Dear Mike I'm sure professionals like yourself wouldn't dream of ever cutting a safety ground.
Yet it does happen in pro-audio and video installations, even sometimes in the Albert Hall in London at black tie concerts. I know the US doesn't have laws equivalent to Europe's LVD, but I didn't know whether the actions of OSHA and similar bodies had a similar effect to the LVD. All the very best! Keith Armstrong In a message dated 20/03/02 20:04:01 GMT Standard Time, mertino...@skyskan.com writes: > Subj:RE: Pro-audio and ground lifting > Date:20/03/02 20:04:01 GMT Standard Time > From: mertino...@skyskan.com (Michael Mertinooke) > Reply-to: <A HREF="mailto:mertino...@skyskan.com";>mertino...@skyskan.com</A> > To: cherryclo...@aol.com > > Hi; > > What the heck is a "Class I location"? > > I'm serious. There are about forty-eleven different standards, > each of which seems to have created something called > Class I, Class II, and Class III locations. For example, the > US National Electrical Code classifies Class I Locations > (Section 500-7) as "Those in which flammable gases or > vapors are or may be present in the air in quantities ..." > and so forth. > > By the way, you are not going to get anybody to approve > removing a protective ground wire in a hazardous location. > > Judging from the note at the bottom of your email, I > think you mean UL Class I apparatus. This is equipment in > which protection against shock requires connection of accessible > conductive parts to the protective conductor (per UL6500 > section 2.38). > > If so, then you already have your answer. Protection against > electric shock REQUIRES that the conductive parts be connected > to Earth at all times. You may not, never, nohow go > around cutting no ground wires, okay? > > >It has been a common practice over many many years > >in professional audio systems and installations to 'lift the > >grounds' on equipment to cure hum problems. > >So what are your views on removing the safety grounds > >from Class I equipment used in pro-audio systems and > > installations? Can anyone defend this practice or show > >that it is legal in the USA? > > The hell you say! It is most certainly NOT legal, and is > NOT common practice to remove ANY protective grounds!!!!! > > What is common practice in Audio equipment is to provide > a "functional earth" or a "reference earth" ground terminal. > And yes, it is extremely common to provide this option. > In fact, a shielded audio cable almost never works right > unless you float the shield at one end. This is perfectly > acceptable, because the Protective Earth ground connection > remains intact at all times. > > Okay, so I do not doubt you have had some clowns try to > tell you to snip the Safety ground. *sigh* professional audio > seems to be where children go when they want to pretend > to be engineers. But don't judge us by these morons, okay? > > See ya. > Mike Mertinooke >
