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Old 09-12-2008, 10:11 PM   #1
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Default A good example of poor grounding

The other day I was laying out a job for my apprentice and told him I wanted grounding bushings installed on the pipe going to the cable tray. He questioned me saying he thought you only had to do that at hospitals and places such as that. Later on that day I was just starting a run of pipe and it touched the cable tray and the 24x24 j-box and it sparked against the tray. What a better example to show him why I always ground the pipe to the tray.

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Old 09-13-2008, 05:11 AM   #2
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Default grounding bushings

Ya Rong i know what you mean ,you are correct every job we go thur the same deal happens ! with the[ grounding bushings ] we must use them every where and the helpers and some new electricians look at us like we never do that what do ya need them for ? we also use on dead ends to cable tray a bonding jumper . always inside motors and transformers and anything rigid that comes in the bottom of most gear. ive only done one hospital job there fun. we use them on control cable raceways also . next the best fun part is the ground conductor attached to the ground bushing we always use the same size ground conductor thats in that raceway to the lug on the ground bushing the inspector says it must be the same size. , but ive been in heated discussions with electricians on that one . some try and use any size that will fit, like cutting a short piece smaller meaning reducen the ground size so it fits in the lug on the ground bushing so its easy to fit into the lug and jumper to the metal can or gear ,and then the inspector flips out makes us put the same size back in and says it must be that ground size in that raceway only and that raceway ground only . nice to see a commercial issue on this site. take care best to ya Rong


Last edited by nick; 09-13-2008 at 05:52 AM. Reason: spelling
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Old 09-20-2008, 08:04 AM   #3
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rong: Don't you mean poor 'bonding' ? Just being a PITA, I get your point. I am an apprentice, and I am all for bushings, bonding-type locknuts at panels and such, etc. So, it was grounded, it just had a sharp edge?

A different example...but poor grounding just the same...

While working as a maintenance electrician in a plant (tool & die mfr.) I was preparing to move a small machine. It is a 208V 3ph buffing lathe. It's mounted to the top of a wooden workbench. It had a bus drop cable run to it.

Here's the kicker (could have been, literally)...

There was also a 4sq box mounted to the side of the bench with two duplex rec., for worklight, etc. The bus drop cable fed directly to the 4sq. with a short piece of cable between it and the machine. Phases A, B, & C were connected to red, black, & white on the cable going to the machine. (White wasn't even re-identified. I like to at least tape it blue, black, or red, something other than white...- some just say I'm anal... I say F**k 'em).

Anyway, the short piece of cable to the machine had the phases connected to the phases of the machine. Great, OK, the machine worked. Problem...or potential deadly problem... The grounding conductor in the short cable wasn't connected to anything. NOTHING. There didn't seem to be a grounding lug in the machine's cast J-box, but at least drill a freakin' hole and install a lug!!!

This is a machine that, due to the wooden bench, was isolated from EVERYTHING, not even remotely indirectly grounded or bonded to ANYTHING!! And to boot, the operators generally lay one of their forearms over the top of the machine to steady their hand as they buff the metal parts being produced. I could just imagine one of the phases touching the metal case, sitting there hot, waiting for a machinist to touch the machine's metal and something that was ACTUALLY grounded. ZAP!! 208 (or 120 to ground) potential, possibly through his heart.

Made me a little sick, and a lot pissed!!

The machine did not get moved until I did my best to provide grounding means in the machine J-box. Real freakin' hard, drill a 1/4in hole, scrape the paint, attach a lug. WOW, difficult! And ACTUALLY use the grounding conductor in the short piece of cable.

Oh... back at the 4sq, the ground from the feeder bus drop cable was being used... as the NEUTRAL (grounded) conductor for the two duplex receptacles, and for the ground of the duplexs... DOH!!!

Even as bad as that is, connecting Ground & Neutral together downstream of the service, the metal 4sq had no connection to the machine, due to the wooden bench, and the plastic-sheathed cable. At the disconnect (plug-in, fused disco on overhead 208/120 busway, the ground from the cable went to the Neutral lug with a jumper or fed straight through to the Ground lug.

This was the case (GND & Neutral bonded together) all through the plant, machines not grounded, white used as a phase conductor, neutral just used as a ground... Most machines that were grounded were grounded to the Neutral lug in the disconnect switch at the overhead busway. (With a jumper installed between the Ground lug and the Neutral lug). ?!?!

Anywhere they wanted to get 120, they would use one phase and ground. It's 120, right??

