Safe solution or not

[petersonra]

You might be better off putting the lower voltage transformer over by the new loads.

 

[__dan]

You might be better off putting the lower voltage transformer over by the new loads.

Not this one ..

View attachment 2562694



I'm trying to eliminate having a 60 A 120 v panel if possible.

The neutral for a 120/240V output would be provided at the X2,X3 connection. It would need to be bonded to the EGC and connected to a GES.

This exactly^^^.

480 V single phase to H1 - H4. H2 jumpered to H3 floats.

Secondary is separately derived, no primary side neutral. X2 jumpered to X3 + then connect system bonding jumper to the common neutral and grounding busbar, where the EGC, GEC, secondary system neutral all connect at a single point. X4, X1, neutral, is 120 / 240. If it provides a winding tap for the jumper at X2 X3 I'm sure it can accommodate the system bonding jumper.

You can ground the secondary anywhere up to the first disconnect if the transformer can does not provide space for the common grounding busbar. System bonding jumper could extend with the load side wiring to the first disconnect.

Bringing the 480 close to the load with the local step down transformer is a smart play, especially if you already have the transformer.

 

[Another C10]

You might be better off putting the lower voltage transformer over by the new loads.

I did plan on that as well, although I changed up my game plan with eliminating a closer 3 phase 277/480 source and go with the undersized 120/240 system 40' further. As noted on my drawing below.


Thank you everyone that contributed to this question, I normally don't ask for input on my designs, but there are many variables involved which is why I posted it here. It's been a long time that I've had the opportunity to ask a large number of qualified electricians on doubts I may have regarding an installation to bid.

Thank you Again.

 

[JoeStillman]

Why wouldn't you just connect X2 and X3 and then ground them? X2-X3 would be your neutral point.

 

[Another C10]

Why wouldn't you just connect X2 and X3 and then ground them? X2-X3 would be your neutral point.

I could, although Id still need the buck boost transformers I believe, because the stepped down voltage will still drop down below a safe level after 300-400 ft. its a tough call on which scenario really is more cost effective.

Either I go with the step down Transformer with new 120/208 panel and the required bonding involved or
go with a Transformer upgrade from 7kva to 15kva utilizing the existing bonding methods and then utilize the existing panel
with the necessary voltage present.

 

[suemarkp]

Buck/boost only works if your loads are constant or nearly so. If some of those upstream loads could be off, you won't have as much voltage drop and could have an over voltage condition.