Sheet metal shop coil line apparatus transformer questions

[winnie]

You don't get it, I don't get it. You are asking us to explain the thought process of someone I disagree with.

Jon

 

[hhsting]

You don't get it, I don't get it. You are asking us to explain the thought process of someone I disagree with.

Jon

No I meant NRTL can one have for groups of equipment functioning that’s the previous post question

 

[tom baker]

A drawing from the equipment mfg should be supplied, so the AHJ can see whats being provided, if its separate cabinets, panels etc, needs to be shown and interconnection details

 

[hhsting]

A drawing from the equipment mfg should be supplied, so the AHJ can see whats being provided, if its separate cabinets, panels etc, needs to be shown and interconnection details

You mean Post #12 attachments? Those are equipment mfg no?


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[MTW]

It appears pretty simple to me, but I've encounter this situation many times. Customer acquires a machine built for a voltage other that what they have. They want to use a transformer they have , or buy a used one for cheap, and connect it in reverse. I've seen many do it. They don't realize that the output coil is nearly always a delta coil, and there is no simple way to ground it, other than corner ground it, or leave it ungrounded. Neither do they realize what the implications are of leaving it ungrounded and floating or corner grounding it. From a safety aspect or equipment operational problems or damage that may result from doing so.

A lot of equipment today built as standard, doesn't play nice with an ungrounded or corner grounded supply. Most new equipment with any electronic requires a grounded wye supply to be reliable. Codes and listings aside, if I'm going to do it and accept the liability and support for the equipment, I want it done right. No mater what the buyer, salesman, line assembler, engineer or inspector thinks. I understand the difference and make it proper or I walk.

It seems clear in this case that the vendor selling the equipment, supplied the wrong transformer, and doesn't understand the difference. The machine builder clearly built the thing for a 480V grounded wye, and the machine dealer cobbled on the wrong type transformer to make the sale. And the customers contractor doesn't understand either.

The codes and standards are not a how to manual or a design manual and should not be used as a substitute for knowledge about the system engineering and design. Nor should they be used as a workaround, to get past inspectors, engineers or designers that aren't fully up to speed with the situation at hand.

This job needs the correct transformer, bonded and grounded properly, and that can't happen with what the vendor supplied. Simple.

 

[hhsting]

It appears pretty simple to me, but I've encounter this situation many times. Customer acquires a machine built for a voltage other that what they have. They want to use a transformer they have , or buy a used one for cheap, and connect it in reverse. I've seen many do it. They don't realize that the output coil is nearly always a delta coil, and there is no simple way to ground it, other than corner ground it, or leave it ungrounded. Neither do they realize what the implications are of leaving it ungrounded and floating or corner grounding it. From a safety aspect or equipment operational problems or damage that may result from doing so.

A lot of equipment today built as standard, doesn't play nice with an ungrounded or corner grounded supply. Most new equipment with any electronic requires a grounded wye supply to be reliable. Codes and listings aside, if I'm going to do it and accept the liability and support for the equipment, I want it done right. No mater what the buyer, salesman, line assembler, engineer or inspector thinks. I understand the difference and make it proper or I walk.

It seems clear in this case that the vendor selling the equipment, supplied the wrong transformer, and doesn't understand the difference. The machine builder clearly built the thing for a 480V grounded wye, and the machine dealer cobbled on the wrong type transformer to make the sale. And the customers contractor doesn't understand either.

The codes and standards are not a how to manual or a design manual and should not be used as a substitute for knowledge about the system engineering and design. Nor should they be used as a workaround, to get past inspectors, engineers or designers that aren't fully up to speed with the situation at hand.

This job needs the correct transformer, bonded and grounded properly, and that can't happen with what the vendor supplied. Simple.

Will ask the engineer to provide datasheet for coil machine see if it’s 480V delta or 480V wye. If it turns out 480V wye then your right but 480 delta then it’s different story. Won’t be long time till I can do this.


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[texie]

Will ask the engineer to provide datasheet for coil machine see if it’s 480V delta or 480V wye. If it turns out 480V wye then your right but 480 delta then it’s different story. Won’t be long time till I can do this.


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I don't think you are fully understanding the discussion. The issue is not that the machine is delta or Y but rather whether the power source supplying the machine is delta or Y. The vast majority of equipment today expects to be supplied from a grounded Y system. In some cases it is critical but in almost all cases it is desired for a number of reasons.
I think MTW summed it up well.

 

[hhsting]

I don't think you are fully understanding the discussion. The issue is not that the machine is delta or Y but rather whether the power source supplying the machine is delta or Y. The vast majority of equipment today expects to be supplied from a grounded Y system. In some cases it is critical but in almost all cases it is desired for a number of reasons.
I think MTW summed it up well.

huh? If the engineer gives me machine manufacturer data sheet that says machine accepts 480V delta then what’s the problem? It’s per manufacturer instruction 110.3(B). Otherwise if the manufacturer datasheet indicates 480V grounded wye then it’s clear need to change. I am mostly code enforcer Not designer so I can’t tell them to change otherwise if it’s like design decision. Note engineer can again come back with what he had originally its premise wiring as well. Why the engineer provide that’s all.

