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In Reply to: Re: ? about a Cheater plug to eliminate hum---might this configuration cause "death"? posted by StephenJK on April 6, 2007 at 17:30:20:
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
Follow Ups:
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
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