Y Delta woes - Electrician Talk - Professional Electrical Contractors Forum
CLICK HERE AND JOIN OUR COMMUNITY TODAY, IT'S FREE!
Go Back   Electrician Talk - Professional Electrical Contractors Forum > Electrical Trade Topics > NEC Code Forum


Like Tree39Likes
Reply
 
Thread Tools Display Modes
Old 01-19-2018, 09:17 PM   #1
Retired Account
 
Join Date: Mar 2011
Location: the Green Mountain state
Posts: 39,722
Rewards Points: 14,650
Default Y Delta woes

So i've a Y to delta 480.

But i'm not reading anything from phase to ground

this can't be right.....shouldn't it have been corner/center grounded?

~CS~
chicken steve is offline   Reply With Quote
Join Contractor Talk

Join the #1 Electrician Forum Today - It's Totally Free!

ElectricianTalk.com - Are you a Professional Electrical Contractor? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's the leading place for electricians to meet online. No homeowners asking DIY questions. Just fellow tradesmen who enjoy talking about their business, their trade, and anything else that comes up. No matter what your specialty is you'll find that ElectricianTalk.com is a great community to join. Best of all it's totally free!

Join ElectricianTalk.com - Click Here JOIN FOR FREE


Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ElectricianTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

Sponsored Links
Advertisement
 
Old 01-19-2018, 09:41 PM   #2
Registered Member
 
Join Date: Feb 2008
Location: Alabama
Posts: 11,885
Rewards Points: 1,360
Default

Need more info.
nolabama likes this.
RePhase277 is offline   Reply With Quote
Old 01-19-2018, 09:45 PM   #3
Modérateur
 
frenchelectrican's Avatar
 
Join Date: Mar 2007
Location: Philippines
Posts: 8,635
Rewards Points: 21,782
Default

Quote:
Originally Posted by chicken steve View Post
So i've a Y to delta 480.

But i'm not reading anything from phase to ground

this can't be right.....shouldn't it have been corner/center grounded?

~CS~
where did ya read the voltage ?

did ya read from line to line and line to ground and what the numbers ya hitting ?
__________________
Bleu est beau.
frenchelectrican is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 01-20-2018, 05:49 AM   #4
Retired Account
 
Join Date: Mar 2011
Location: the Green Mountain state
Posts: 39,722
Rewards Points: 14,650
Default

line/line is all 480

line to G is 0 , or a few residual volts French One

I'm thinking the secondary isn't make to XO

Thus it can't carry a fault.....am i wrong?

~CS~
chicken steve is offline   Reply With Quote
Old 01-20-2018, 07:15 AM   #5
Retired Account
 
Join Date: Mar 2011
Location: the Green Mountain state
Posts: 39,722
Rewards Points: 14,650
Default

I have an 'ungrounded delta' , (via others) that i'm making straight (no noodle) 480V branch circuits off of

>>>




Can anyone validate the grounding in art 250?

~CS~
nolabama likes this.
chicken steve is offline   Reply With Quote
Old 01-20-2018, 08:00 AM   #6
Modérateur
 
frenchelectrican's Avatar
 
Join Date: Mar 2007
Location: Philippines
Posts: 8,635
Rewards Points: 21,782
Default

Quote:
Originally Posted by chicken steve View Post
line/line is all 480

line to G is 0 , or a few residual volts French One

I'm thinking the secondary isn't make to XO

Thus it can't carry a fault.....am i wrong?

~CS~
Quote:
Originally Posted by chicken steve View Post
I have an 'ungrounded delta' , (via others) that i'm making straight (no noodle) 480V branch circuits off of

>>>




Can anyone validate the grounding in art 250?

~CS~
Chicken Steve .,

Just be extra carefull with ungrounded delta system they will bite ya pretty hard if you are not aware of this .

Did the service is actually ungrounded delta ? if so they should have a ground fault indenticator lights or others means for ground fault.

Look up in art 250 but there few spots you will have to find it due it will be in at least 3 or 4 spots for sure plus I think it mention in art 310 but not sure due I havent look at nec code book recentally. so expect in few places.

Yes the ungrounded delta can carry single phase fault with out affect the system typically line to ground but line to line fault yes it will either blow the fuse or trip the breaker.

Myself and few other guys in here have allready dealt with ungrounded system it is a pain in arse if not aware at the source.

but if you need single phase load., you will need SDS single phase transfomer and follow the SDS rules on that.

What this unground load is going to be feed for ? motor load or transfomer ?

