Neutral Backfeed

[Smart $]

you would be correct. the transformer is properley grounded to the main grounding conductor as well as building steel. the neutral is created in the transformer as its delta/wye. you wouldnt bond them there would you?

Grounded, GEC EGC, SBJ are (should be) all bonded at one location, in one enclosure. From what your earlier posts states, it is properly "bonded". Bonded is in quotation marks because loose connections rescind the "properly"

... the main disconnect for the entire building itself has the neutral and ground bonded. my subpanel does not have them bonded...

Can you recreate the scenario now, since you have energized everything? Did you check for voltage on the circuits when this happened, or did you just assume there was no voltage because the breakers were in the off/tripped position? I'm asking because on very [very, very] rare occasions a breaker (even a new one) will "temporarily" be defective.

 

[K2500]

you would be correct. the transformer is properly grounded to the main grounding conductor as well as building steel. the neutral is created in the transformer as its delta/Wye. you wouldn't bond them there would you?

Would I bond the neutral(X0) of my transformer to the grounding electrode conductor(s), the building steel, and the equipment grounding conductor, in the transformer? You bet I would.

 

[cadpoint]

One of your secondary panel neutral's is touching or grouped with one of the main panel neutral's both just branch circuits. MBG

 

[notoriousdln]

into the xformer i have a-b-c with a ground and no neutral. from the xformer i have a-b-c-n with a ground. x0 is not bonded to the ground, but the subpanel is grounded with its own grounding conductor. from what i know x0 is not required to be bonded? do any of you believe that could be the cause...because the secondary neutral is not bonded? what gets me is that other circuits from the SAME secondary panel do not have this problem. just these 8 circuits feeding this little upfit. my thinking was that its something to do with the circuits being multi-wire circuits, but ive never had that problem before, and like i said those breakers were off, and the ungroundeds did not have voltage.

 

[K2500]

into the xformer i have a-b-c with a ground and no neutral. from the xformer i have a-b-c-n with a ground. x0 is not bonded to the ground, but the sub-panel is grounded with its own grounding conductor. do any of you believe that could be the cause...because the secondary neutral is not bonded?

I believe the previous 20 posts said exactly that.

from what i know x0 is not required to be bonded?

It is.

what gets me is that other circuits from the SAME secondary panel do not have this problem. just these 8 circuits feeding this little up-fit. my thinking was that its something to do with the circuits being multi-wire circuits, but ive never had that problem before, and like i said those breakers were off, and the ungroundeds did not have voltage.

Stranger things have happened.

 

[erickench]

If neither transformer neutral or the subpanel neutral is bonded to the EGC then it is an ungrounded system. If you bonded either neutral to the EGC you would get a zero voltage reading.

 

[kwired]

you would be correct. the transformer is properley grounded to the main grounding conductor as well as building steel. the neutral is created in the transformer as its delta/wye. you wouldnt bond them there would you?

The transformer creates what is called a separately derived system.

The secondary windings have no electrical connection to the primary windings making them a totally separate system which is why the term separately derived is used. Any other source that has no direct electrical connection to the service is also called a separately derived system.

You have to establish a grounding point on this system. It could be any point on the system but the NEC will require it to be the common point on a wye system or the center tap on a single phase three wire system. If it were a two wire transformer you can ground either line, if it is a corner grounded delta you can ground any phase you want.

The POCO does the same thing on your service. Their transformer is a separately derived system from their distribution voltage. They have to bond the XO point or other point intended to be grounded to a grounding electrode and usually to the primary neutral also which is connected to multiple electrodes. This will help ensure that anything that is at earth potential will remain at the same potential in relation to other system conductors.

 

[notoriousdln]

understood. thanks guys.

 

[Smart $]

understood. thanks guys.

I thought you said neutral was bonded to ground at the main disconect in Post #16???

The neutral (aka X0) does not (under ordinary, intentional circumstances) get bonded to the grounding system at more than one location. If bonding occurs at the main disconnect then there is no bonding of X0 in the transformer enclosure.

 

[notoriousdln]

thats what i thought, but from what others on here are saying once its through the transformer its seperatley derived, so they need to be bonded again, from what i understand that they are saying.

 

[Smart $]

thats what i thought, but from what others on here are saying once its through the transformer its seperatley derived, so they need to be bonded again, from what i understand that they are saying.

Oh... perhaps I misunderstood. I was thinking the transformer was before what you referred to as the main disconnect, since you called your 8-circuit panel a subpanel. Please confirm order of all equipment involved from service disconnect to your panel...

 

[notoriousdln]

the MAIN Panel contains the main disonnect and also the breaker that feeds my panels transformer. the transformer feeds my panel which contains the 8 circuits that feed the fit up.

 

[Smart $]

the MAIN Panel contains the main disonnect and also the breaker that feeds my panels transformer. the transformer feeds my panel which contains the 8 circuits that feed the fit up.

As such, the transformer's secondary is a separately derived system. The neutral conductor is required to be bonded as mentioned previously.

 

[benaround]

dln,

In the transformer you need at least one double lug on the XO terminal. One neutral needs

to go to the panel, the other needs to go to the EG bar in the transformer. The EG bar

needs all the EGC's and GEC(s) and the afore mentioned neutral all landed on it.

Q. You keep refering to your sub-panel, I am hoping that this panel has a 'Main Breaker'

installed in it ?

side note: Getting shocked is no fun, but, you should be thankful that it was you, because

it is now going to get fixed and not be left to hurt/kill an innocent tenant. You are very

lucky. I hope this effects the way you handle jobs in the future, knowledge is the key.

 

[Smart $]

dln,

In the transformer you need at least one double lug on the XO terminal. One neutral needs

to go to the panel, the other needs to go to the EG bar in the transformer. The EG bar

needs all the EGC's and GEC(s) and the afore mentioned neutral all landed on it.

...

This is if bonding is done at the transformer. It may be bonded at the system disconnecting means, or anywhere in between though usually not practical.

..and the neutral is not landed on the EG bar (and X0... just X0). The GEC can land on either X0 or EG bar. The conductor from X0 to EG bar is the System Bonding Jumper (SBJ).

 

[benaround]

This is if bonding is done at the transformer. It may be bonded at the system disconnecting means, or anywhere in between though usually not practical.

..and the neutral is not landed on the EG bar (and X0... just X0). The GEC can land on either X0 or EG bar. The conductor from X0 to EG bar is the System Bonding Jumper (SBJ).

Thanks for that useful information, I'm pretty sure the OP will understand, I thought a guy

like you would of understood also, just goes to show you never know.

 

[Smart $]

Thanks for that useful information, I'm pretty sure the OP will understand, I thought a guy

like you would of understood also, just goes to show you never know.

Oh I understood... except for the part about landing the neutral on the EG bar

 

[benaround]

Have you ever looked into golf or oil painting, maybe coin collecting ?

 

[Smart $]

Have you ever looked into golf or oil painting, maybe coin collecting ?

Considered all of those at one time or another. To date, they all remain as considered.

 

[notoriousdln]

the subpanel is a main breaker panel, i suppose i could install the bonding jumper in that panel and all will be solved then?