I am doing my first I.G system. From what I have read is, you bond all of your grounding conductors together at the transformer. The system is a 480 panel feeding a 120\208 trans. So I should bond them together and seperate the ground and the neutral at the 120 panel. Any help Thanks

Sparks30;

Sounds like you have a Step-Down Transformer within the premisis, which will be driving the 208Y/120 VAC Equipment (a Separately Derived System, in other words), you will connect all the Grounding and Grounded Conductors + the Grounding Electrode Conductor and Main Bonding Jumper to the XO Terminal of the Secondary.
At the first Panelboard (actual name for "Sub Panel"), the Grounded Conductor - AKA "Neutral" will terminate on a Bus, which is Isolated / Insulated from the Panelboard's Enclosure (the "Can").

The EGC (Equipment Grounding Conductor) lands on either a Lug, or a Grounding Bus which is Electrically connected to the metallic enclosure - thereby Bonding the Enclosure.

For the IGC (Isolated Grounding Conductor), setup an additional Isolated / Insulated Bus kit - similar to the one for the System's Grounded Conductor (no Electrical connection at the Panelboard), and land the IGCs for both the Branch Circuits and the IGC "Feeder" from the Transformer, on this Bus.

Since there will be quite a few terminations to the "XO" point, get a multi Conductor lug (3 or 4 Conductor) to mount on "XO", land the Grounded Conductor(s), the Grounding Electrode Conductor and the Main Bonding Jumper to "XO".
Use an additional multi Conductor lug on the Transformer's Enclosure, then land the Main Bonding Jumper, the EGCs and the IGCs to this lug.

Below is a drawing that may help - just "convert" the system to an SDS, instead of a PoCo supplied system.
This Drawing is IG Details #1 , which is located in the Technical Reference Section .
Many more items may be found in the same area.

Scott35

This is great info but the drawings do not match my setup. I have a utility co transformer that feeds a 277/480 switchgear. From there it goes to a 277/480 panel. The 277/40 panel feeds the 277/480 step down transformer 120/208. In this x-former should I bond all grounded and grounding conductors together. Thanks

Sparks30;


Yes!


Scott35