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  1. mikeengurs

    Building Lighting requirement

    Thanks everyone!
  2. mikeengurs

    Building Lighting requirement

    We are trying to determine lighting requirement for a small process building. Is there a quick way to help determine wattage requirement per square footage? What about celling height? Thanks!
  3. mikeengurs

    MV cable in LV Duct Bank

    Thanks a lot hdp, and Elecband!
  4. mikeengurs

    MV cable in LV Duct Bank

    We have a situation where we have to route MV (4160v) cable in a LV duct Bank. Routing will involve Man Holes where LV and MV will be exiting PVC conduits and entering others as they head to their destination. MV cables are all shielded, with shields grounded on both sides. My question is, when...
  5. mikeengurs

    Load Flow Study

    I'm planning to add motor loads to an MCC fed from a 4160v swicthgear. For that, I'd like to to run a load flow and short circuit analysis to see if existing system can handle it. Both existing swicthgear and MCC have existing motor loads on them. My question is, if the plant gives me short...
  6. mikeengurs

    Phase VA contribution

    That makes sense! I failed to recognize the fact that Real power is also a vector! Thanks everyone for teh help!
  7. mikeengurs

    Phase VA contribution

    ...means, the Line current, which is equivelant to the phase current in this case = 1581/208= 7.6A. Now, if both Transformers (A & C) are seeing 7.6*120=912VA, this means that the total power supplied = 912*2=1824. This doesn't make sense, because the load is only drawing 1581VA. There is...
  8. mikeengurs

    Phase VA contribution

    ...that I'd like to supply with a 2-pole 208v supply (Vac). I understand that a current of 7.6A would be seen by phases A and C. What does that mean VA wise to each phase? In other words, would each phase's load be 1581/2? Or that should follow the phase power equation: S=Vpahse*Iphase = 120*7.6?
  9. mikeengurs

    Transformer Tap settings

    Thank you guys...that was helpful!
  10. mikeengurs

    Transformer Tap settings

    Thanks for the reply. I guuess what I was trying to ask is, what is usually the bus voltage range recommended by standards?
  11. mikeengurs

    Transformer Tap settings

    Electrical system study with all loads connected showed we need to modify primary Taps to -5% to maintain voltage. Currently, most of the loads are not connected, and bus voltages at MV level is around 4300v. If Taps are changed now, voltages might get over 4500v, which is high. First, would a...
  12. mikeengurs

    Equipment grounding size

    Thanks everyone. As allways, this site is very helpful.
  13. mikeengurs

    Equipment grounding size

    Thanks everyone. Since I have 2 parallel #500 MCM, I can have 2-1/0 for each set correct?
  14. mikeengurs

    Equipment grounding size

    Good point 7anoter4. dpc, do you know which NEC requirement is applicable with this? 250.122 talks about using the upstream overcurrent protector as guidance, but this is not present here.
  15. mikeengurs

    Equipment grounding size

    they have a 50:5A ground CT, so the ground current can't be that large. So there is no code requirement for this?
  16. mikeengurs

    Equipment grounding size

    I'm feeding a 1200A MV breaker directly from the secondary side of a 69K/4.16K transformer. I'm using 6 1/C #500 MCM (2 conductors per phase). Table 250.122 in NEC-2011 indicates a ground size of 3/0 if overcurrent device protecting cables is 1200A. In this case, there is no overcurrent device...
  17. mikeengurs

    CO-9 over current relay

    Thanks guys! Basler replacement relays are good options. Is there an advantage of using new relays, instead of just adding an external time delay elements (other than much more features maybe)?
  18. mikeengurs

    CO-9 over current relay

    I have a feeder with CO-9 relay I'd like to coordinate with downstream breakers. The time delay element is adjustable, but the instantaneous element (IIT) is the problem. Does anyone know if we can add a timer to the IIT element? How is that done?
  19. mikeengurs

    Equipment Ground

    All Panels, Tray, and Switchgear are in the same room, and connected to the same ground ring. The switchgear bus is connected to the ground ring by a large 500 MCM cable, so the ground ring will be the effective ground path back to the source panel. Would that be sufficient?
  20. mikeengurs

    Equipment Ground

    I have a switchgear cubical with a ground bus. The case is all grounded through the ground bar. The bar is connected to a local ground, and the 4160v feeder ground. We have multiple power circuits terminating in the switchgear, 120VAC, and 125DC. Do I have to pull a ground cable and terminate it...

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