Delta / Wye Step Up Transformer

[LOCILOP]

If you have a primary Delta 208/ secondary Wye 277/480 step up transformer, but there will be no neutral on the secondary wye side. What do you do with the HO terminal on the secondary side?

The ultimate questions is what do I do with the ground(green) wires coming from secondary side?
Do the ground(green) wires have to go to the HO terminal or do they go to the chassis only?

 

[augie47]

Welcome !
Since you are not required to use HO by 250.20(B) you can make it an ungrounded system and bond your ground to the chasis. If you elect to do so, you need Ground Detectors per 250.21(B)
OR you can use HO and establish a ground following 250.30.

 

[iwire]

If you have a primary Delta 208/ secondary Wye 277/480 step up transformer, but there will be no neutral on the secondary wye side. What do you do with the HO terminal on the secondary side?

The ultimate questions is what do I do with the ground(green) wires coming from secondary side?
Do the ground(green) wires have to go to the HO terminal or do they go to the chassis only?

I would hook this up exactly like if you needed the neutral.

Bond the HO to the case and a grounding electrode system.

Your EGCs (green wire) will connect to the bonding point.

 

[infinity]

If you have a primary Delta 208/ secondary Wye 277/480 step up transformer, but there will be no neutral on the secondary wye side. What do you do with the HO terminal on the secondary side?

The ultimate questions is what do I do with the ground(green) wires coming from secondary side?
Do the ground(green) wires have to go to the HO terminal or do they go to the chassis only?

Do you need to use this as an ungrounded system?

 

[iwire]

Do you need to use this as an ungrounded system?

If so a delta / delta seems like a more obvious choice.

 

[LOCILOP]

Delta/Wye Step Up Transformer

Delta/Wye Step Up Transformer

Do you need to use this as an ungrounded system?

No. It's not needed as a ungrounded system. Its new equipment and we know it should have a ground, it's just knowing what to do with the grounds, in the Transformer we are trying to figure out.

 

[templdl]

I would hook this up exactly like if you needed the neutral.

Bond the HO to the case and a grounding electrode system.

Your EGCs (green wire) will connect to the bonding point.

I second that emotion.
As I wire suggested a 480y/277 if left ungrounded will have 480 to ground should on phase goes to ground. The, how would you trip an OCPD? By doing what I war suggest you will have 277v to ground for line to ground insulation purposes. Should a line go to ground and the X0 is grounded now you have a path back to the OCPD causing it to trip which you did have before.
As a side note this can also influence the rating of the OCPD in that they would be 277/480 or 480v rated, the 277/480 are commonly less expensive. They also may be smaller in size which influences the panel size and price.

 

[LOCILOP]

Delta/Wye Step Up Transformer

Delta/Wye Step Up Transformer

Welcome !
Since you are not required to use HO by 250.20(B) you can make it an ungrounded system and bond your ground to the chasis. If you elect to do so, you need Ground Detectors per 250.21(B)
OR you can use HO and establish a ground following 250.30.

Thank You. I will look this up in the code and see if NYC has any amendments to this.

 

[hurk27]

No. It's not needed as a ungrounded system. Its new equipment and we know it should have a ground, it's just knowing what to do with the grounds, in the Transformer we are trying to figure out.

If this transformer will be feeding any VFD drives keep in mind that many VFDs do not like an ungrounded system, if an ungrounded system is not needed then bond the X0 to the case and run your EGC's from there to your disconnect or panel, you can also run the X0 to the panel/disconnect and a bonding jumper back to the transformer case, and install the MBJ in the panel, also remember since you will have two different voltage systems in the building you will need to follow 210.5(C) as well as 200.6(D) which basically says you must have a different identification of the conductors for each voltage system including the neutral, many over look this requirement, if the 208 system uses a black, red blue with a white neutral then use a brown, orange, yellow with a gray neutral or in this case no neutral for the 480/277 system.

Also you will need to bond the secondary X0 back to the 208 system's neutral, this give the secondary a fault path if one of the secondaries ungrounded conductors was to fault to a grounding path for the 208 system, just do not bond the X0 on the primary side of this transformer if there is one, I know you said its a delta 208 volt primary but I have seen a few use a WYE/WYE transformer like this and just hook up the primary as a delta.

 

[LOCILOP]

No Neutral

No Neutral

Thank You. I will look this up in the code and see if NYC has any amendments to this.

There is no Neutral in the entire system. The prints & schedule only call for 3 conductors and the ground(Green) wire. So I am assuming that I will bond the ground(Green) wires to the chassis of the transformer.

There is a HO in the Transformer, but we didn't pull any neutrals what so ever.

 

[GoldDigger]

Also you will need to bond the secondary X0 back to the 208 system's neutral, this give the secondary a fault path if one of the secondaries ungrounded conductors was to fault to a grounding path for the 208 system, just do not bond the X0 on the primary side of this transformer if there is one, I know you said its a delta 208 volt primary but I have seen a few use a WYE/WYE transformer like this and just hook up the primary as a delta.

