Ground fault / Separately derived systems 1

[sgc]

Greetings,

I have a Topaz Line noise Ultra Isolator 15KVA 208Y/120 in, 208Y/120
output supplying our computer center. Some of the UPS's and surge
protectors are indicating a ground fault condition. We are reading a
voltage of 16 volts across the neutral and the equipment ground. This 16
volts are from some phase imballance and some electronic injection I am
sure. If we install a jumper wire between the neutral and equipment
grounding bus the fault condition lights go out and the voltage drops to .0
levels.
My question, is it acceptable to bond the equipment grounding bus and
the neutral bus together in the breaker panel that is served from the
isolation transformer?
This gets back to the question of connecting the equipment ground and
the neutral buss bars together at other than the service entrance panel.
I am of the opinion that the isolation transformer is a separately derived
system and is permissable to bond the equipment ground and the neutral
busses together being as how it is the first panel to be served from the
"new system". Am I interpreting this right and is this the intent of the
NEC? If not then what should I do to clear the fault condition?
SGC

 

[resqcapt19]

Not only is this acceptable, but requried by 250.30(A)(1). This is assuming that there is not a bond between the grounded and grounding conductors at the output of the UPS, as this bond is only permitted at one location.
Don

 

[RajT]

It is perfectly acceptable and logical to bond the N and the ground bus (in the equipment)noting that the N at the transformer is further grounded somewhere on the plant/building main earth/ground

 

[sgc]

Thank you resqcapt19 & RajT for the timely and informative responce.
This is my first visit to Eng-Tips and I can see I have tapped into a wealth of knowledge that I certainly will be viewing and using.
Keep up the good work!
SGC