ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1] 2 3   Go Down

Author Topic: A fun contest  (Read 2096 times)

Peter A Viehoever

  • Newbie
  • *
  • Offline Offline
  • Posts: 9
A fun contest
« on: July 12, 2020, 10:58:03 pm »

Except there is no prize and it doesn't have to do with sound. It's pretty quiet these days and I was curious to see what you think.

Several years ago a friend got a new water storage tank and treatment system put in next to their well. The system installer only found 240vac at the well and the treatment equipment required 120. To get 120 he used one hot leg and directed the neutral into a ground rod next to the equipment. Unfortunately, it worked. Fortunately, nobody got hurt.

As I recall, I was creeped out and replaced that arrangement with a transformer. I had a hard time explaining to the homeowner why it was a bad idea to use the ground rod for the neutral.

The contest (remember, no prize except the joy of clarity) - What is the best two or three sentence explanation for a non-technical person so they understand the reason for not using the ground rod to get 120? Or other, as you see fit.

Thanks,

Peter
Logged

Caleb Dueck

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1311
Re: A fun contest
« Reply #1 on: July 13, 2020, 12:14:41 am »

Except there is no prize and it doesn't have to do with sound. It's pretty quiet these days and I was curious to see what you think.

Several years ago a friend got a new water storage tank and treatment system put in next to their well. The system installer only found 240vac at the well and the treatment equipment required 120. To get 120 he used one hot leg and directed the neutral into a ground rod next to the equipment. Unfortunately, it worked. Fortunately, nobody got hurt.

As I recall, I was creeped out and replaced that arrangement with a transformer. I had a hard time explaining to the homeowner why it was a bad idea to use the ground rod for the neutral.

The contest (remember, no prize except the joy of clarity) - What is the best two or three sentence explanation for a non-technical person so they understand the reason for not using the ground rod to get 120? Or other, as you see fit.

Thanks,

Peter

It's against code, only bond neutral/ground at service entrance.  May also be dangerous, and introduces ground loops. 

Oh, and the worms.  Think of the poor toasty worms.
Logged
Experience is something you get right after you need it.

Erik Jerde

  • Classic LAB
  • Hero Member
  • *
  • Offline Offline
  • Posts: 1018
Re: A fun contest
« Reply #2 on: July 13, 2020, 11:12:39 am »

Except there is no prize and it doesn't have to do with sound. It's pretty quiet these days and I was curious to see what you think.

Several years ago a friend got a new water storage tank and treatment system put in next to their well. The system installer only found 240vac at the well and the treatment equipment required 120. To get 120 he used one hot leg and directed the neutral into a ground rod next to the equipment. Unfortunately, it worked. Fortunately, nobody got hurt.

As I recall, I was creeped out and replaced that arrangement with a transformer. I had a hard time explaining to the homeowner why it was a bad idea to use the ground rod for the neutral.

The contest (remember, no prize except the joy of clarity) - What is the best two or three sentence explanation for a non-technical person so they understand the reason for not using the ground rod to get 120? Or other, as you see fit.

Thanks,

Peter

Was there something there that required 240?  If not I can solve that problem with some white tape and re-landing one of the wires in the panel.  Code compliant and a helluva lot easier.
Logged

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 16639
  • Hickory, Mississippi, USA
    • Resotune
Re: A fun contest
« Reply #3 on: July 13, 2020, 12:18:21 pm »

Several but because it's wrong is a good one.

Grabbing neutral from an earth ground path is not guaranteed to be a low resistance bond. During a high current fault the resistance could prevent a fuse/breaker from tripping open. 

Presumably the equipment safety ground is now bootlegged to that questionable pseudo neutral.  In even normal operation that safety ground will likely experience a voltage potential. During a high current fault that voltage could rise dangerously. 

When in doubt do what's right... 8)

JR
Logged
When in doubt do what's right.

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2382
Re: A fun contest
« Reply #4 on: July 13, 2020, 12:48:12 pm »

Was the ground rod connected via metallic path back to the service-in technical terms, was there an equipment grounding conductor?  If not, this installation still is unsafe.  Why?