Since this is a step-up transformer, the secondary neutral point will be labelled H0, not X0, right? The OP also referred to the H0 terminal on the secondary side.

 

[hurk27]

Since this is a step-up transformer, the secondary neutral point will be labelled H0, not X0, right? The OP also referred to the H0 terminal on the secondary side.

Nice catch yep meant H0:ashamed1:

 

[hurk27]

There is no Neutral in the entire system. The prints & schedule only call for 3 conductors and the ground(Green) wire. So I am assuming that I will bond the ground(Green) wires to the chassis of the transformer.

There is a HO in the Transformer, but we didn't pull any neutrals what so ever.

If you don't bond the H0 you will have an ungrounded secondary and it will take two faults to open OCPD' this is why the NEC will require you to install a ground detection alarm system in 250.21(B) as mentioned in post 2 by Augie47 which will add cost to the installation, so if you can use a grounded system it might be a better choice as far as money goes.

 

[templdl]

If you don't bond the H0 you will have an ungrounded secondary and it will take two faults to open OCPD' this is why the NEC will require you to install a ground detection alarm system in 250.21(B) as mentioned in post 2 by Augie47 which will add cost to the installation, so if you can use a grounded system it might be a better choice as far as money goes.

Yes, if the is no reason to have an ungrounded system always opt to ground it even though a neutral isn't required. The simple idea that line to ground voltages are much lower than for an ungrounded system as well as should there be a L-G fault occur it will not clear an OCPD until a second line faults. Should the fault be arcing the voltage often exceeds What the L-L voltage is because of the system capacitance as I recall. I know that in an ungrounded delta that's a huge issue.
As Jim Dungar says "Just because you can, doesn't mean you should."

 

[hurk27]

Yes, if the is no reason to have an ungrounded system always opt to ground it even though a neutral isn't required. The simple idea that line to ground voltages are much lower that for an ungrounded system as well as should there be a L-G fault occur it will not clear an OCPD until a second line faults. Should the fault be arcing the voltage often exceeds What the L-L voltage is because of the system capacitance as I recall. I know that in an ungrounded delta that's a huge issue.
As Jim Dungar says "Just because you can, doesn't mean you should."

Personally I have never had a problem with an industrial ungrounded system as long as a ground fault alarm is used, there are many who have fears with them and think they are so dangerous, but if you think about it, since you don't have a first fault, arc flash is eliminated for the first fault to ground, as well as unexpected down time, and as long as you have a good ground fault alarm installed it gives you time to do an orderly shut down, to find the fault to make the repair, but you are correct that after a first fault you will have a higher voltage to ground, or even without a ground fault because of system capacitance coupling or inductance

Besides it can add cost to the installation for the ground alarm/monitor, and some equipment can not be on an ungrounded system many VFD's drives are not setup to run on an ungrounded system

One problem I have found (this doesn't apply to the OP) is there are a few who don't understand that you can not ground the X0 at service transformer and use the system as an ungrounded system even if the utility has only brought 3 conductors from the transformer to the service because once the secondary has been referenced to Earth even remotely you must provide a low impedance path all the way from the transformer to the service disconnect, as we have seen post on here and I have experienced also, some line men don't understand this and have replaced their delta transformer with a WYE and bonded the X0 at the pole or pad mount but still only had three wires to the service disconnect one case the lineman up sized a delta tree that was ungrounded then corner grounded it but did not re-bond the C phase at the meter leaving a 480 volts to earth reference that could have cause someone to get killed, luckily we got called when some 277 volt line to ground filters and MOV's let it's magic smoke out.

On a WYE without the low impedance fault path if a fault did happen all the grounding as well as anything connected to it would be at a 277 volt potential to remote Earth posing a very dangerous shock hazard to anyone making contact between Earth and the grounding system or anything connected to it, this would not be the case in the OP's SDS since his transformers X0 would not be referenced to earth if he did not ground it so he has the option of which way to go.

 

[templdl]

Personally I have never had a problem with an industrial ungrounded system as long as a ground fault alarm is used, there are many who have fears with them and think they are so dangerous, but if you think about it, since you don't have a first fault, arc flash is eliminated for the first fault to ground, as well as unexpected down time, and as long as you have a good ground fault alarm installed it gives you time to do an orderly shut down, to find the fault to make the repair, but you are correct that after a first fault you will have a higher voltage to ground, or even without a ground fault because of system capcitance coupling or inductance

Besides it can add cost to the installation for the ground alarm/monitor, and some equipment can not be on an ungrounded system many VFD's drives are not setup to run on an ungrounded system

One problem I have found (this doesn't apply to the OP) is there are a few who don't understand that you can not ground the X0 at service transformer and use the system as an ungrounded system even if the utility has only brought 3 conductors from the transformer to the service because once the secondary has been referenced to Earth even remotely you must provide a low impedance path all the way from the transformer to the service disconnect, as we have seen post on here and I have experienced also, some line men don't understand this and have replaced their delta transformer with a WYE and bonded the X0 at the pole or pad mount but still only had three wires to the service disconnect one case the lineman up sized a delta tree that was ungrounded then corner grounded it but did not re-bond the C phase at the meter leaving a 480 volts to earth reference that could have cause someone to get killed, luckily we got called when some 277 volt line to ground filters and MOV's let it's magic smoke out.

