Equipment Grounding UNGROUNDED SYSTEM

[romex jockey]

It does, and the section was mentioned earlier. I just means that the installation you mentioned was not compliant.
View attachment 2553790

ok, sure, fine for industrial process, but what of a delta coming into a multi purpose structure? ~RJ~

 

[texie]

ok, sure, fine for industrial process, but what of a delta coming into a multi purpose structure? ~RJ~

That's not likely to happen. The only delta likely to be supplied to almost any building today would be a 4 wire center tapped and grounded service. And even that is getting rare in most places.

 

[hornetd]

Probably not as uncommon as you would think. Take say a 120/208 volt transformer that XO was not bonded, Fault happens on a circuit, now the other two phases are 208 volts to ground, but still 120 volts to neutral. A fault happens on another circuit elsewhere on a different phase, now one or the other, or both breakers trip, but it would be a phase to phase fault, at the higher voltage, not a phase to neutral fault.

A 120/208 volt supply can only come from a wye connected transformer. Doesn't the code require all such transformers to be grounded at their center point?

 

[hillbilly1]

A 120/208 volt supply can only come from a wye connected transformer. Doesn't the code require all such transformers to be grounded at their center point?

Yes, but apparently a lot of “electricians” don’t know that! LOL! I’ve come behind so many that were not, I’ve lost count!

 

[romex jockey]

Yes, but apparently a lot of “electricians” don’t know that! LOL! I’ve come behind so many that were not, I’ve lost count!

i was one myself , but youse guys straightened me out , old 'delta' thread>>>

https://imgur.com/IPNoaIk

https://imgur.com/4Ai7wuS

https://imgur.com/iCXPOOt

i ended up contacting the xformer rep , who informed me to look a tad closer , which revealed X0 not being made into .

A 120/208 volt supply can only come from a wye connected transformer. Doesn't the code require all such transformers to be grounded at their center point?

wouldn't an MBJ exist in any system ? is the grand Q hornetd

~RJ~

 

[MTW]

Ungrounded deltas exist in many places where people install stepdown transformers backwards to feed equipment that does not match the service voltage.

Such as a site that has a center tapped 240V delta service and needs a feeder for some 480V equipment. The 480V winding will be a pure delta, and has no way to ground it, other than make it a corner grounded. They usually know less about corner grounding requirements than they do ungrounded systems.

208 to 480V, 240V to 480V, or 480 to 600V, proper step-up transformers exist, but many times people use the wrong one in reverse because its already on hand or much cheaper to find a used one.
I see it often in the plants that I work in, and never see a ground fault monitoring system.

 

[StarCat]

My concern is that, at least in some of the biological and pharmaceutical laboratories I helped to build or serviced, that they did not have an in house electrician. So what I was trying to do was give them the means to know when they needed to call in the electrical service contractor that they normally turned to. In the research laboratory they had some nasty pathogens under refrigeration. The reason that the Electrical Engineer had specified Delta supply was to avoid interruption of the power to the refrigeration from a single fault. To me the only way that makes sense is to have ground fault detection so that they can act on the fault very promptly. Since they did not have a contract for a regular electrical testing routine as you indicated the first fault could be around long enough for the second fault to occur. To me that doesn't make any sense whatsoever. Which is why I brought that up in the first place. I'm at a loss to figure out why the NEC does not require fault monitoring when the installation is taking advantage of the exception for continuity of service.

About operations like that not having someone qualified " in house." One time in Ft. Worth Texas I was dispatched to Alcon Labs. The supervisor who called me out had " rewired " a walk in freezer which was not bring Evaporator fans on due to loss of charge. He thought he could bring the system back by getting the fans to run. An old Navy guy once told me a little knowledge is a dangerous thing.....
Its because everything has been monetized that organizations make bad decisions, and also this pertains to the cowardice noted above and refusal to call a spade as a spade.

 

[hornetd]

Something that I was going to mention earlier is that sometimes inspectors will prevent these mistakes but not all of them are qualified to do inspections of more complex installations. On one job we installed a fire pump in a hotel but the foreman did not have a Neutral pulled from the Utility's 480/277 Wye connected transformer. Along comes the inspector who was not knowledgeable on fire pumps or on 480 services or; OK I don't read minds. He was smart enough to know he didn't know. He comes back with the Chief Electrical Inspector for the jurisdiction. Then I got the real surprise of that job. At this point I was an apprentice and inspectors held the status of Demigods to me. The chief inspector couldn't see it either. That opened my eyes to the need for me to get as much knowledge as I could because I realized that the foreman, Inspector, and Chief Inspector had all missed the requirement for a neutral to be brought to the Service Disconnecting Means and bonded to the enclosure and the Equipment Grounding Conductor (EGC) from the Fire Pump. Had I been aware of there being only three conductors set up for the pull through plastic conduit I dare to hope that I would have pointed out, Chapter and Verse, that a Neutral; albeit one sized as if it were an EGC, is always required from such Wye connected transformers. I realized then that doing sound work was going to be up to me and even the foreman & inspectors knowledge must be a backup to my doing it right. After that I worked hard to have the material in the apprentice training program down for every class. I may have overdone that a bit because the other apprentices started calling me professor and the instructors stopped calling on me because they assumed I knew the answer which occasionally left me wondering if I really did. Not every instructor was as sharp or thorough as one might hope.