal box appliance somehow breaks loose, or shunts through a defective component to ground, it can elevate the chassis to "hot", or 120V, unless there is a safety ground, which is the purpose of the "ground" conductor.
However, this is extremely unlikely to happen in an appliance. Consider plug-in lights, ie., table lamps, and floor lamps. In the U.S., these are all two wire devices, typically with exposed metal work. If the zipcord in these lights somehow becomes frayed, and the hot conductor touches the metalwork of the lamp, the lamp will become hot. If someone touches the lamp, and a good ground, he could be electrocuted. But, the NEC, obviously based upon a very careful risk assessment, does not require the metalwork of the lamp to be grounded by a safety ground. The NEC authors do not think it represents a significant shock hazard in the enviroment in which the lamps are typically used. However, in kitchens, and bathrooms, where water and plumbing are at close hand, the NEC has more stringent requirements.
For many years, audio equipment was manufactured with two wire plugs as well, up to the early 90's, in some cases. The manner of construction of most of this equipment is identical to equipment specified for three wire safety ground operation. Internally, there is no difference at all in the safety considerations of the transformers for these devices. Since the early 90's, all this two-wire equipment has had polarized plugs. There is a reason for this. One is that it is desirable that the on-off switch must break the hot side of the circuit. The other is to take advantage of the fact that one of the two prongs on the power cord is actually at ground potential. When a transformer is wound, one terminus of the winding is at the iron core. The other is on the outside. When the inner winding termination is connected to neutral, this provides protection against a transformer short. Even if the inside of winding shorts to the frame, which is extremely unlikely, it will not elevate the potential of the amplifier chassis above neutral, which is actually at ground potential.
The only other way a 2 wire amplifier, hooked to a 120V circuit, could present a hazard is if the hot side of the line cord actually breaks away and contacts the chassis. But there is no more risk of that than with a plug in lamp, for which the NEC approves 2 wire operation. So, if the polarized plug is plugged into a properly polarized circuit, a two wire stereo, OR a three wire stereo with the ground lifted by a cheater plug, is no more dangerous than a residential plug in light. Eventually, the NEC moved to a higher standard, "double insulated." Modern two wire equipment requires two separately identifiable insulating layers. However, if the line cord breaks off internally, a chassis short could occur. In a 120V environment, there is not much difference between so-called double-insulated and single-insulated equipment.
This is not true in a 220 volt country. In this case, neither lead is at ground potential. A transformer short in a two wire device will result in elevation of the chassis above ground. The "double insulated standard" is meaningful for two wire devices. Combined with the higher voltage, one should take a little more care.
Hope that helps,
Pande:Hmmm... sounds to me like you're knowlegable enough about things electrical. So your take on all this is that a short to the case is simply not very likely? That is what I get from your post.
I guess it's not very likely to get hit by lightening either - so do you keep golfing or swimming during an electrical storm? I mean, what are the chances your plane is going to go down? Why put on that uncomfortable seatbelt just because a light comes on telling you to do so?
What I am trying to say is this:
Those who seem quite knowlegable about electrical systems can decide for themselves if they want to follow electrical code and use life-safety mechanisms. They may even know the risks of doing so and how to manage those risks. But I think it is a grave irresponsibility to downplay the potential risks of failing to use proper house wiring methods. It may even prove to be a liability.
My response to your take on this issue is this:
LAYPERSONS:
1) FOLLOW ELECTRICAL CODE.
2) Get your installations inspected.
3) Do not advise others on electrical code.
4) Do not do electrical work in others homes.
5) Do not cut ground pins off of your appliance cords
6) Do not use "ground adapters"It's that simple. It's not about probability and statistics. It's about code, law, and a responsibility those who are trained in electrical have to help with public awareness. Sure faults to metal cases are not common. There are also only 200 or so consumer electrocutions per year. So why give our friends here at the Asylum a chance of being one of them? Even if it is a small chance?
Do you play the lottery Pande? I do. But despite the really poor odds, in that case I hope to win. People win the lottery all the time. People get electrocuted all the time too.
