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Author Topic: Too isolated ground  (Read 17780 times)

Jonathan Johnson

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Re: Too isolated ground
« Reply #20 on: November 27, 2013, 08:01:36 pm »

So what I see in the photo is a floating neutral. If iso ground must be maintained past the transformer, the neutral of the secondary (marked XO, which I assume means "crossover" for the neutral taps of the secondaries, and therefore is a neutral bus of some sort) should have a separate ground running back to the service entrance. In this case, the chassis of the transformer is grounded, so it's not really ISO ground at that point. To avoid the floating neutral it should be bonded to ground.

Is there a good reason for the floating neutral in this installation?
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John Roberts {JR}

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Re: Too isolated ground
« Reply #21 on: November 27, 2013, 09:07:28 pm »

there is way too much to type regarding the XO so i will post a simple reply. the xo is where you get your neutral from a transformer. the xo must be grounded. the xo in the foto has a white circle around it. i'm not trying to be a smart alec but if you really want to learn about the technical aspects of all this electrical engineering school is a must.

i have never had gfic recepticals specified for use on an iso circut. there are special recepticals that you must use. the ground hole will have a green dot next to it. the metal frame of the receptical is not connected to the ground hole.

Thanks, I already have a pretty good handle on how the electrons behave just trying to get up to speed with the jargon..

So it is as I speculated, XO is the center-tap of the transformer. Since this gets connected to neutral with a low impedance path (I ASSume it;s low impedance), connecting the isolated ground there should be adequate to trip breakers in case of a mains fault to that ground.

I imagine there could be a subtle voltage difference between the transformer center tap and neutral at the panel, depending on balance of the two legs, and impedance of that short(?) connection path. 
 
Happy Thanksgiving folks...

JR
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Craig Hauber

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Re: Too isolated ground
« Reply #22 on: November 27, 2013, 09:22:21 pm »

the nut is crossthreaded !!! that iso ground wire jod is B.S. ! the ground wire should have two 1 hole straps holding it to the wall. the wire is too long and a tripping hazzard. all i see is yellow tape on the black ground wire. yellow tape is what you mark C leg on a 277/480 or C leg on a 3 wire 480 system with. when the iso ground wire is black you put GREEN and YELLOW tape on both ends. this is some more B.S. work done by idiot jerk offs that take a class to learn the answers so they can get a journeyman card but dont know SHEEET !

I thought there was 5 yrs of apprentice before you could get a journeyman's card?  (What state allows you to get a card with just a test?)
And where's the card-carrying master on the jobsite that should be verifying everything the journeymen are doing?  (It would be like the crew chief going awol and letting the roadies set up the PA unsupervised)

Finally, if it was so wrong, you should be sending all this to whoever is in charge of the state electrical inspector that approved the end result, (along with a cc to the engineers for the job)

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I fired every guy that had a journeyman card. some didnt even know what a bender or a fish tape was

I've worked with some very good electricians that do nothing but residential,  they can't remember the last time they've had to touch either of those tools either.  The fault lies more in who assigned them on that job (like sending your monitor engineer to run the video switcher)
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Kevin Hoober

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Re: Too isolated ground
« Reply #23 on: November 27, 2013, 10:11:08 pm »

Is there a good reason for the floating neutral in this installation?

No, this is a typical dedicated A/V panel in an installation.  There are some odd industrial applications where the center tapped secondary is not grounded, but this ain't it!

I suspect the contractor misunderstands the concept of iso-ground.

Kevin H.

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Jeff Bankston

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Re: Too isolated ground
« Reply #24 on: November 28, 2013, 04:16:29 am »

I thought there was 5 yrs of apprentice before you could get a journeyman's card?  (What state allows you to get a card with just a test?)
And where's the card-carrying master on the jobsite that should be verifying everything the journeymen are doing?  (It would be like the crew chief going awol and letting the roadies set up the PA unsupervised)

Finally, if it was so wrong, you should be sending all this to whoever is in charge of the state electrical inspector that approved the end result, (along with a cc to the engineers for the job)

