480V to 240/120V three phase transformer

[hhsting]

I have spa and tanning beds. The engineer is specifying 480V to 240/120V three phase transformer. The engineer has the following note in the plans:

I am not sure how to ground this transformer such as will this have system bonding jumper or not? If it does then is their a neutral if not then what gets "neutral to equipment ground" bond? Is it a separately derived system or not? Also, where would the secondary side neutral be tied to?

Can anyone here please help me understand all the questions above.

 

[infinity]

Since the secondary is a 4 wire Delta there will be a center tap for the neutral on one winding. That gets the SBJ just like a Wye secondary.

 

[jap]

There will be a neutral but it's generally a reduced capacity lighting tap rated at roughly 5% of the rated kva.

JAP>

 

[hillbilly1]

It will be delta connected. Be careful with any 120 volt loads that also have the high leg present. I connected a German made tanning bed many years ago that required 240 volt three phase. The engineer said it did not need a neutral, which was great, except it did. The German manufacturer used the equipment ground as a neutral for the 120 volt controls. Luckily I caught it before we energized it.