If you do see the transfomer then did you see how the secondary been hooked ? If so what type of transfomer it was ? typically I useally ran into are isolation or drive transfomer typically 1:1 ratio
__________________
Bleu est beau.
frenchelectrican is offline   Reply With Quote
Old 01-20-2018, 08:11 AM   #7
Retired Account
 
Join Date: Mar 2011
Location: the Green Mountain state
Posts: 39,722
Rewards Points: 14,650
Default CS

[quote=frenchelectrican;4703242]Chicken Steve .,

Quote:
Just be extra carefull with ungrounded delta system they will bite ya pretty hard if you are not aware of this .
yeah i get that FrenchOne

Quote:
Did the service is actually ungrounded delta ? if so they should have a ground fault indenticator lights or others means for ground fault.
No, the incoming service is 208/120 3 phase Y , this Xformer sits right next to that main 800A disco, Y to D, then goes into a trough with both voltage disco's mounted above it, (480 & 208/120)


Quote:
Look up in art 250 but there few spots you will have to find it due it will be in at least 3 or 4 spots for sure plus I think it mention in art 310 but not sure due I havent look at nec code book recentally. so expect in few places.
Yeah, been looking , but just can't quite put my finger on the 'letter of code' here.....

Quote:
Yes the ungrounded delta can carry single phase fault with out affect the system typically line to ground but line to line fault yes it will either blow the fuse or trip the breaker.
I'm unsure how, i get no readings H to G , so i'm lost as to how the fault path occurs back to XO , especially if there is no connection to it

Quote:
Myself and few other guys in here have allready dealt with ungrounded system it is a pain in arse if not aware at the source.

but if you need single phase load., you will need SDS single phase transfomer and follow the SDS rules on that.

What this unground load is going to be feed for ? motor load or transfomer ?
It's in a 250Ksq ft facility with a bunch of starving artists who are all glass blowers, and want me to hook up their furnaces (all straight 480 3 ph)

Quote:
If you do see the transfomer then did you see how the secondary been hooked ? If so what type of transfomer it was ? typically I useally ran into are isolation or drive transfomer typically 1:1 ratio
All i know is it's Y primary D secondary

I haven't taken the cover off to investigate, nor can (or will) i unless i can shut the building down

Now i'm wondering about it's (the Xfomrer's) prim & sec protection as well via 450

I hate walking into someone else's 'effin' mess.....~CS~
chicken steve is offline   Reply With Quote
Old 01-20-2018, 08:25 AM   #8
Hackenschmidt
 
splatz's Avatar
 
Join Date: May 2015
Location: Parts Unknown
Posts: 8,846
Rewards Points: 326
Default

The ungrounded system has no grounded conductor. Since none of the conductors are grounded, there's no potential between ground and any of the L1 L2 L3 terminals.

At the first ground fault, you basically have a corner grounded delta rather than an ungrounded delta. You need the ground fault detection to tell you something's wrong.

When the second ground fault occurs, is when it gets ugly.

https://iaeimagazine.org/magazine/20...ly-ungrounded/
__________________
Everything Should Be Made as Simple as Possible, But Not Simpler
splatz is online now   Reply With Quote
The Following User Says Thank You to splatz For This Useful Post:
chicken steve (01-20-2018)
Old 01-20-2018, 08:37 AM   #9
Modérateur
 
frenchelectrican's Avatar
 
Join Date: Mar 2007
Location: Philippines
Posts: 8,635
Rewards Points: 21,782
Default

[quote=chicken steve;4703266]
Quote:
Originally Posted by frenchelectrican View Post
Chicken Steve .,



yeah i get that FrenchOne

FE: Good then you are aware of it.


No, the incoming service is 208/120 3 phase Y , this Xformer sits right next to that main 800A disco, Y to D, then goes into a trough with both voltage disco's mounted above it, (480 & 208/120)


FE: Look below for more comment I will get both details in one shot.

Yeah, been looking , but just can't quite put my finger on the 'letter of code' here.....

FE:I dont have the NEC code book with me right now cuz I am sitting on ferry boat now due generator issue. but yes I do recall the NEC did cover at least 4 parts as soon I get the numbers I will posted for ya.



I'm unsure how, i get no readings H to G , so i'm lost as to how the fault path occurs back to XO , especially if there is no connection to it

FE:The XO is never used in reverse connection in transfomer at all. either they leave it floating or corner ground it that is the only two way you can advoid the issue with delta secondary.

But if you have grounding conductor in there it will never be tied to XO and it will be a straight shot thru the transfomer housing.

second thing I been wondering about the transfomer size due you mention electric furances what the glass blowers want. that will bite ya so check it ahead of it.




