ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 ... 12 13 [14] 15 16 ... 22   Go Down

Author Topic: Dangerous AC situation in reception hall - PLEASE READ  (Read 184425 times)

Chuck Simon

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1139
  • Pittsburgh, Pa.
Re: freak accident? help!
« Reply #130 on: May 23, 2012, 11:15:07 AM »

Well, I'm convinced.  I just ordered a Fluke Volt-Alert.  Thank you Mike!
« Last Edit: May 23, 2012, 04:21:41 PM by Chuck Simon »
Logged

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 17176
  • Hickory, Mississippi, USA
    • Resotune
Re: freak accident? help!
« Reply #131 on: May 23, 2012, 11:38:52 AM »

Yes, to all of the above. And you can still buy Neon lamps with a panel-mount from Radio Shack for around $3 a pair. I have one sitting on my desk in front of me.
Fine for one off... surely cheaper in production quantities.
Quote
And I don't think this is the fix-everything solution. But it will indicate if you have one rogue outlet on stage that's been wired incorrectly as a RPBG. The real problem is that even if the DI's ground path wire is heavy enough to withstand the full short circuit current sufficient to trip a CB, it will likely never come to that. I'll have to calculate the resistance of 100 ft of BelFoil drain wire and do the calculation, but I'm pretty sure there's enough series resistance there to reduce the short circuit current into the 30 to 50 amp peak range, possibly even below 20 amps. In that case the CB won't trip, but your snake will simply heat up red hot and melt. Something's going to become the fuse, and Murphy's Law dictates it will be the most expensive piece of gear in the current path.... 
That is the classic question I wrestled with a decade or two ago... Do you go open circuit or hard short... One could argue for wimply fusible link grounds inside products, but this would probably still pass enough current to kill meat puppets, and not clear the fault condition by killing the mains power.

External cables are far easier to replace than fried gear.
Quote
And remember that even if the "good" outlet is wired properly with a GFCI, it won't know there's a current imbalance (because all the shorting current is in the ground wires) and won't trip at 5 mA or whatever. This fault will need to trip the 20 amp panel circuit breaker in the panel feeding the rouge outlet. This fault won't even trip the circuit breaker in your power strip, since it's not in the ground fault path.

This is not a simple problem to address with product design (and I know you are not suggesting that)... it really is a failure by whomever does the outlet wiring, which unfortunately all to often is DIY and/or uninformed professionals.

keep up the good fight.

JR
Logged
Cancel the "cancel culture". Do not participate in mob hatred.

Jonathan Johnson

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3209
  • Southwest Washington (state, not DC)
Re: freak accident? help!
« Reply #132 on: May 23, 2012, 03:39:24 PM »

...I'm modifying an IMP-2 to have a neon bulb in parallel across the ground-lift switch. See diagram...

The potential problem I see is a false sense of security.

If the two devices connected using the modified IMP-2 both have hot grounds (that is, they are both plugged into RPBG outlets), the neon bulb may not light. This could lead a poor fool to believe that it's A-OK, then they fry themselves when they grab a hot mic.

While it's a valuable indicator, it needs to be made clear that the absence of an indication is not an indication of an absence of a problem. (Hah! I'll bet your head is spinning on that last sentence!)

It is but one tool that needs to be used in conjunction with other tools by trained personnel to ensure a safe stage.

Logged
Stop confusing the issue with facts and logic!

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3361
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: freak accident? help!
« Reply #133 on: May 23, 2012, 04:06:57 PM »

While it's a valuable indicator, it needs to be made clear that the absence of an indication is not an indication of an absence of a problem. (Hah! I'll bet your head is spinning on that last sentence!)

Gotta love the English language. And yes, you are correct. That's why I'm an advocate for walking around with a non-contact tester both before you plug into outlets, and also as a final test on mics and guitars after everything is plugged in. I saw an article a year or so ago where someone was suggesting a tongue test, of holding onto the guitar and licking the mic to prove to the guitar players they wouldn't get shocked. I think a non-contact tester such as a Fluke Volt-Alert is a little better way to go.

And my Neon bulb mod is exactly as you describe, just one more testing tool, not the final test. This will become part of my test regimen I always do on stage. I'm proud of the fact that after I started testing outlets back in the early 80's I never got shocked on stage as a musican again, and none of the musicians I ran sound for have been shocked either. Knock on wood, but I think it's because I have a very healthy fear of getting shocked. I used to play with BIG POWER as an IE where they would maybe have found my ashes blowing in the wind if I screwed up the power (like the picture of the poor fools in the previous posting). But dead is dead, so I never take 120 volt shocks for granted.

