My current job has a Square D 1600A QED switchboard for a main with a GC-200 ground fault interupter.
The other day the entire building tripped off line interupting all the trades while we got things reset. I found out that the GFI comes from the factory set to the minimum trip point and I didn't know enough to adjust it at the time of installation.
I will get the desired trip point from the engineer, but I was wondering if anyone can walk me though this adjustment. The Square D rep said that it would be calibrated in amps or as a percentage. Thats about all I know. Any insight would be helpful.
Not Sq D equipment, but a couple of years ago had 4000A Switch, Fused at 3400Amps, 480 3Ø 4W system on a building I was inspecting.
It seemed the Contractor and the and the Engineering testing Company were not very co-operative in the 230-95(c) department.
The sensor was a donut around the neutral bus.
The Service was 10 parallel sets of 500Kcmil with 5 sets landed on one side of the donut and and the other 5 sets on the same side of the donut as the bus connection into the next compartment. Quite an ordeal to have the donut moved between the 10 neutrals and the bus connection to the next compartment as indicated by the one-line diagram for that Service Equipment.
After the sensor was relocated, twice that I know of, a line to ground short on a 4AWG circuit some 300' away from the 45 Amp fused switch in the switchgear 'line-up' tripped the 4000A GFI .
[This message has been edited by Gwz (edited 06-04-2003).]