It's in a 250Ksq ft facility with a bunch of starving artists who are all glass blowers, and want me to hook up their furnaces (all straight 480 3 ph)



All i know is it's Y primary D secondary

I haven't taken the cover off to investigate, nor can (or will) i unless i can shut the building down

Now i'm wondering about it's (the Xfomrer's) prim & sec protection as well via 450

I hate walking into someone else's 'effin' mess.....~CS~

If you did check the transfomer size I can tell you what is the correct OCPD it supposed to be.,

For conventail 75 KVA units the 480 volts side typically be in 90 amp range while 208 side will be 200 amp unless upsized for primary duty which the inrush current may trip the breaker especially if you have 208 primary side.

That based with proper conductor size in there but if differnt size conductor that can change game on that.

Oh I been into other mess pretty often and some case I just dont like it but have to do it ( only if they sign the paper and get it to meet the code.)
__________________
Bleu est beau.

Last edited by frenchelectrican; 01-20-2018 at 08:40 AM.
frenchelectrican is offline   Reply With Quote
Old 01-20-2018, 08:54 AM   #10
Retired Account
 
Join Date: Mar 2011
Location: the Green Mountain state
Posts: 39,722
Rewards Points: 14,650
Default

Spot on Mr Splatz.....


and yes it's this....



with ref to >>>
250.4 General Requirements for Grounding and Bonding.
(B) Ungrounded Systems.
4>>>


Quote:
(4) Path for Fault Current. Electrical equipment, wiring, and
other electrically conductive material likely to become ener‐
gized shall be installed in a manner that creates a low-
impedance circuit from any point on the wiring system to the
electrical supply source to facilitate the operation of overcur‐
rent devices should a second ground fault from a different
phase occur on the wiring system
. The earth shall not be
considered as an effective fault-current path.
BUT, there is no >>>
250,21(B) Ground Detectors. Ground detectors shall be installed

Mr Lofland's sign off got me>>>

Quote:
What are you waiting for?

Regardless of whether a grounded or ungrounded system is employed, both systems will be grounded. Don’t let the term “ungrounded” fool you. As we have discussed in this article, there is nothing “ungrounded” about an ungrounded system. Relax and have another piece of cake.
I think i've got a ligit complaint here.....

~CS~
chicken steve is offline   Reply With Quote
Old 01-20-2018, 08:58 AM   #11
Retired Account
 
Join Date: Mar 2011
Location: the Green Mountain state
Posts: 39,722
Rewards Points: 14,650
Default

[quote=frenchelectrican;4703298]
Quote:
Originally Posted by chicken steve View Post


If you did check the transfomer size I can tell you what is the correct OCPD it supposed to be.,

For conventail 75 KVA units the 480 volts side typically be in 90 amp range while 208 side will be 200 amp unless upsized for primary duty which the inrush current may trip the breaker especially if you have 208 primary side.

That based with proper conductor size in there but if differnt size conductor that can change game on that.

Oh I been into other mess pretty often and some case I just dont like it but have to do it ( only if they sign the paper and get it to meet the code.)
I'm going to pull off until next week, i'll go next week with some code enlightenment and firepower from you guys,(thank you all!) and come back with a few more specifics on this FrenchOne

I'll be involving my AHJ on this

Can't afford loosing any more tail feathers on this sort of thing.....~CS~
chicken steve is offline   Reply With Quote
Old 01-20-2018, 09:41 AM   #12
Registered Member
 
Join Date: Feb 2008
Location: Alabama
Posts: 11,885
Rewards Points: 1,360
Default

The person who put the transformer in originally didn't know what they were doing, most likely. If this were an industrial facility with a maintenance crew to watch the place, an ungrounded system might be OK. But with hippies and acid - dropping Vermont artists touching the equipment, it's probably best grounded.

Just ground one phase to the case and GEC. Use a Kenny clamp if think you are required to (you're not). Identify the grounded phase conductor white. You treat that phase just like it was a neutral, which means no fuses in that conductor.
RePhase277 is offline   Reply With Quote
Old 01-20-2018, 09:46 AM   #13
MTW
Senior Member
 
Join Date: Aug 2013
Location: Northeast USA
Posts: 15,196
Rewards Points: 9,560
Default

Call an electrician.
macmikeman, nolabama, ppsh and 1 others like this.
MTW is offline   Reply With Quote
The Following User Says Thank You to MTW For This Useful Post:
macmikeman (01-20-2018)
Old 01-20-2018, 09:50 AM   #14
Modérateur
 
frenchelectrican's Avatar
 
Join Date: Mar 2007
Location: Philippines
Posts: 8,635
Rewards Points: 21,782
Default

Quote:
Originally Posted by RePhase277 View Post
The person who put the transformer in originally didn't know what they were doing, most likely. If this were an industrial facility with a maintenance crew to watch the place, an ungrounded system might be OK. But with hippies and acid - dropping Vermont artists touching the equipment, it's probably best grounded.

