To seperately dervive or not

[dragonlp]

I am installing a 36kw 3ph generator as an optional system. The generator
is trailer mounted. I am trying to decided if there is any advantage to go
with a seperately derived system over a nonseperately derived system. My
inspector does not have a preferance. I have read Stallcup's generator book
and understand the difference between the systems, but would like to know
if one has any advantages.

Thank you for any opinions

Steve

 

[benaround]

dragonlp,

So the generator has a choise of voltages?

 

[dragonlp]

I will be using 120/208. Mostly 3ph loads for refridgeration equip.

Steve

 

[tom baker]

A separatly derived generator is determined by the transfer switch, the generator will have a system bonding jumper, grounding electrodes and the neutral will be transferred. This type of system is installed by design
More commonly is a non separatly derived generator, no system bonding jumper, no ground rods and the neutral must not be transferred.
A SDS generator is required with services over 1200 A and ground fault sensing.
See definition of SDS and 250.32

 

[LarryFine]

Steve, in other words the non-SDS system is cheaper and easier to install.

 

[tom baker]

But, if you use the same generator for a Steves Carnival And Electrical Show, then its a SDS, ground rods and system bonding jumper required. There is no standard on portable generators if a system bonding jumper is installed from the mfg. You must open it up and look.
However the smaller 5 kw types with receptacles seem to have a system bonding jumper. In any event the system bonding jumper is what allows the fault current back to the generator windings.

 

[dragonlp]

Thank you for your replies.

Steve

 

[dereckbc]

but would like to know
if one has any advantages.

Both have advantages. For your application non-SDS is the way to go, it is less expensive.

SDS applications have to be used for services over 1200-amps, and should be used on sensitive electronic equipment like communications and data centers. SDS should also be used when any Ground Fault Relay Protection is involved in any of the switch gear to prevent false trips.