What a way to die - from a "statistically unlikely" cause of death that was completely preventable and avoidable!
Hello,Statistically speaking, a short to the case is unlikely. Perhaps one audiophile has been killed in the past 20 years by an electric short, while 1000 have died in car crashes, and 100,000 from old age. That does not mean I am trying to downplay the risks or advocating the use of cheater plugs; I leave that up to the individual who has well informed himself about managing those risks. I concur with your advice about following the electrical codes in your area. There are also other considerations that may not have been mentioned, such as insurance. OTOH, an argument may be made that singling out hazards that are almost hypothetical will neither increase our life expetancies, or our enjoyment of life. Eventually, most of us will die in bed.
You are well advised to follow local codes and laws, but if you choose to use a cheater plug regardless, some common sense directives are in order; don't use your amp as a place to park your ass. Don't grab it while searching for a water pipe to hold onto. Turn the system off before you make mods. In any event, you can plug the cheater plug into a ground fault circuit interrupter (GFCI), which will provide protection similar to what the troublesome ground connection provided, without the hum.
I do not play the lottery. The government gets enough from me by way of taxes. :)
Pande
Excellent explanation! Have you ever been a teacher?
Hello,Yes, I have taught once upon a time ago, but in an industrial setting, not an academic one.
Consider plug-in lights, ie., table lamps, and floor lamps. In the U.S., these are all two wire devices, typically with exposed metal work. If the zipcord in these lights somehow becomes frayed, and the hot conductor touches the metalwork of the lamp, the lamp will become hot. If someone touches the lamp, and a good ground, he could be electrocuted.
Maybe true with older lamps not sure that would be the case with lamps sold in the last several years.
When a transformer is wound, one terminus of the winding is at the iron core. The other is on the outside. When the inner winding termination is connected to neutral, this provides protection against a transformer short. Even if the inside of winding shorts to the frame, which is extremely unlikely, it will not elevate the potential of the amplifier chassis above neutral, which is actually at ground potential.
Good in theory but in reality, at least High-End gear, manufactures will connect the primary leads of the transformer either way for their polarity check of the power supply of the equipment.
This is not true in a 220 volt country. In this case, neither lead is at ground potential.
You may want to check. My understanding one leg is intentionally grounded becoming the the grounded conductor, neutral.
> > .
Many audiophiles use ground cheater plugs, you do take a risk when using them.The chances of a frayed hot conductor in a piece of equipment happening would be very remote at best. More likely
what could happen is the insulation on the primary winding of the power transformer could fail and the winding conductor come in contact with the iron core or any other metallic part that is connected mechanically, conductive, with the case (cabinet) of the equipment. The amount of the difference of potential, voltage, to ground would depend on where in the winding the leakage, or fault, occurred. If the leakage or fault is nearer the side of the winding closest to the neutral any difference of potential would be small when measured to ground. If on the other hand the leakage or fault in the winding was nearer to the hot conductor then the difference of potential from the case to ground would be higher.If you do use a ground cheater on your equipment I would suggest you unplug the equipment using the ground cheater when ever disconnecting, changing, ics. Small leakage, faults will travel on the signal ground of the ics to a grounded piece of equipment and find its path back to the source though the equipment grounding conductor of the grounded piece of equipment.
If a fault is present and the lifted ground piece of equipment does have a leakage you could receive an electrical shock if you put yourself between the ics shell and the case of either end of the ics....
Just to make things a bit more complicated, I thought I might raise another point about ground wires and ground connections. When you buy your Tektronix 100 mHz digital dual trace storage analyzer/oscilloscope, you may notice that the 3-prong supply cord comes with an adapter. The adapter is a 3-prong inline plug with the ground pin removed to provide ground isolation.A lot of oscilloscope tests can be done with the common side of the probe connected to ground, but any signal that is through an isolation device will be pulled to ground if the cheater plug isn't used.
You might not think it's that big a thing until you go to check a pulse transformer on a 350 A power switching SCR, and without the cheater plug you pull down one side of an AC regulated circuit....