BTW: Everybody... thanks for all the feedback and ideas so far. If we all work together on this we'll make stages safer for everyone!
« Last Edit: May 23, 2012, 04:13:28 PM by Mike Sokol »
Logged

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3361
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: freak accident? help!
« Reply #134 on: June 11, 2012, 02:17:16 PM »

I've just received a care package from Amprobe for more of my testing, and really like their little VP-600SB VoltProbe. Not only is it on all the time (they tell me a year or more battery life) it runs on two standard AAA batteries. Plus it not only beeps (loudly) and blinks (brightly), it also shakes in your hand when it triggers. Plus it's sorta flat with a pen grip to stay in your pocket. I found it at Sears for less than $14  http://www.sears.com/shc/s/p_10153_12605_SP101A11576S6083631101P?sid=IDx20070921x00003a&ci_src=14110944&ci_sku=SPM6045437007

Also, I edited my original RPBG proof-of-concept video and launched it on a new www.youtube.com/noshockzone channel. It's now available for general public viewing, so pass it on to anyone you know who plugs into an outlet.

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3361
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: freak accident? help!
« Reply #135 on: June 16, 2012, 09:15:35 PM »

Also, I edited my original RPBG proof-of-concept video and launched it on a new www.youtube.com/noshockzone channel. It's now available for general public viewing, so pass it on to anyone you know who plugs into an outlet.

I now have Amprobe INSP-3, Ideal SureTest, and Extech CT-70 Circuit Testers in my hot little hands, and NONE of them will find a RPBG outlet on their own. See my latest video on the SureTest:  http://youtu.be/_04HmpFBxdQ

What's needed is for the manufacturers to add a non-contact AC test function into the ground contact of their GLIT's (Ground Loop Impedance Testers). In the meantime, add a non-contact tester such as a Fluke VoltAlert of Amprobe VoltProbe to your tool kit along with a standard 3-light outlet tester. That combination should identify 99.99% of problems.

As a quick extra, note that if you use a non-contact tester on a 120-volt outlet that's been rewired with 240 volts for the floor buffer in the gym, the VoltAlert will BEEP on both the Hot and Neutral slots, but the Ground will show as OK. That's the hint not to plug ANYTHING into the outlet since equipment damage will surely result from the over-voltage.
« Last Edit: June 16, 2012, 09:20:51 PM by Mike Sokol »
Logged

George Friedman-Jimenez

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 532
  • NYC
Re: freak accident? help!
« Reply #136 on: June 16, 2012, 11:06:29 PM »

Any recommendation among the Fluke Voltalert 1AC-A1-II, Fluke 2AC, or Amprobe VP-600SB Voltprobe?
Logged

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3361
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: freak accident? help!
« Reply #137 on: June 16, 2012, 11:23:29 PM »

Any recommendation among the Fluke Voltalert 1AC-A1-II, Fluke 2AC, or Amprobe VP-600SB Voltprobe?

Well, I've been using Fluke gear for more than a quarter century, and it's NEVER let me down. I've been using a VoltAlert for the last year and can always count on it to work. It's ruggedly built and works every time.

But I've got to admit that I'm a bit smitten with the operation of the Amprobe VP-600SB VoltProbe. I like that it's always on (no on/off switch to remember) and has a really bright light with a really loud beeper and really powerful buzzer. So you can see, hear, and feel it alarm. The Amprobe VoltProbe feels like a sold piece of gear, and I think it will hold up quite well. Plus it uses AAA batteries available anywhere.

I've been carrying the VoltProbe around for a week and really like it. But if you're a Fluke guy, then by all means go with the Fluke.

FYI: Amprobe is owned by Fluke and they're both located in Seattle, so for all I know they're all built on the same factory floor.
« Last Edit: June 16, 2012, 11:29:38 PM by Mike Sokol »
Logged

George Friedman-Jimenez

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 532
  • NYC
Re: freak accident? help!
« Reply #138 on: June 17, 2012, 01:06:23 AM »

Thanks Mike. Might be useful insurance in some of the substandard buildings we play in. By the way, how often would one expect to encounter a RPBG in real life playing clubs in NYC or NJ? I have never heard of anyone around here getting electrocuted or seriously zapped just playing a gig, although the OP's experience is sobering.
Logged

Jonathan Johnson

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3209
  • Southwest Washington (state, not DC)
Re: freak accident? help!
« Reply #139 on: June 17, 2012, 02:10:54 AM »

By the way, how often would one expect to encounter a RPBG in real life playing clubs in NYC or NJ?

I don't know anything about construction practices in NYC, but I would guess you're most likely to find RPBG in anything built before the safety ground conductor was required, which I think was about 1974 (based on limited research).

Probably more likely in an older church (volunteer "electricians") or a converted home (DIY) than in a building that's always been a commercial structure. Of course, electricians can make mistakes just like anybody.

This Wikipedia article on cheater plugs includes a short discussion about audio ground loops.
Logged
Stop confusing the issue with facts and logic!

ProSoundWeb Community

Re: freak accident? help!
« Reply #139 on: June 17, 2012, 02:10:54 AM »


Pages: 1 ... 12 13 [14] 15 16 ... 22   Go Up
 



Site Hosted By Ashdown Technologies, Inc.

Page created in 0.05 seconds with 26 queries.