On a WYE without the low impedance fault path if a fault did happen all the grounding as well as anything connected to it would be at a 277 volt potential to remote Earth posing a very dangerous shock hazard to anyone making contact between Earth and the grounding system or anything connected to it, this would not be the case in the OP's SDS since his transformers X0 would not be referenced to earth if he did not ground it so he has the option of which way to go.

I can see by my post that Emailing late at night at is not a good thing.
Basically unless there is a good reason for an ungrounded system I always recommend that it be grounded. An ungrounded in my opinion should be an exception knowing that there are some good reasons for an ungrounded system and what it implies.
But you brought up some very interesting example as well as made some very good points.

 

[GoldDigger]

I can see by my post that Emailing late at night at is not a good thing.

If you must email under those conditions, at least turn off ought-to-correct to give us a better chance to decipher what you meant to say.

 

[hurk27]

I can see by my post that Emailing late at night at is not a good thing.
Basically unless there is a good reason for an ungrounded system I always recommend that it be grounded. An ungrounded in my opinion should be an exception knowing that there are some good reasons for an ungrounded system and what it implies.
But you brought up some very interesting example as well as made some very good points.

Yep when I don't cut my fingernails it seems I start clipping the keys just above the one I intend to hit, but I see you have the problem of hitting the key to the left of the intended target, no problem as I clearly understood what you wrote

If you must email under those conditions, at least turn off ought-to-correct to give us a better chance to decipher what you meant to say.

if you notice the "G" is just to the right of the "F" on a QWERTY keyboard so its very easy to hit the next key over and "ungrounded" turns into "unfounded", my problem is always catching the key above my target with my long fingernail, but my spell check catches it every time or at least points it out that the attempt at typing didn't cut the mustard :lol:

Because I use Internet Explorer I use IE Spell<<"Link alert"
which is a very good spell checker and doesn't use much system resources and it's easy to add to it's data base on the fly as not all words are in it, but from what I've heard it doesn't support Fire Fox or GG Chrome neither of which I use, it also allows you to just check what you highlighted, the only problem I found is it doesn't like some compound words and wants to separate them to which you just click ignore like subpanel it suggest sub panel or sub-panel, but you can click the add button to just add these compound words and it will quit asking on them.

The best part of it is it's free for home use:happyyes:

Another thing is the keyboard you use can make a world of difference, I liked the Microsoft Internet keyboards and ball-less mouse set and the next time I get out to Sam's Club I'll pick up a set as the keys are much larger then what I have on this stock OEM Dell keyboard and ball-less mouse set, the keys are much closer together and smaller on this dell keyboard and not much better then ones on their laptops. The keyboard I'm talking about isn't the split Ergonomic one that Microsoft also offers as I could not get use to one of those :happysad: also I don't like the Dell 7 button I.R mouse, as the two buttons on the side are too easy to hit which by default they are the browser forward and back buttons and if you hit them while making a post or filling out a form you wind up starting over because you moved from the web page and when you go back everything you typed is gone, so I programed them off, the two extra buttons on the scroll wheel are nice as while the wheel scrolls up and down these two buttons can be used to scroll left and right or when you don't have a left and right scroll bar it will move the cursor left and right through the post your typing which is great for editing.

 

[electrofelon]

Also you will need to bond the secondary X0 back to the 208 system's neutral, this give the secondary a fault path if one of the secondaries ungrounded conductors was to fault to a grounding path for the 208 system, just do not bond the X0 on the primary side of this transformer if there is one, I know you said its a delta 208 volt primary but I have seen a few use a WYE/WYE transformer like this and just hook up the primary as a delta.

I dont quite follow you here. Can you give a code reference for this? I mean I agree in theory but 1) I cant think of a scenario where a secondary would fault to the primary system but not the secondary system, unless there was a blateny code violation or wiring error like for example a secondary ungrounded conductor in a nonmetallic wiring method passed thru a metal box that was not bonded to the secondary system but was bonded to the primary system. 2) even if this were to happen, as long as an equipment grounding/bonding conductor was run with the primary supply to the transformer, this fault would have a path back to the secondary winding. Did you essentially mean to say. "run an equipment ground with the primary conductors and bond it to the transformer case"? AS long as these are grounded systems and the system is grounded properly and the equipment is grounded/bonded normally this is taken care of - Just sounds like you were implying something extra....