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  1. CHDean

    MCCB vs ACB

    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...
  2. CHDean

    Delta Secondary Ground Fault Indication Req'd?

    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.
  3. CHDean

    Delta Secondary Ground Fault Indication Req'd?

    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...
  4. CHDean

    replacing panel board interiors

    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...
  5. CHDean

    IMC

    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.
  6. CHDean

    fuses

    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...
  7. CHDean

    Ratings on double-ended switchgear

    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...
  8. CHDean

    PANEL SIDE FED MAIN BREAKERS

    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
  9. CHDean

    Best Motor Starting Contactor/Starter

    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...
  10. CHDean

    My house has intermitant power brow

    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.
  11. CHDean

    Overvoltage conditions damaging VFD's

    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?
  12. CHDean

    Power Factor Capacitor Failures

    PFC's and VFD's don't go together. Two options, remove the PFC's or put harmonic filtering in front of them (can be expensive)
  13. CHDean

    GFI for non-standard voltage

    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.
  14. CHDean

    Power Factor Capacitor Failures

    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...
  15. CHDean

    New Cutler Hammer Motor Control Centers

    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...
  16. CHDean

    MCC Location

    No rules apply other than common sense. Ideal MCC placement is close to loads but in an area protected from physical damage. The other consideration is ambient thermal conditions and contaminants. Heat, dirt,moisture, and airborne chemicals can shorten life and promote faults/failures. If...
  17. CHDean

    Square D panelboard

    A 100A QOB should fit but you'd be using as a disconnect only as upstream device would react first in most situations. If you use a smaller breaker you should acheive a better degree of coordination. Without knowing loading, 60A would seem reasonable.
  18. CHDean

    Square D panelboard

    Absolutely, a sub-panel is definitely a solution. You will need to determine the total connected load of the existing panel to determine how much room is left for additional loads. The panel you have will accept up to a 100A branch breaker to feed the sub-panel, you may need to relocate some...
  19. CHDean

    Square D panelboard

    No, tandems are a residential device only. That's why you see loadcenters with multiple circuit designations like 12/24 or 16/32. The higher circuit density is obtained with CTL type tandem breakers. Lighting panelboards such as the NQOD/NQOB are strictly limited to the number of circuits they...
  20. CHDean

    Convert KWH Metered Consumption to Peak KW Demand

    With just consumption data I think it's pretty much impossible to extrapolate a peak demand. Peak demand is measured in windows of time. In a residential setting demand will swing with time of day and season due to heating/cooling loads or lack there of. Even in industrial systems new peaks...

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