Assume there is a 20 amp breaker on the service. Also assume the ground rod meets code (a single rod might not), which requires max of 25 ohms resistance.  Ohms law says it will take 500 volts to force enough current through the breaker to trip it, if the motor shorts out (energizing it's frame).  Since we are dealing with 120 volts to ground, your ground road, plus the resistance of the ground rod at the service (which would be in series so they add) must be less than 6 ohms to trip the breaker should a fault occur.  The numbers are obviously worse if it is a 30 amp breaker.

As JR points out, if the EGC exists, there is potential for a voltage potential to exist which can be dangerous in the event of a bad connection. (seen plenty of those).

Then there is the code requirement that EGC's must be identified as such (green, green with yellow stripe, or bare)-and if identified as such cannot be used as grounded (neutral) conductors.  If I am working in a panel (or any junction between the panel and the load) and I assume that the EGC marked wires in a panel are in fact EGC's and temporarily remove one, it can become energized if connected to a load like a transformer-making a hazardous situation for the electrician.
Logged
Steve Swaffer

Rob Spence

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3484
  • Boston Metro North/West
    • Lynx Audio Services
Re: A fun contest
« Reply #5 on: July 14, 2020, 09:15:08 pm »

Was there something there that required 240?  If not I can solve that problem with some white tape and re-landing one of the wires in the panel.  Code compliant and a helluva lot easier.

In the US, submersible well pumps use 240v.
Logged
rob at lynxaudioservices dot com

Dealer for: AKG, Allen & Heath, Ashley, Astatic, Audix, Blue Microphones, CAD, Chauvet, Community, Countryman, Crown, DBX, Electro-Voice, FBT, Furman, Heil, Horizon, Intellistage, JBL, Lab Gruppen, Mid Atlantic, On Stage Stands, Pelican, Peterson Tuners, Presonus, ProCo, QSC, Radial, RCF, Sennheiser, Shure, SKB, Soundcraft, TC Electronics, Telex, Whirlwind and others

Frank Koenig

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1083
Re: A fun contest
« Reply #6 on: July 14, 2020, 11:17:49 pm »

In the US, submersible well pumps use 240v.

Indeed. And in the "good old days" it would have been perfectly normal for exactly two wires to be strung from the main house, or wherever the power came from, to the well house, usually supported on little ceramic knobs with lag-screw-like studs screwed into any available trees. This actually is not all that bad as the well pump has a pretty good local earth ground, by virtue of being down a well,  and the buildings were far enough apart so that you couldn't touch both of them at once.

As for the contest, I shall not participate as "draw the damn circuit" is not the answer you're looking for :)

--Frank
Logged
"Nature abhors a vacuum tube." -- John Pierce, Bell Labs

Kevin Graf

  • Sr. Member
  • ****
  • Online Online
  • Posts: 333
Re: A fun contest
« Reply #7 on: July 15, 2020, 08:06:16 am »

Was the water pipe from the well to the house metal?
Logged
Speedskater

Dave Garoutte

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2287
  • San Rafael, CA
Re: A fun contest
« Reply #8 on: July 15, 2020, 12:22:57 pm »

Was the water pipe from the well to the house metal?
No, but the bucket was.
Logged
Nothing can be made idiot-proof; only idiot resistant.

Events.  Stage, PA, Lighting and Backline rentals.
Chauvet dealer.  Home of the Angler.
Inventor.  And now, Streaming Video!

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2382
Re: A fun contest
« Reply #9 on: July 15, 2020, 12:55:10 pm »

Indeed. And in the "good old days" it would have been perfectly normal for exactly two wires to be strung from the main house, or wherever the power came from, to the well house, usually supported on little ceramic knobs with lag-screw-like studs screwed into any available trees. This actually is not all that bad as the well pump has a pretty good local earth ground, by virtue of being down a well,  and the buildings were far enough apart so that you couldn't touch both of them at once.

As for the contest, I shall not participate as "draw the damn circuit" is not the answer you're looking for :)

--Frank

Pretty sure this lake and whatever energized it probably had a pretty good local earth ground as well.

https://www.foxnews.com/us/arizona-lake-electrocution-incident-lake-pleasant-scorpion-bay-brothers-killed-boat-dock
Logged
Steve Swaffer

ProSoundWeb Community

Re: A fun contest
« Reply #9 on: July 15, 2020, 12:55:10 pm »


Pages: [1] 2 3   Go Up
 



Page created in 0.026 seconds with 22 queries.