You might not know right away what the problem is, but you certainly know it's a bad thing.
Based on my internet research.
You could look it up.
You can trust the internet right?
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Richard BassNut Greene
Subjective Audiophile 2007
You mentioned a cable box. Man, I hate cable TV.Actually, any cable or antenna will likely cause hum. My FM antenna does. The strange one is I didn't have any hum and then started noticing a problem. I tried a couple cheaters and switched plugs around. Finally, I checked the cable box and disconnecting the cable fixed it. But that wasn't going to work if I want to watch TV.
The cable box is connected via Toslink to a processor. So, for grins, I disconnected the coax from the DVD player. No, problem. Hmmm.
I'm really confused. Then I only disconnect the DVI cable from the DVD player. No hum. What's going on?
Well, the cable box is connected to the projector and the projector is connected to the DVD player and anything connected to both the projector and processor make for the cable ground loop to get transmitted through.
So here's the fix. If you disconnect the cable from the box and don't have hum, then you need an isolation transformer. You can buy one from audioadvisor or somewhere. Does anyone know if those are any worth the money? Or you can go to Radio Shack and buy a 300 to 75 ohm transformer and a 75 to 300 ohm transformer. Connect the two together, so you have the correct 75 ohm ends to connect to the box and cable and you've isolated the cable ground.
It works like a champ, thank you Jon Risch. However, the Radio Shack kludge does have some loss. On my FM antenna, it's no an issue. On cable, the HD channels didn't like it. That's why I need to better one.
Anyone got any recommendation?
I have the same problem, this works for me.
MCM makes good and cheap RF isolation transformers. They work!
Isn't it interesting how everyone has an expert opinion. It's like this. Residential power supplies in North America are with a 3-wire 120/240 VAC system. That is, with two "hot" wires and a neutral. The voltage is measured between the two hot wires at 240 volts, and between each hot wire and neutral (or ground if the neutral is grounded) at 120 volts. The 240 volt supply is used for your stove, clothes dryer and air conditioner, the 120 volt supply for everything else. The only reason that the 240 volt supply is used is because power consumption, or Watts, is a multiplication of volts and amps. By doubling the voltage to 240 for the big loads, the size of the supply wires and the breakers can be cut in half.As the power supply is AC, at 60 Hz, that essentially means that the generator from the utility has the job of moving electrons back and forth 60 times per second.
By code, the neutral is called the "grounded" conductor, the ground wire is the "grounding" conductor. In most jurisdictions, the neutral must be grounded, but at one point only to prevent ground loops. This is generally done at the distribution panel, where it can be easily inspected.
With a stereo system, every power cord will obviously have a hot and neutral wire to provide 120 VAC to the component. Some will have a two-wire connection cord, some will have three. Those with three will have a ground wire connected to the frame or chassis ground of the device.
That being said, the ground path through that device may be at a different potential from the ground of the duplex receptacle that is supplying the power. With a difference in potential, and a resultant voltage rise, this can cause a current through a ground loop that can cause an audible hum.
Lifting the ground of the amplifier by either breaking off the ground pin or using an adapter plug with the ground removed is a well recognized means of preventing or reducing problems with ground loop hum through the speakers.
If this was truly a death defying situation, then why do they sell appliances and devices with only two-pin plugs as opposed to three-pin?
In fact, my Bryston 4B amplifier has a switch on the back labelled "Normal" and "Separ" for separate which lifts the ground pin if there is a ground loop hum problem.
Any risk or danger of electrocution is only possible if the hot wire becomes connected through a major fault to the metal frame or chassis of a component. If that were to occur, with no ground wire, and the grounded neutral wire was through a high resistance, there is a chance of getting a shock. With a separate ground wire connected, the hot wire would have a low resistance path to ground that would trip the supply breaker or blow a fuse.
With stereo equipment, however, the supply power being connected through an isolation transformer or a step-down transformer will introduce a high impedance path that will cause a trip on the primary side only. That is, if your cat chews through the supply wire to your amplifier, the breaker will trip. If something happens internal to the component on the step-down side of the transformer, separate protection is required.
