egc throughEMY

[robertcarbone]

Ran in to an existing situation I am replacing existing 75kva transformer 120/208y primary to 480volt delta secondary, feeder is run in EMT with no wire EGC they are using the EMt as the EGC which I believe you can do, it goes to a 3 phase disconnect, on the load side of disconnect going into transformer they have a 2 ft run of sealtite there is a ground wire in the sealtite going in to transformer correct out of transformer sealtite goes 4 ft to 480 volt disconnect with ground and goes to machine. My question is is the EMT still considered as a EGC on both the line & load side of transformer and do I have to go from the frame of transformer to building steel ?

 

[petersonra]

Ran in to an existing situation I am replacing existing 75kva transformer 120/208y primary to 480volt delta secondary, feeder is run in EMT with no wire EGC they are using the EMt as the EGC which I believe you can do,

I concur.

it goes to a 3 phase disconnect, on the load side of disconnect going into transformer they have a 2 ft run of sealtite there is a ground wire in the sealtite going in to transformer correct out of transformer sealtite goes 4 ft to 480 volt disconnect with ground and goes to machine. My question is is the EMT still considered as a EGC on both the line & load side of transformer

the EGC is not really associated with the transformer so much as it is associated with the circuit conductors, so the EMT can only be the EGC for the circuit conductors supplying the xfmr.

and do I have to go from the frame of transformer to building steel ?

Your description suggests you have created an SDS and that will require a connection to the closest qualifying grounding electrode. That may or may not be building steel.

 

[ActionDave]

Your description suggests you have created an SDS and that will require a connection to the closest qualifying grounding electrode. That may or may not be building steel.

And the GEC can be in the transformer or the first disconnect, wherever the XO is bonded.

 

[electricalist]

Was the a gec connected to the existing xfmr? Grounding Electrode Conductor.

 

[robertcarbone]

EGC through EMT

EGC through EMT

sincexfmr is considered a sds I have building steel available so that would be my preference for grounding would you agree?

 

[electricalist]

My preference would be the gec that was connected to the existing xfmr and because the bldg has steel doesn't mean it qualifies as a gec. Is the bldg steel part of an existing GES ?

 

[ActionDave]

sincexfmr is considered a sds I have building steel available so that would be my preference for grounding would you agree?

Here is what the code says

250.30 (4) Grounding Electrode. The grounding electrode shall
be as near as practicable to, and preferably in the same area
as, the grounding electrode conductor connection to the sys-
tem. The grounding electrode shall be the nearest of one of
the following:
(1) Metal water pipe grounding electrode as specified in
250.52(A)(1)
(2) Structural metal grounding electrode as specified in
250.52(A)(2)

Exception No. 1: Any of the other electrodes identified in
250.52(A) shall be used if the electrodes specified by
250.30(A)(4) are not available.

Exception No. 2 to (1) and (2): If a separately derived sys-
tem originates in listed equipment suitable for use as ser-
vice equipment, the grounding electrode used for the service
or feeder equipment shall be permitted as the grounding
electrode for the separately derived system.

 

[petersonra]

And the GEC can be in the transformer or the first disconnect, wherever the XO is bonded.

what X0? The OP indicated a delta secondary.

 

[electricalist]

Then it's H-O and the GEC?

 

[kwired]

Here is what the code says

I think the code needed quoted - seems when this kind of question comes up many replies simply state that it is necessary to bond to building steel, though that may be fairly common method that gets applied, that is not what requirements state, and in fact if there is no building steel or other GES components are closer things can change.

what X0? The OP indicated a delta secondary.

Then it's H-O and the GEC?

Grounded conductor of the secondary - can't go wrong with that, and if there is no grounded conductor you still need the transformer frame connected to the GES.

 

[petersonra]

Then it's H-O and the GEC?

I don't think there is any circumstance where you would bond the GEC to H0 and still be code compliant.

An ungrounded delta system just does not have any of the circuit conductors grounded. In such a case, the GEC would be bonded to the EGC at the xfmr, likely to the stud on the case that is conveniently supplied.

 

[ActionDave]

what X0? The OP indicated a delta secondary.

Oops. Missed that.

 

[electricalist]

Point taken. Then as stated the frame

 

[kwired]

I don't think there is any circumstance where you would bond the GEC to H0 and still be code compliant.

An ungrounded delta system just does not have any of the circuit conductors grounded. In such a case, the GEC would be bonded to the EGC at the xfmr, likely to the stud on the case that is conveniently supplied.

Where permitted a backfed transformer where you are separatey deriving the higher voltage that would happen to have a HO terminal would be a case where you would/could connect the GEC there. Sort of rare to be in such a situation but not impossible - usually the high voltage side is delta configured.

Just because there are only three output conductors doesn't mean it will be ungrounded, it can be corner grounded on any output lead - there won't be an H0 on such systems though.