location of transformer for computer server room.

[steve61]

I am installing a circuit in my place of work to have the computer server room hooked up to an emergency generator. I will be using a 15 KVA transformer to step the voltage down from 460 VAC to 208 VAC. The circuit will be about 450 feet long from the generator panel to the server room. Can I locate the transformer at the generator panel,Or do I have to have the transformer located closer to or in the server room ? Also,Do I need to install a ground rod for the transformer ? Thank You for any info. Thanks,Steve Wiese.

 

[infinity]

For that length you would want the transformer at the end not at the beginning so that your 450' of circuiting would be at 480 volts. That solves two problems one it lowers the voltage drop and secondly you can run smaller conductors at the higher voltage.

 

[steve61]

I already ran # 8 wire for that circuit. Maybe I could still install the transformer at the beginning of the run ? It would make it easier since I have very limited room in the server room.

 

[LarryFine]

You want the bulk of the distance to be at the highest voltage.

That's how the power companies do it.

 

[infinity]

I already ran # 8 wire for that circuit. Maybe I could still install the transformer at the beginning of the run ? It would make it easier since I have very limited room in the server room.

What the load on the transformer secondary? I used the Southwire VD calculator with 25 amps of load and came up with a minimum conductor size of #4.

Voltage Drop​

Minimum Conductor Size​

2.79%​

4 AWG

1 conductor per phase utilizing a 4 AWG copper conductor installed Cable, Conduit (non-Steel), & Direct Burial will limit the voltage drop to 2.79% or less when supplying 25 amps for 450 feet on a 208 volt three phase system.

 

[augie47]

As for your question on grounding, the transformer secondary should be bonded and connected to the building grounding electrode system.
You should review 250.30 for grounding, SBJ and SSBJ