Just ground one phase to the case and GEC. Use a Kenny clamp if think you are required to (you're not). Identify the grounded phase conductor white. You treat that phase just like it was a neutral, which means no fuses in that conductor.
Chicken steve .,

What both spatz and Rephase277 mention very clear and myself I feel what Rephase been talking about and it more common to corner grounded it and with true three phase loads like electric furance they dont affect the CG system at all. it been the same way with electric motors for years.

I have a feeling that someone miss the crictial step when they install the upstep transformer.
splatz likes this.
__________________
Bleu est beau.
frenchelectrican is offline   Reply With Quote
The Following User Says Thank You to frenchelectrican For This Useful Post:
splatz (01-20-2018)
Old 01-20-2018, 10:42 AM   #15
Retired Account
 
Join Date: Mar 2011
Location: the Green Mountain state
Posts: 39,722
Rewards Points: 14,650
Default

Quote:
Originally Posted by RePhase277 View Post
Just ground one phase to the case and GEC. Use a Kenny clamp if think you are required to (you're not). Identify the grounded phase conductor white. You treat that phase just like it was a neutral, which means no fuses in that conductor.
yup...

~CS~

Last edited by chicken steve; 01-20-2018 at 10:48 AM.
chicken steve is offline   Reply With Quote
Old 01-20-2018, 10:47 AM   #16
Retired Account
 
Join Date: Mar 2011
Location: the Green Mountain state
Posts: 39,722
Rewards Points: 14,650
Default

[quote=frenchelectrican;4703522]
Quote:
Chicken steve .,

What both spatz and Rephase277 mention very clear and myself I feel what Rephase been talking about and it more common to corner grounded it and with true three phase loads like electric furance they dont affect the CG system at all. it been the same way with electric motors for years.
I could ground a phase, or introduce a grounding detector system

grounding a ph means i have to run around revisiting different voltages some 480 equipment having control xfomers may not like

a detector system , at least to my understanding, makes it all complaint

Quote:
I have a feeling that someone miss the crictial step when they install the upstep transformer.
Yup

But the ET sparks caught it , and it'll have to come to light for me to continue to pump any 480 circuitry around, which i'm liable for proper grounding of

~CS~
chicken steve is offline   Reply With Quote
Old 01-20-2018, 02:01 PM   #17
Senior Member
 
Southeast Power's Avatar
 
Join Date: Jan 2009
Location: Florida
Posts: 17,927
Rewards Points: 8,532
Default

Your equipment will never know you grounded a corner so, you are good there.
Also, you mentioned OX. Just to recap for visitors that might not read the entire thread. Don't connect anything to OX when you are using a delta wye transformer backwards.
Southeast Power is online now   Reply With Quote
Old 01-20-2018, 02:14 PM   #18
Retired Account
 
Join Date: Mar 2011
Location: the Green Mountain state
Posts: 39,722
Rewards Points: 14,650
Default

Quote:
Originally Posted by Southeast Power View Post
Your equipment will never know you grounded a corner so, you are good there.
Also, you mentioned OX. Just to recap for visitors that might not read the entire thread. Don't connect anything to OX when you are using a delta wye transformer backwards.
Ok then i'm lost SP....~CS~
chicken steve is offline   Reply With Quote
Old 01-20-2018, 04:25 PM   #19
Registered Member
 
Join Date: Feb 2008
Location: Alabama
Posts: 11,885
Rewards Points: 1,360
Default

Quote:
Originally Posted by chicken steve View Post
yup...

~CS~
So you're saying you already knew? Why ask then?
RePhase277 is offline   Reply With Quote
Old 01-20-2018, 06:13 PM   #20
Retired Account
 
Join Date: Mar 2011
Location: the Green Mountain state
Posts: 39,722
Rewards Points: 14,650
Default

No i don't know the best way to deal with this, yes i am asking

Isn't that what this place is for 277?

~CS~
chicken steve is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Delta High leg breaker brother General Electrical Discussion 5 12-23-2017 03:07 PM
4 wire delta & open delta Madmax73 General Electrical Discussion 6 02-01-2017 11:26 AM
Open delta open wye transformer bank Lone Crapshooter Industrial Electrical Forum 15 09-15-2016 02:42 PM
Why is there a netural in Y and not Delta loads? ThatApprentice General Electrical Discussion 12 09-05-2016 07:15 PM
has anyone ever wire a delta to delta transformer? mike883 General Electrical Discussion 13 06-07-2016 08:38 AM


All times are GMT -4. The time now is 11:06 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com