[JPK]

I am working in a temporary building with; 16 offices, 16 A/c units, 4 people per office, computers and printers on every desk, refrigerators and battery back-ups plugged into every outlet available. There is a high load and power provided by a large 40 or 60 KW generator. The entrance panel has been wired through a GFI that constantly trips. When the building was nearly empty it do so as well all though you won't find anyone that remembers. Outside temperature can sore to 130 degrees but mean temps hover around 100-110 at mid day. The main breaker has never tripped and the generator hums along like it runs on air. There seems to be no rime or reason for when the GFI trips although we have determined something is wrong with one suspect circuit. We simply open the breaker #8 when we suspect the fault has been caused by it and reset the GFI and go on with bussness. Questions are:

• Is the generator or its wiring suspect?
• Is the CB #8 suspect?
• If the wiring of CB#8 or any other line improperly installed and undetected cause GFI problem?
• Can all those A/C units, uneven loads, surges in electrical draw cause feedback or surges that would trip a GFI?

[tkrussell]

Good questions, but first more detail is needed please. The questions are very broad or lack values.

My perception is that this is a jobsite moblie office powered only by a generator.

What is:
System Voltage?
System Phase?
Actual KW or KVA of genset?
Genset fuel?

Describe the GFI, are there adjustment dials or settings on the front? Sometimes hidden for protection of dials, behind a door or cover but usually is a label indicating their location.

Size of main breaker?Is this part of the GFI?

Size/style of AC units? Ducted or Split-system/ductless system?

Qty and KW/KVA of UPS Battery Backup units?
This plus the amount of PC's, create a large capacitive load that does not do well on generators. This lead factor is helped by the amount of AC units inductive load, but worth checking to be sure not a contributor to the problem.

Are there any transformers or PDU units?

Any and size of surge protectors at any main switch or breaker panel?

What does breaker #8 feed?

Is this a Disaster Recovery Site?

I am wondering if this GFI is a relay style, or builtin in option to a large molded case breaker, that is adjustable but set at it's lowest settings, and the fact that refrigeration compressors do not do well on GFI, due to inherent leakage current, then add the capcitive load of the UPS/PC load, it's a wonder the system runs at all.

Only kidding, but seriously the system is being stressed, but may only need a minor adjustment if everything is in "balance". GIve me what you can and we can go from there.

Oh if you do find adjustments on the GFI, don't change anything, depending on the organization this belongs to, may need the settings furnished by the engineer-in-charge for the project.