My only regret for joining the IBEW as an apprentice, is that I didn't stay to correct all the violations and dangerous conditions. I did let management know that the electrical connections were done in dangerous manners at many places in the plant. What more could I do? It would have taken years, possibly, on my own to correct all the screw-ups of 40 or 50 years worth of "Whatever works" ... "Just get it done" ... "Use whatever you can to make it work".

Last edited by BP_redbear; 09-20-2008 at 08:11 AM.
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Old 09-20-2008, 08:30 AM   #4
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I realize the prevoius post was pretty long, I'll keep this one short.

At the same plant, I was looking in a 208/120 CB panel, to figure out what breaker a welder receptacle was connected to. (Incomplete directory - and I wouldn't trust it anyway). I see a 3/4 EMT at the top of the panel with 3 white 10AWG and one red 10AWG ??? WHAT THE...???

The whites were on a 3-pole breaker, A, B, &C phases going to a milling machine. The RED, at the panel, was connected to the Neutral buss, apparently being used as the GROUND for the machine. DOH!!! Whites were not even re-identified, just left white... IDIOTS! Red could have at least been taped GREEN??? (Or would it have been white, cuz it was connected to Neutral??)

I don't recall any of the panels in the plant having a Ground buss. Apparently, all circuits, equipment, and machines were supposed to be connected (grounded/bonded) through EMT, rigid, IMC, flex Greenfield, or some other metal conduit?? I couldn't quite find an answer to that. Where were the equipment ground wires supposed to go?? Was there supposed to be a ground buss installed in the panel on site?

I have many more stories (sad) like this, but I'll stop for today... it was very dangerous being an electrician there, white as an ungrounded phase, black as ground, red as ground, some things not grounded at all, Ground and Neutral bonded everywhere, Ground used as a grounded conductor...
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Old 09-20-2008, 08:49 AM   #5
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Quote:
Originally Posted by Rong View Post
...I wanted grounding bushings installed on the pipe going to the cable tray. He questioned me saying he thought you only had to do that at hospitals and places such as that.
So, you're saying he DIDN'T do what you SAID to do? Or did you agree with him, and tell him "OK, don't install them."?

Maybe he was at least partially correct... are grounding bushings only required at services, and/or where concentric knockouts are used? (I don't intend to argue with someone going above and beyond the NEC 'minimum' requirements.)

quote "...Later on that day I was just starting a run of pipe and it touched the cable tray and the 24x24 j-box and it sparked..."

Why did it spark? Was there potential on the pipe you were running, and/or potential on the tray, or on the J-box? Not sure I understand why it sparked. Was the pipe going to the tray completely isolated, not touching the tray mechanically/electrically/ at all?

Being an apprentice myself, I am not trying to argue or question your judgement, just looking to understand a wirman's reasons. Just keeps us thinking, always learning.
Thanks.
BP

Last edited by BP_redbear; 09-20-2008 at 07:04 PM. Reason: change concentric to eccentric, then back, LOL
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Old 09-26-2008, 07:17 PM   #6
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Quote:
Originally Posted by BP_redbear View Post
So, you're saying he DIDN'T do what you SAID to do? Or did you agree with him, and tell him "OK, don't install them."?

Maybe he was at least partially correct... are grounding bushings only required at services, and/or where concentric knockouts are used? (I don't intend to argue with someone going above and beyond the NEC 'minimum' requirements.)

quote "...Later on that day I was just starting a run of pipe and it touched the cable tray and the 24x24 j-box and it sparked..."

Why did it spark? Was there potential on the pipe you were running, and/or potential on the tray, or on the J-box? Not sure I understand why it sparked. Was the pipe going to the tray completely isolated, not totuching the tray mechanically/electrically/ at all?

Being an apprentice myself, I am not trying to argue or question your judgement, just looking to understand a wirman's reasons. Just keeps us thinking, always learning.
Thanks.
BP

Sorry been away awhile. There were 9 conductors in the cable tray running a high current oven. The pipe I was running was NOT connected to anything as I was just starting the pipe run from the 24x24x12 JB I touched an I beam and the cable tray. The run feeding the oven was over 300' to the MMC cabinet. Simple induction caused the cable tray to pick of stray voltage and not being properly BONDED (grounded) the stray voltage had no were to go.
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Old 09-28-2008, 08:21 PM   #7
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had a call the other day, they had a commercial freezer and refer side by side. they said they would get a shock if they touched them at the same time. what it amounted to was the freezer was 120/208 and the original installer ran a 3 wire circuit to it which meant it was not grounded. ran a 4 wire circuit and made a new cord and all was well. all the original guy would have to do is bond the case and while it wouldnt have been code compliant it would have worked just fine for the life of the unit.

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