If anyone has concerns about whether a two-pin Hot/Neutral wire is safe or not, just have a look around your house at your floor/table lamps, kettle, toaster, etc.
A ground wire is most definitely a personnel and equipment saving means, but remember, if your electrical supply system was properly installed, the neutral wire is grounded.
Two wire appliances, such as hand-held drills and other power tools, are "double-insulated", meaning they have no metal parts that can readily become energized, even if an internal hot wire becomes completely detached.Three wire plugs have a ground wire that is used on appliances with metal enclosures that CAN become energized in the event of a short circuit (i.e. frayed hot wire, hot wire come loose, component failure, etc.).
In normal operation of a three wire branch circuit, when an enclosure becomes energized, the ground wire (via the ground PIN) provides a path for the fault current to return to source. Since the breaker is on the 120V (hot), the breaker "sees" the fault current and trips very quickly. This is because the fault current magnitude is high, because typically the impedance of a short circuit is quite low. (This is why it is called a "short" - it's an abnormal path where the source voltage goes directly to ground, instead of driving the loads in the device it is intended to drive.)
If you cut the ground pin off, you do NOT have the same appliance as a typical two-prong appliance. You have an appliance that was DESIGNED to RELY upon that ground pin in the even of a short that has it's main safety feature completely disabled! When a short to the case occurs when the ground pin is removed, the enclosure remains energized, but no fault current can flow (except for a small current due to capacitive coupling which is insufficient to trip the breaker).
Touching this enclosure can result in a deadly amount of current flow in the human body - just enough to send the heart into fibrilation. This is the deadliest type of shock. Shocks less severe only cause small contact burns or discomfort. Shocks more severe will completely stop the heart, but in this case the heart can be restarted.
When a heart is in fibrillation, it spasms uselessly and cannot provide life-sustaining blood pressure.
The bad news is that only a defribulator can stop fibrilation. This is (oddly enough) a controlled shock which is actually used to stop the heart (not start it like on TV). Sometimes the heart re-starts by itself after a shock from a defibrilator, but failing that, adrenaline is administered to the heart muscle directly, or the chest is opened and the heart is massaged manually.
If you have humming equipment, you have defective equipment, branch circuits, or improper or faulty interconnects. Fix these problems - but do not remove that ground pin.
And avoid listening to misinformed laypersons that believe it's "not a big deal" to do.
Cheers,
Presto
the chances of a metal cabinet powering up, and your body's resistance to ground being low enough to cause fibrillation, are remote, but why take a chance?A personal experience highlighted this danger to me. A carpenter on a job I was on was using a skilsaw (the old metal-bodied style) while standing on a scaffold. His saw shorted out, and because his arm and hand muscles contracted from the current, he could not let go of the saw. Finally, in desperation, he jumped off the scaffold, the cord hooked on the way down, and the saw came unplugged. There was no one around at the time-if he had not been able to stop the current, his heart would have fibrillated, with potentially dire results. For me, lesson learned.
Powermatic:Did you know that falls as a result of electric shock is very common? Electricians have this addage "If the shock doesn't kill you - the fall just might!"
This guy may have made a life saving decision. When you're being shocked and you cannot let go, if you cannot throw yourself with sufficient force to either remove yourself from the device or unplug it... you're done for! Not too many people even have the presence of mind to take such action during a sudden violent shock. Others may face falling to their deaths if they attempt to jump or leap away from the source of the shock. Not a desireable situation at all.
Questions to ask:
1) Was that "old tool" a two-wire double insulated tool? With metal parts - not likely.
2) How much is a new double insulated or properly grounded skil saw?
3) Why did the carpenter wait until he was almost killed to buy the new skil saw, or at least inspect the tool to ensure it was safe?
A very sobering story. Thanks for sharing that.
