4 of 7 Grounded Versus Ungrounded System, NEC 2014 - [100], (35min:35sec)

[@adambachert9405]

I work in an old steel mill and we have mostly ungrounded systems anywhere there is 3 phase. The diagram you used shows an EGC run with current carrying conductors even for the ungrounded system. What is the purpose of the EGC in an ungrounded system if there's a separate equipment ground with a grounding electrode at each of the devices in the circuit?

[@MikeHoltNEC]

To open the circuit in the event of a second ground fault from a different phase.

[@charletonzimmerman4205]

The reason, that old steel mill, has a "Delta" ungrounded, system is the Over head cranes, with wound rotors on the Hoist, before VFD, cranes used that, for lifting "Ladles", of molten steel, also the "Arc Furnace", has 3 electrodes, for melting, that creates, all sorts of back, feed Induced currents, on building steel. They should have detector/lamps, & ground leakage, meters that you should be "Monitoring", but I bet, the Management, doesn't.

[@ianshay2664]

EE here, can confirm, focused entirely on electronics, and power (three phase, delta, wye, grounding, etc.) was one chapter of one semester

[@coldfinger459sub0]

I was in a very old warehouse with a ungrounded system installing HVAC equipment seven years ago. Unfortunately a residential electrician was hired to wire up this commercial three phase building. He knew he wasn’t qualified and I knew he wasn’t qualified but he did a lot of research and both of us watch Mike Holt videos. And many others. End of story he added too large transformers three face for 277 208 and 120 and 240 legs ( I am not Electrician my background was an automotive technician Electronics drivability electrical and air-conditioning) He explained it to me this ungrounded building and corner grounding his new transformers that he was installing. When they tore up the concrete for some other work next to the transformers he bonded the corner grounding electrode from the transformers to the re-Barb of the building and he drove a ground steak and bonded to the wires together and he had me Silverbreeze the wires to the re-Barb and all his connections that we’re going to be buried underground in the concrete so there would be no corrosion with good electrical conduction. ( HVAC technicians you silver for braising and I use 95% silver on all these ground electrode to the six gauge wire. ) Flash forward six or seven years to this year a new electrician came in to install some new rooms and equipment and all of a sudden electronics around the building started burning up or having glitches in malfunctioning. One of my particular air handler‘s in one room started burning up motors ECM. Several circuit boards burnt up just on this one air handler. Then I took it to a extreme and completely gut it out the air handler and replace every electronic device in the air handler and it immediately burnt up another circuitboard within two days. The owner of the building told me he had a good qualified electrician do all the work when I told him I thought it was a ground problem some sort a voltage problem causing this problem. Approaching the end I got very pissed off because I replace so many circuitboard so many ECM motors in this very complicated LG multi-VRF refrigerant system continuously kept shutting down and having glitches. So I found the circuit board that I originally recommend a transient and voltage spike surge protector that was installed many years ago and I opened up the panel. I went over to the other panel and disconnected the wires from the circuit breaker to my air handler that kept burning out motors and circuit boards. I got 100 foot Home Depot 10 gauge extension cord and stripped both ends off. I wired up a new circuit breaker to the other panel I knew the electrician did not touch with a extension cord dangling out of the front of the panel definitely not electrical or OSHA approved using 120 V extension cord to run 208 voltage. And I ran that extension cord all the way to the back room disconnected my air handler and hooked it up to this extension cord. Problem solved no more burning up ECM motors no more burning up circuit Circuit boards and no more blowing fuses every couple days while trying to track down the problem. I proved my point and the owner of the building had the electrician run a new conduit with a separate line from where I connected to that one air handler to take care of the problem but he still had 100 either electrical problems caused by the last electrician that I am not going to go after and tackle. (i’m just an automotive technician a grease monkey I change oil and rotate tires) In nearly every HVAC job I go to and every three phase commercial building I continuously run into these problems with electricians that are nothing more than wire monkeys who can blow holes in walls been conduit and pull wires but haven’t the slightest inkling of the basics of how electron flow works and even fewer know how to even properly wire up motors and understand readings. But then again I’m just a grease monkey what do I know

[@vamnews]

Thanks for the clear explanations of grounded and ungrounded.

[@fishtailfred8686]

Excellent discussion!

[@bretgreen5314]

Really good information. Thank you Mr. Holt and team. . .

[@shawnmuench]

Ok good- 9:40 answered my question from the grounding myths video: whether grounding saves lives or not. It saves equipment, not lives! Is what I gather. Old school thinking on this will say it saves lives because of the electricity being "redirected to ground" but you can just as well provide that path as a human body, so that's a bad supposition. Can anyone weigh in more on this for me?

[@tylerfabish5578]

Your supposition is correct. The idea is the ground provides a path back to transformer neutral to cause an overcurrent event and trip the breaker to kill the power. Happens in just a few 1/60ths of a second in the USA (60hz power), and depending on the breaker installed. The type of breaker required to save a human is a GFCI breaker. A standard breaker won't because the amperage required to kill you is very small. Remember, amperage (current) is what kills, not voltage, but a bigger voltage makes it easier to push more amps through your skin. So you can short out the system with your body but as long as current stays below the breaker rating, the power won't cut out and you will continue to be shocked until you break contact. A GFCI detects the difference between hot and neutral current. Think: power in vs power out. They are set to detect extremely small differences in current for the purposes of saving a human. Whenthe breaker senses that difference it opens the circuit. - union electrician

[@shawnmuench]

And then I'm like.. whatever ground rod you use I'd suppose it would have to be lower resistance than the water pipe coming into the building right? Or you're inadvertently sending your entire ground system over to that pipe. lots to think about with this stuff and I can see how people make errors related to this.

[@BrunoZanardii]

Hello Mike, I work with locomotives but I don’t know if all concepts shown in your video applies to vehicles as well. Could you please advise?

[@MikeHoltNEC]

Electricity is 'physics' and physics always applies.

[@microcolonel]

My understanding is that locomotives have a chassis ground, like cars.... and locomotives are covered in exposed metal parts.

[@johnnymalicoat754]

They use ungrounded delta on navy ships.

[@charletonzimmerman4205]

You correct, I was an Electrician Mate, fixed many, a Residential Shipyard worker, grounding a panel leg, on a Delta Panel, boy the Paint would, burn, were the panel was mounted to the "Bulkhead".

[@garbo8962]

Back in the early 1980's we had about 20 VFD'S for 2 to 10 HP motors. Had to install a 480 to 240 ungrounded isolation transformer to each drive. Tech told us the drives could not handle a large fault current and I thought this was dangerous not grounding the secondary of any transformer over 100 VA.

[@MikeHoltNEC]

Ungrounded systems installed per the NEC are perfectly Code compliant.

[@vics9830]

I was at an Apt building in the swimming pool that was surrounded by a iron fence I jumped out of a pool and grabbed the fence and got shocked it took all my strength to let go I think the system around that area what ever it was powering should be ungrounded by the swimming pools.

[@nlee5034]

Why isn’t it called “ungrounding system”? Aside from that not fitting the “tense of a word”. But when emphasizing “grounded v grounding”… this label contradicts the definition of “grounding/grounded”.

[@MikeHoltNEC]

It is an ungrounded system.

[@DanBurgaud]

7:58 ... so instead of one electrocuted guy (with the other calling 911), now you got TWO electrocuted guys with no one calling 911...

[@dero5466]

Yeah but still less likely for 2 people to get shocked versus just one

[@BobbaFett312]

the reason engineers in 1950s were better is cause they had to study less, EE field was much smaller back then. right now EE field is exponentially bigger than what it was in 1950s. you cant learn all of that in school