I've worked with some very good electricians that do nothing but residential,  they can't remember the last time they've had to touch either of those tools either.  The fault lies more in who assigned them on that job (like sending your monitor engineer to run the video switcher)
first of all 5 years dont mean a thing. i'v had guys on my crew that were 8 year helpers because no one has the time to train them. most companies will get one journeyman to run a crew of helpers and apprentices. thank the illegal aliens that infiltrated the construction trade and drove the bidding down. you dont need a card carrying master on the job in california. when california passed the journeyman card requirement you had to have 8600 hours of on the job experience to qualify to take the test. the hours were not checked when i took the test, they went by the honor system. all you had to do was take a weekend class that taught you the answers to the test. thats right a state approved class that cost about 200 bucks to teach you the answers. all you had to do was memorize the questions and multiple choice answers and you could pass the test. after you took the class you could take the test any time you wanted. also ,you didnt have to take the class but if you wanted to pass you needed to. there was lots of questions on the test that had(has) nothing to do with what we do in the field and some were not even about electrical. i took the class and told the teacher the whole thing was a bunch of b.s. and he agreed. anyone could fill out the online application, type in the 8600 or more hour requirement and no one ever asked to see w-2 forms or check to see that you actully worked as an electrician. then you took the class and learned the answers. then you made an apointment and on the date you went to a building and took the mulitple choice test on a computer. if you passed you paid $300.00 and got your journeyman card good for 3 years. as for reporting fraud, the system was(is) such a beauracratic nightmare that it was impossible to report fraud. also there were no questions on the test about wiring up a transformer. i came up with a 100 question and diagram test for those that "claimed" to be a journeyman or had a card. it was a fill in the blank test and i had a drawing of h1 h2 h3 x1 x2 x3 xo and the applicant had to draw the wires with a pencil and label the color code and where they terminated. i eventually stopped working for others due to this B.S.. another electrician friend did likewise. i have told friends if they need a big job done i have 2 electrical contractors that only hire competent workers. if my boss will only send me helpers when i need journeyman i can either work with what i get or quit. its the foremans job(mine) to see the job gets done right. i would always end up putting in the switch gear and terminating the connections. i couldnt train anyne because i always had a skeleton crew like everyone else. like i typed i got tired of the bs and quit. btw some years ago i worked with an electrician that was a master electrician, the guy didnt know sheeet ! just cause they got a card dont mean nothin to me.

also, residental electricians were forbidden from applying for a journeyman. it was for commercial electrical electricians only. iirc several years ago if you were just starting out in the electrical trade you had to be enrolled in an electrical school before you could work in the field.

industry definition of a journeyman electrician > an electrician that can take a set of plans and do the entire job without having to seek instruction from other electricians. this excludes rfi's that pertains to errrors or misprints on plans or extras. a foreman is a journeyman electrician that can also direct/lead/manage/supervise a crew.
« Last Edit: November 28, 2013, 05:06:59 am by Jeff Harrell »
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Stephen Swaffer

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Re: Too isolated ground
« Reply #25 on: November 28, 2013, 11:02:21 am »

Jeff, I'll take your word for it that your electrical work is top notch-and I assume you put far more effort into your electrical classes than you did English.  I have been an industrial electrician for 16 years-much of it in the same factory.  It can be really humbling when you go back to a job you did 5 years earlier and realize that you did something that you now understand was really, really silly-been there before.  I have been a licensed master electrician and contractor for 12 years(fairly and honestly passed the Experior journeyman and master exams with 94% or better on the first try)-and I still have a lot to learn in the electrical world. (By the way master electrician=one that can draw the plans.)  I always try to find continuing ed classes that not only meet relicensing requirements but also challenge me to learn more.

I suspect that the XO-neutral-bonding question is a matter of local preference.  Iowa has only had a state program for 6 years-as yet there is very little politics on the inspection side of things and they can only enforce the NEC as written.  On a separately derived system-ie transformer supplied panel-the NEC requires the neutral to be bonded to the ground in ONE place.  This can either be the X0 bonded to the ground in the transformer-probably the most  common because it is usually the easiest-or alternatively the neutral buss can be bonded in the panel-if they are not connected in the transformer. My inspector always checks to see that one-and only one of the bonding connections is there.  The NEC does give the AHJ (authority having jurisdiction) final say-so it may be that your inspectors have decided for consistency to require bonding in the transformer and never allowing it in the panel.  There would be advantages to that from an inspection standpoint and future work standpoint when multiple inspectors and electricians are involved.  From a technical and safety standpoint the important thing is that one bonding point does in fact exist.
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Steve Swaffer

Rob Spence

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Re: Too isolated ground
« Reply #26 on: November 28, 2013, 09:00:26 pm »

In my state, the only difference between journeyman and master is that masters can hire employees (hence they need more business education) but have the same electrical education requirement.
So, a journeyman can be a sole proprietor and pull permits and do work but cannot have employees.
This is in my state. Your state may vary.

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Samuel Rees

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Re: Too isolated ground
« Reply #27 on: April 30, 2014, 07:20:36 pm »

 Isn't the "safety" aspect defeated if ground isn't an alternative path to neutral? Electrical noob here... Be nice... I'm just sure I'm not the only one with this question.
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Cailen Waddell

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Re: Too isolated ground
« Reply #28 on: April 30, 2014, 08:43:27 pm »


Isn't the "safety" aspect defeated if ground isn't an alternative path to neutral? Electrical noob here... Be nice... I'm just sure I'm not the only one with this question.

Yes. The purpose of a ground is to provide an alternative path for a fault current back to the neutral/ground, etc. If there is not a ground neutral bond then the breaker would most likely not trip.

I'm not an electrician, but I had to learn a lot about it to keep the electricians on the facilities we build from screwing it up.
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Jeff Bankston

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Re: Too isolated ground
« Reply #29 on: April 30, 2014, 08:55:35 pm »

well let me explian this hole "master" think to ya'll. i have a masters license in baiting. i work on a boat fishing in the water.(where else would you fish ?). i started out as a junior baiter and finally pasted the master baiter test. so i am proud to say i am a master baiter.
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Re: Too isolated ground
« Reply #29 on: April 30, 2014, 08:55:35 pm »


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