Transformer bonding/grounding

[meatzaman]

I have a 15 KW single Phase 480 - 240 transformer, the ground coming in with the conductors, does it just ground the chassis or does it also go to the center tap, do I have to go to the ground rods from the transformer, and if I just ground the chassis do I just take a nuetral to the 120/240 panel and bond the neutral bar and make ground rod connection there

 

[raider1]

Welcome to the forum.

I have a 15 KW single Phase 480 - 240 transformer, the ground coming in with the conductors, does it just ground the chassis or does it also go to the center tap,

The equipment grounding conductor that is brought with the primary conductors is connected to the frome of the transformer.

A system bonding jumper is required to be installed on the secondary of the transformer in accordance wiht 250.30(A)(1)

do I have to go to the ground rods from the transformer

You are required to connect the separatly derived system to the building grounding electrode system in accordance with 250.30(A)(3) for a single separatly derived system. You can't just use isolated ground rods.

and if I just ground the chassis do I just take a nuetral to the 120/240 panel and bond the neutral bar and make ground rod connection there

You can install the system bonding jumpoer and the connection the the gounding electrode system at either the transformer or the first disconnecting means but make sure that you don't install them at both locations.

I would recommend checking out 250.30 for the grounding and bonding requirements for a transformer.

Chris

 

[tryinghard]

I have a 15 KW single Phase 480 - 240 transformer, the ground coming in with the conductors, does it just ground the chassis or does it also go to the center tap, do I have to go to the ground rods from the transformer, and if I just ground the chassis do I just take a nuetral to the 120/240 panel and bond the neutral bar and make ground rod connection there

Chris asweres great but here's perspective that may help as well

Terminate the EGC with the primary on the frame, its the effective fault path from its source upstream

The secondary receives induced voltage from the primary through air, no physical connection, because of this it?s considered separately derived so it needs its equipment grounding & earth connection (if its a grounded type system). The secondary also does not include a grounded conductor (neutral) until one of its windings are connected to a feeder neutral conductor and this connection needs to be bonded to establish effective fault path on equipment as well as reestablished earth connection the bonding needs to take place at same location as the grounding electrode connection ? either at the XFMR or at the first disconnect.