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  1. SierraJ

    Power Recorder Reading - 5 Elevator Bank

    I am planning on having the meter re-certfied just in case. However on that same line of thought, could having the flexible Ct's very close to each other inside the wireway have something to do with the strange readings? I tend to discard any problems with the equipment connection, because it...
  2. SierraJ

    Power Recorder Reading - 5 Elevator Bank

    That was my initial impression, with regards to the reading where there was negative real power and negative reactive power at the same time. I thought that the controller is using some type of regenerative breaking system. However, this did not make any sence to me with regards to the...
  3. SierraJ

    Power Recorder Reading - 5 Elevator Bank

    In this case, this is a reading from an existing elevator feeder with existing elevator controls. I would suspect (because I do not have any detail information on the elevator controllers) that this system does not have any type of filter (based on the readings). My initial impression is...
  4. SierraJ

    Power Recorder Reading - 5 Elevator Bank

    Hi, Attached is a short (1-1/2 minutes) table of power mesurements taken at 1 sec. intervals on the main feeder (wireway) for five elevator car disconnects at an existing hospital facility. Being a PE in the design field all my professional career, this power measurements are some what...
  5. SierraJ

    Difference between US 230VAC and UK 240VAC?

    Thank you for the clarification ScottyUK. However, I think we all recognize that there are many differences between the US and UK electrical systems. I only wanted to point out one of the many safety hazards related to the proposed equipment use. Many of the initial posts only addressed the...
  6. SierraJ

    Difference between US 230VAC and UK 240VAC?

    One small detail to consider... From a safety (or code) point of view it will probably be better to buy the equipment as per US standards. Since the US 240VAC system has two(2) 120VAC 'live' wires, the main switch or contator for the equipment must be a 2 pole swith in order to disconnect both...
  7. SierraJ

    cycle transformer power to save energy ?

    Your proposal seems very interesting and besides the usual skepticism for the possible transformer failures (and one could argue about failure to down stream equipment also), I would urge you to make an engineering cost analysis and try it in a limited basis. I think you have an ideal scenario...
  8. SierraJ

    designing a ground grid with a "ground well"

    Look at this link http://www.erico.com/products/GroundGrids.asp from Erico. Jose
  9. SierraJ

    designing a ground grid with a "ground well"

    On our experience, designing for a low ground mat resistance (lets say below 2 ohms) is not that difficult, if enough grid cover area is available. The most problematic parameter is keeping the step and touch voltages within the acceptable limits. We have found that for problematic areas...
  10. SierraJ

    Splicing Shielded MV Cable to Non-Shielded MV Cable

    In addition to the issues already mentioned, you need to remember this will present some safety related issues also. Without proper grounding of the 8kV cable shield, it will act as a capacitor and maintain a dangagerous voltage even when the cable is de-energized.
  11. SierraJ

    system bonding jumper

    The answer is yes, you will have to terminate the equipment grounding conductor for the 480V feeder at one of two locations; 1) the grounding lug at the conduit insulating bushing or 2;) at the ground lug inside the transformer enclosure. However it is very important as you already mentioned...
  12. SierraJ

    Transformer impedance

    It is important to note that the statement "with a nominal 5.75% impedance" clearly indicates that the transformer impedance is provided at the transformer nominal capacity. This means that for any other transformer rating (65°C or cooling fans) you will need to calculate the equivalent...
  13. SierraJ

    Built 120V circuits, now need single phase 208V circuits

    If all the information you provided is correct (the main panel is three phase, the server room panel is 120/208 with two "hots" & one neutral) then you can install new 208V branch circuits to feed the new server from this server room panel. However you need to take make sure that the system has...
  14. SierraJ

    High Voltage Cable Clamps

    I need information on high voltage (115kV) cable clamps for underground manhole installation. These are for supporting the cables to unistrut racks inside prefabricated manholes. They must be either non-metallic or stainless steel (corrosion resistant) Thanks
  15. SierraJ

    PF correction.

    IEEE Standard 141-1993 (Red Book) provides the following aproximate formula to "show the importance of reducing the reactive component of current in order to reduce voltage drop": /\V = R I Cos(Phi) +/- X I Sin(Phi) /\V = (+) for voltage drop and (-) for voltage rise Phi = Power factor angle...
  16. SierraJ

    Information concerning ANNEX 1 (Motor Grounding)

    This should be an easy one, I imagine that the RFQ is refering you to documents that are attached or should have been made part of the document you are reading, like an apendix at the end of the document.
  17. SierraJ

    Electrical Raceways & Equipment - Seismic Restraints

    BJC, Thank you very much for your help, I will try to get the B-Line details. At one moment, I started looking at the SMACNA, used by the mechanical engineers but... I then realized I didn't have that much spare time.
  18. SierraJ

    Electrical Raceways & Equipment - Seismic Restraints

    Does any body knows of any easy reference (application guide, manual, etc.) to perform seismic restraint calculations for electrical receways and equipments?
  19. SierraJ

    Tide power

    I am not an expert but I beleive it should be reasonalble to say that the use of "blades" is the natural solution, since you are trying to harvest water "flow", and the more blade area you provide the more energy you can harvest. This is different than harvesting the energy from a water "head"...
  20. SierraJ

    Power Factor Corection - Diesel Genset

    Thank you everyone, the discussion has been very productive. Altough it has mainly centered arround the leading power factor issue, which was already settled at the first few threads. But for those of you concerned with this issue, we had already confirmed with hystorical "in-house" power...

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