A major difference is that most MCCB are designed with a "Blow Open" contact arrangement. The magnetic forces caused by rapid rise of current actually aid in the opening of the contacts under fault conditions, the higher the current the stronger the repulsion. This is why there is no...
A zig-zag with a pulsing circuit can be a great troubleshooting tool. They use a snap around ammeter with about a six inch window to trace the fault down. But like most things that work they aren't cheap. Good luck.
Not required but not a bad idea. NEC 230-95 requires ground fault on WYE systems =/+ 150V to ground but not over 600V phase to phase. This only applies to service entrance applications for each disconnect of 1000A or more.
A ground fault indicating light system would be a relatively...
UL labeling is a sticky subject. I have retrofitted panelboards into existing tubs many times. I have yet to have AHJ question the validity of UL labeling, normally they are worried about bending radius of feeders. I would use the fact that the steel exceeds NEMA standard and most likely all...
The I in IMC is intermediate, not rigid but not EMT. It uses fittings like rigid conduit but has reduced wall thickness. Personally I think it works well for most industrial environments, the exception being extremely harsh chemical environments where even rigid should have a PVC jacket.
You stated that the failures are occuring on the supply side. Are we to assume that you are melting the fuseholders or fuse body itself? If this is the case there are a couple of things to look at. 1.) You may have lost the spring tension in the fuseholders causing high resistance connection...
Considering the loads you have, double ending as 100% back-up is not a good idea. At 3400A per side you can't even get a standard breaker/fusible switch to use for the mains or tie as each could be loaded to 6800 in a disaster. The best you're going to do is a 5000A DE substation and I...
Normally not a problem, exception would be electronic trip breakers not designed for back feed. UL and NEC just require a mechanical attachment to prevent unintentional removal of energised breaker
ScottyUK,
All three breakers are the same as you observed. AB and Siemens AG have both bought Westinghouse/Cutler Hammer breakers for many years. Brand labeling for AB started earlier this year, I think they only sold replacements previously. As a former employee of Siemens in the US I never...
Does the weather affect it? (windy conditions, T-storms)
It sounds like a loose connection or possible intermitant loss of neutral, all of which are most likely utility related.
You may want to look at transient voltage surge suppression if you're sure it's voltage related. Do you have any impedance in front of the drives now? Also, are the 5HP units rated 440 or 460V?
A standard US made GFCI breaker most likely will not function below 107VAC. The internal electronics will become unreliable and at some point not operate.
With the limited data you've supplied two things jump out at me. 1.) Are there drives or other harmonic generating devices in the system and if so how bad is it?
2.) If caps are floating are you going into a lead when the air handlers aren't running and maybe causing high voltage condition. If...
To expand on Richanton's comments about communications.
There are two communications methods. A.) individual devicenet to the starter or B.) QC port which daisey chains the starters together back to an I/O block that converts to devicenet. This allows you to use one node rather than a node per...
