FloatingWyeDelta
New User
- Location
- Indiana
- Occupation
- Worker
I am not an electrician, and this is the first time I've used a forum so I might not be using the correct NEC terminology and might not know the proper forum practices but I'm just trying to understand how this setup should look in the field. I'm not the one wiring it, I'm hoping to find a good article that shows what to do with the neutral, grounds, and bonds for this setup. I have a commercial service that has a 208Y/120v 3 phase 4-wire wye feed coming from the utility that is being used to reverse feed a delta-wye step down transformer made to step down 480v 3ph 3-wire delta to 208Y/120v 3ph 4-wire wye. So, in this application they are using the step-down transformer and reverse feeding it to step up the 208Y/120v 3ph 4-wire wye to a 480v delta and using it for a 480v welder. They are connecting the 208Y/120v 3ph 4-wire wye feed from the utility to the low side X# terminals and connecting the 3ph 480v main panel to the H# terminals. The service from the utility ABC&N goes inside to a main 3ph disconnect, then from the main 3ph disconnect it goes to a 3ph fused disconnect, then from the 3ph fused disconnect to the dry-type transformer X# terminals, then from the H# terminals it goes to a 3ph panel. Where should the neutral stop/terminate? Should it stop at the 3ph main disconnect, should it continue to the 3ph fused disconnect, should it continue to the dry-type transformer, should it continue all the way to the 3ph panel? Where should a ground be placed, where should bonding be placed. I've read some articles that explain that the neutral should not be connected in any way to the XO of the dry-type transformer, that the ground strap should be removed from the X0 to ground, and that the neutral should not even be ran to the ground lug on the dry-type transformer. But does the neutral need to still pass thru and go all the way to the 3ph main and just not connect to the transformers XO and the transformer ground lug. Or should it stop at the fused disconnect or the main disconnect? Also, what should the 3ph 480v breaker panel look like. Should it just have a ground going to it? Should the neutral be ran to it as well. If the neutral is supposed to go to the 3ph 480v breaker panel should the neutral and ground be bonded together? I have read that the 480v delta system can be either grounded (corner grounded delta) or ungrounded and different rules apply depending on what is chosen. If it's determined to be grounded what should the 480v panel look like as far as grounding (I've read that Bph should be grounded if this is chosen and labeled correctly and not have any overcurrent protection on that phase). If it's determined to be un-grounded what should the 480v panel look like as far as grounding (Just the enclosure grounded only). This one is complicated to figure out.