The saw of choice for pros, and least on the western side of the country (easterners seem to prefer the sidewinders).This model has remained unchanged for a long, long time (sorry, don't know exact time lines, but well over 50 yrs). This is the latest iteration, but the only real difference between this and much older models is the resin pistol grip, trigger, and top handle, which were previously all metal, like many tools of the period (drills, etc) and the grounded cord. The older, all metal, no-ground type was the kind Rob was using at the time, and it definitely was not double-insulated. The change to the resin parts was done at least 20 yrs. ago. The newest models are 2-wire/w ground, with the ground presumably attached to the magnesium body.
The good/bad with the worm drive skilsaws is that they will, almost literally, last forever. The gear box is oil filled, and I've never heard of a gear failure (new parts are available, though). The brushes are user-replaceable. Armatures eventually wear out, but those are easily rebuilt. The only part that tends to need replacement is the 'foot' (base) that tends to get bent when it's dropped.
The 'bad' aspect of this equation is that there are still lots of the all-metal ones around, and who wants to give up a tool that his granddad gave to him, and still works great?. However, these can be used safely by (a) always plugging into a gfic receptacle (b)attach a 2 wire/w grnd. cord with a solid connection to the metal body (c)wrap handles with tape.
As far as safety on a job site, well, I'll just say that you would not believe some of the shit I've seen. Just skilsaw-wise, some carpenters wire the blade guard up (makes it easier to start a cut)-while many (most?) wood shake and shingle roofers remove the guard completely! It doesn't take much imagination to think about what that spinning blade would do if you accidentally hit the front of your leg as you drop the saw to your side.
The link shows current prices for skilsaws. The black-handled worm drives are the same as the red-handled, just heavier (and cheaper).
- http://www.amazon.com/s/ref=nb_ss_gw/102-2292484-5623340?url=search-alias=aps&field-keywords=skilsaw&Go.x=11&Go.y=8&Go=Go (Open in New Window)
I have not had to wield a saw all day every day but you are absolutely correct about the east vs. west difference regarding the preference of worm drives and sidewinders!My 5150 consumer grade sidewinder is at least 20 years old, well used in a DIY/handyman sort of way (including cutting concrete and cast pipe with abrasive blades).
the company is now owned by Bosch. They'd be idiots to do anything to undermine the reputation for durability that this saw has.The sidewinders have certain advantages (lighter, startup torque doesn't twist the saw), but also disadvantages (the 'line of sight' on the 77 is on the left which is perfect for right-handers, the linear motor makes it easier to cut straight lines(at least for me (-:), and the gearing gives it a bit more torque). In the end, you pick your poison, get out on the deck, and start cutting up some damn studs!
...that even the best made tools are not immune from electrical failure.Perhaps moving to a moulded handle was for electrical isolation reasons...
If the manufacturer has designed the component properly and is using the chassis as a "Faraday shield", lifting the third pin ( ground ) defeats their engineering skills and could potentially lower performance potentials of the system. As always, it is best to track down the offending piece of gear / problem within the installation and fix it rather than lift the ground and band-aid it.Obviously, this takes for granted that the average AC installation has a low resistance path to ground, which may be assuming all too much. Most AC installations aren't worth shit, hence the major benefits that most achieve when installing heavy gauge dedicated lines and cleaning / weather-proofing their grounding system. Sean
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Yes, I thought it was really odd that all the neutrals and grounds got connected to the same strip in the panel. What's the ground for if it's the same as a neutral?I only use cheater plugs when they work, but it's the best tweak in the kit. No worries, I'm still alive.
-Rod
Your use of cheater plugs is dangerous.Let me provide a more simple explanation than the correct ones given so far.
Take a typical appliance or audio component with a metal case. The AC goes in to a power transformer or other device, with both the hot and neutral wires insulated from the case.
If something goes wrong inside and connects the hot wire to the case, the neutral will not be affected because it is insulated from the case. However, the case will be at the hot wire potential. If you touch the case while also touching something connected to earth, you will be killed.