It does have control cabinet secondary of that transformer. Are you saying that wye system is must for control cabinets? Other than that if not then you maybe right I don’t get it. Can you please care to explain or elaborate please?

 

[winnie]

Side discussion about delta vs wye:

A grounded wye source has the benefit that all of the phase conductors are 'balanced' relative to ground. _Some_ loads require this balance. Good examples are most VFDs. Note however that this requirement is set by ground referenced transient voltage suppression devices, _not_ the load itself.

A delta source cannot be grounded in a balanced fashion. It will either be high leg grounded or corner grounded. Many loads will work just fine with a delta source. Good examples are common induction motors. It doesn't matter if the motor is internally wye or delta, simply that nothing in the motor is ground referenced and the only thing the motor cares about is line-line voltage.

In the past, if the manufacturer did not specify a grounded wye source, then you could use anything. These days I believe that the assumption is a grounded wye source, and I would not use another type of source unless specifically permitted by the manufacturer. But as noted many loads will work fine with delta sources .

-Jon

 

[MTW]

I would bet a dime to a dollar that, a machine that unrolls four coils of steel and folds them up into duct work, will have some VFD's for speed and control, along with a computer to synchronize them. I'm not a betting man either, not once in my life.

 

[hhsting]

....[/b] unless specifically permitted by the manufacturer[/b]. But as noted many loads will work fine with delta sources .

-Jon

Please see above part. If I get manufacturer datasheet of the machine and control cabinet indicating delta is ok or Not ok would that not be same as manufacturer permitting? If not then what does it mean manufacturer is permitting and how verifies it.

 

[MTW]

Will ask the engineer to provide datasheet for coil machine see if it’s 480V delta or 480V wye. If it turns out 480V wye then your right but 480 delta then it’s different story. Won’t be long time till I can do this.

Better would be to ask if the equipment can function reliably on a corner grounded 480V delta system, as that's the only way your transformer output can be grounded. I would ask for it in writing.

 

[hhsting]

Better would be to ask if the equipment can function reliably on a corner grounded 480V delta system, as that's the only way your transformer output can be grounded. I would ask for it in writing.

Ask who manufacturer or engineer?

 

[MTW]

Iowa Precision, or the entinty responsible for the design and building of the machine. Not the sales force that sold the thing.
They will be the responsible party if it let's the smoke out, until they find out it was incorrectly supplied.

 

[winnie]

If I get manufacturer datasheet of the machine and control cabinet indicating delta is ok or Not ok would that not be same as manufacturer permitting?

IMHO a data sheet specifying supply is sufficient.

MTW makes a very good point, the question is not wye or delta, but rather grounding. Can the machine operate correctly with imbalanced grounding?

A delta supply implies imbalanced grounding, which is why the two issues are connected.

Jon

 

[hhsting]

Better would be to ask if the equipment can function reliably on a corner grounded 480V delta system, as that's the only way your transformer output can be grounded. I would ask for it in writing.

In addition Would it also be better to ask to manufacturer leaving it ungrounded equipment function reliably also?

 

[winnie]

In addition Would it also be better to ask to manufacturer leaving it ungrounded equipment function reliably also?

With a delta, your possibilities are:

1) corner grounded
2) high leg grounded if your transformer has a center tap on one of the secondary coils
3) ungrounded

The drawings you posted suggested an ungrounded supply, but did not have ground fault detection.

It is worth asking the manufacturer if the ungrounded connection is acceptable, because that is what the supplier drawings show. However IMHO the ungrounded setup is a bad idea for numerous reasons.

-Jon

 

[hhsting]

With a delta, your possibilities are:

1) corner grounded
2) high leg grounded if your transformer has a center tap on one of the secondary coils
3) ungrounded

The drawings you posted suggested an ungrounded supply, but did not have ground fault detection.

It is worth asking the manufacturer if the ungrounded connection is acceptable, because that is what the supplier drawings show. However IMHO the ungrounded setup is a bad idea for numerous reasons.

-Jon

Why not just ask the manufacturer if they provided the wiring because if it turns out it’s NOT premise wiring then NEC 2014 250.20 would not apply. Correct so not much you can do but have ground fault detection etc however it is premise wiring then yes it needs to be grounded?

 

[MTW]

Ungrounded is bad for VFD drives, they retire an equal-potential ground reference as well as other equipment, it leads to transient voltages on the equipment, especially when a fault happens on the equipment. The NEC requires that for an ungrounded systems you must install a ground fault detection system, and have trained staff on hand that is qualified in these systems and that they are knowledgeable about detecting and locating a fault. These issues were mentioned by others earlier

The simplest, cheapest, most trouble free solution has already been given. And if you could educate the vendor what they supplied is not the correct solution, they will likely not do it to the next guy.

 

[MTW]

Will ask the engineer to provide datasheet for coil machine see if it’s 480V delta or 480V wye. If it turns out 480V wye then your right but 480 delta then it’s different story. Won’t be long time till I can do this.

Is the forum worthy of a response? Did they tell you to leave it ungrounded as shown in their print, and call it NRTL listed?

Or did they tell you they shipped the wrong transformer and connection drawing? Curious minds would like to know...