The AC "ground" is a separate conductor that goes back to the entrance panel and is tied to the neutral there. If the ground is present and the case is connected to it, the fault that connects the case to the hot wire will cause large fault current to flow through the ground conductor, which will trip the circuit breaker. This will happen before the case can reach the hot wire potential and harm anybody.
Some appliances and audio components are designed with what is called "double-insulation" and do not need the "ground" wire. Ayre is one maker that uses this approach. The insulation is such that a fault that would connect the case to the hot wire is considered unlikely by the Underwriters Laboratories.
Cheater plugs defeat the AC "ground" connection and create the possibility of lethal voltage appearing on the case. Hum from ground loops is a problem in pro audio as well as home audio systems. There is a safe solution sold to the pro audio market: the Hum X from ebtechaudio.com. See the link.
Thanks to Tuckers for finding this device and calling it to my attention. It contains a pair of rectifier diodes wired anti-parallel, and shunted by a 1000-ohm resistor. Diodes have the property of not conducting much below their "forward" voltage of about 0.5 volts, so the pair presents high impedance to small ground loop hum voltage, but low impedance to fault current. The 1000-ohm resistor is there so that devices such as battery backup UPS that look for a ground will see a ground and continue to operate. Audio components don't need the resistor.
Most gear does not "float" the chassis ( because of poor design and cost cutting measures ), but instead, ties the chassis and board to neutral / ground. This is commonly referred to as "star grounding". While many manufacturers actually advertise such a design as being beneficial, it only works effectively in high impedance i.e. tubed circuitry. It is completely useless and actually detrimental for use with most Solid State designs.If the "hot" wire were to come into contact with the chassis of a "star grounded" piece of gear using a "cheater" ( ground lift ) plug, the path to ground would still remain conductive. That is, the current would flow through the interconnects tied to other gear in the system, which hopefully is grounded. This would in turn pop the fuse of the component, IF the component was properly fused.
The exception to this would be if the safety ground of all of the components had been lifted simultaneously and / or one was using interconnects with a very small gauge ground conductor. With nothing in the system grounded, the path to Earth ground is broken, negating the fusible link. With very small ground conductors on interconnects, the conductor itself would break connection, acting much like a fuse itself. Once that connection was broken, the path to ground would also be broken, leaving the voltage on the chassis of the component to seek ground elsewhere.
Other than that, i agree with everything that Al has to say. Start by fixing your AC / grounding system and most all of your problems will be taken care of. If something should come up after the AC / grounding system has been dealt with, it shouldn't be too hard to find the problem or offending piece of junk gear. The most common problem after "fixing" the AC system would be gear that uses old school non-polarized two pronged plugs. In that case, here's a link that may help some of you solve such a problem. Sean
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I appreciate your always posting in order to try to educate. Convoluted EE theorizing to explain away the necessity of the ground pin does a disservice.
Ground does not equal neutral.Neutrals are grounded at the panelboard (aka in ONE place). That's the only "common" thing about them - that one single connection point. Everywhere else, they are different, isolated from one another, and have TOTALLY DIFFERENT purposes.
Netrals: are connected to the tail end of CIRCUITS and carry current back to the source in NORMAL conditions.
Grounds: are connected to metallic components that are NOT INTENDED to be energized, and carry fault current back to the source in ABNORMAL (short-circuit or fault) conditions.
Still think they're the same?
The neutral wire is the grounded conductor, that means that if there is any fault that connects the supply wire to the neutral that it will cause the supply power fuse or breaker to trip.The ground wire, or grounding conductor is intended to provide protection in the event that the hot or supply wire becomes connected through an insulation or component fault directly to ground.
While at first glance it may seem that they provide the same function, that is not the case. The neutral is the return path for the AC supply system, and is part of the two-wire supply scheme. The ground wire, under normal circumstances, will only conduct electricity if there is a fault.
Grrrrr.Picky, picky. Don't mix your grounds.
Of course, code requires the grounds to all be tied together in a box. How's that GFI know the ground wasn't right?
I've got a 4 gang switch box for some lights with one switch for a plug on the common landscape lighting circuit on a GFI from another panel. It took way too long to figure out why the GFI kept tripping.
-Rod
the difference (amperage) coming and going. Any leak, no matter how small, will trip it.
"Man is the only animal that blushes - or needs to" Mark Twain
> > Isn't it interesting how everyone has an expert opinion. < <Indeed. And those opinions are often wrong. Quite wrong. To wit:
> > Lifting the ground of the amplifier by either breaking off the ground pin or using an adapter plug with the ground removed is a well recognized means of preventing or reducing problems with ground loop hum through the speakers. < <
Yes, it is. It's also well-recognized as being the foolish, lazy, dangerous way to deal with ground loops.
> > If this was truly a death defying situation, then why do they sell appliances and devices with only two-pin plugs as opposed to three-pin? < <
Some equipment uses a type of chassis called, "double insulated." There is a significant difference between a grounded chassis and a double insulated chassis. Not understanding this difference, and then treating the two types as the same, is a great way to get an electrical shock.
> > In fact, my Bryston 4B amplifier has a switch on the back labelled "Normal" and "Separ" for separate which lifts the ground pin if there is a ground loop hum problem. < <
Indeed it does have such a switch; however, the switch DOES NOT DISCONNECT THE CHASSIS EARTH GROUND. It switches in resistance between the chassis ground and the signal ground to reduce the flow of noise current.
> > If anyone has concerns about whether a two-pin Hot/Neutral wire is safe or not, just have a look around your house at your floor/table lamps, kettle, toaster, etc. < <Indeed. Most household appliances are double-insulated; something you really ought to try to understand before espousing an "expert opinion."
Hey, sorry, didn't mean to cause a fuss. I've been working with electrical power and control systems for quite a while. Double insulated simply means that the electrical supply cord is insulated, and that the device the cord is connected to is assumed to be non-conducting. Sort of like your plastic bodied electric drill. Mind you, take it outside in a rainstorm, things might be different...
Well, it depends on what type of device you're supplying power to. As I mentioned in my first post, have a look around your house at the type of cords used to connect electrical devices.Anything without an isolation or step-down transformer inside it will not have a separate ground wire, because it doesn't need it. Should your floor lamp have a three-prong plug with a ground wire for the metal shell of the lampholder? If it's such a good idea, why don't they do it? If the hot and neutral wire to the lamp become shorted, the supply power breaker or fuse will trip off.
Anything with an isolation transformer inside will likely have a ground wire connected to the chassis or frame ground.
Stereo systems and electronic data paths are highly susceptible to electrical noise caused by ground loops that create noise along the signal path. Lifting the chassic ground can break the ground loop path and interrupt the ground loop current.
If you look back on electrical systems installed in residential buildings, the earlier systems consisted of a parallel blade plug with a hot and neutral only. Over the years, this was considerably improved to the modern three-prong plug with a hot, neutral and ground.
This was introduced as a safety measure, so that even with an ungrounded neutral or with an isolation transformer the ground wire would provide a low resistance path for an insulation or component fault.
Safer is always better, and electrical systems continue to improve with ground fault circuit breakers/receptacles and now with arc-flash circuit breakers.
But, remember that the original question was, to paraphrase, "If I lift the ground wire on my preamp to eliminate hum, did I create a hazard?"
The question could be re-stated as "Is it possible for me to be electrocuted if my preamp develops a fault between the hot wire and the chassis?"
Moving along, the next question would be "what could cause a breaker or fuse not to trip if the hot wire did become connected to the chassis of the component?"
The only way that can happen is if the hot wire is isolated from the neutral or the ground wire of the supply cord, as seen by the input power protection device through either isolation or a high resistance connection.
And, if that were the case, the power supply could now be isolated from the supply ground or grounded neutral, so that if you did come in contact with it you would be isolated as well.
It's like the old razor transformers that used to be installed in bathrooms. It was a 1:1 isolation transformer with an ungrounded secondary to the two-pin razor plug.
If you did come in contact between an outside ground path and the isolated hot wire, there would not be a shock because the hot wire was isolated from the supply power ground, so there was no current flow.
Mind you, if you went across the isolated hot and neutral, you would be in parallel....
"And, if that were the case, the power supply could now be isolated from the supply ground or grounded neutral, so that if you did come in contact with it you would be isolated as well."How is that so? The chasis is not connected to neutral - of course. The chasis is also no longer connected to ground (thanks to our pin clipping DIYer).
The chasis is isolated from neutral AND ground (no ground pin anymore), so no ground fault current of SUFFICIENT MAGNITUDE to trip the breaker can flow.
But this does not mean anyone unfortunate enough to touch the energized chasis is "isolated" as well. Having no proper path for ground current does not change the fact the chasis has been unintentionally energized, and the safeguard that was designed to isolate the power source (by fault current via the ground path) has been intentionally broken by removal of the ground pin. No fault current, no breaker operation, no isolation. Chasis remains energized.
Your logic here is faulty - and dangerous.
I'm not an electricity guru, but I read something somewhere that made sense to me: as long as interconnects remain in place and any of the components are grounded then there's not much risk. If this is totally false then please, somebody straighten me out.
> > As long as interconnects remain in place and any of the components are grounded then there's not much risk. < <I've seen this nugget of "wisdom" repeated over and over. It's false. Not only that, taking this approach can create a false sense of safety.
There are several things wrong with this notion. The most prominent are:
1. Signal grounds are not always tied to chassis ground.
In this scenario, if a ground-defeated component experiences a fault, the dangerous current will not flow through interconnects. Even worse, a ground-defeated component with signal ground tied to chassis ground could fault, and the current would flow via interconnects to another component that doesn't have signal ground tied to chassis. Now you have TWO components with dangerous current flowing through them.
2. Most interconnects cannot handle fault current.
The typical audio interconnect (the even really expensive examples) uses thin-gauge wiring designed for low voltage/low current, with connectors also designed for low voltage/low current. A ground fault involves high voltage/high current. Even if a fault is shunted through an interconnect, it may fail/melt/catch fire before a fault can travel to a grounded component and cause a circuit breaker to trip.
There are too many ifs/buts/maybes involved when a safety ground is defeated. You may think you are protected, but what if you're not? Do you really understand the ramifications of defeating a safety ground? Do you really understand the design of all the components and how they would interact in the event of a fault? Is attempting to maximize sonic quality by defeating safety features REALLY worth the risk of burning down your house and/or endangering yourself, your family, your pets, and your neighbors?
for putting this in the myth category where it belongs. Dang! I really wanted that one to be true. It looks like ground loops have been re-elevated to "dreaded" ground loops.
It is certainly possible, even if remote.Electricity takes the easiest path available. From a safety standpoint, a ground wire can be thought of as a redundant system or "back-up." While overly simplistic, think of the AC coming in on the hot wire (black or red one in your wall), doing it's work inside your component, and when done, it leaves by the neutral (white) wire. If the neutral path is blocked for whatever reason (wire damaged, etc.) the ground (green or bare in home wiring) provides a second escape path.
If that path is not available and you touch the component, the AC could use your body as the path to ground, doing you damage in the process. You could get anything from a mild buzz to a fatal shock, depending on a variety of conditions.
If you've got a hum situation that is solved by using a cheater plug, then you have some legwork to find the real issue instead of using the band-aid fix.
jjk12:Although other devices plugged into the Monster power conditioner will be grounded (if they have ground pins), the device you removed the ground pin for will NOT be grounded.
Never remove a ground pin from a three-prong cord end.
It's as dangerous as they say it is.
Why did you have to remove the ground? Did it work good to one point and then stop functioning properly? If so, why not fix the "real problem", or call a electrical guy if your really worried about death.
Oh, I intend to fix it this is a temp thing. It's most likely the new cable box installed downstairs nearby. It's more of a curiousity thing here.Because I was wondering that because the Monster is grounded, if the preamp did become "live", would the Monster because it's grounded either trip its own fuse or cause my circuit breaker to trip before death. I guess the answer is "no"?
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