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Recent content by jmbelectrical

  1. jmbelectrical

    Arcing fault at 480/277V panelboard, overcurrent protection, and grounding

    My apologies for the delayed response. For those who asked: 1. The transformer's secondary is 480/277V, wye-connected, solidly grounded. 2. The transformer's impedance is 4.48%. 3. The fuses are 400A, dual-element time delay type, Trionic TRS400R.
  2. jmbelectrical

    Arcing fault at 480/277V panelboard, overcurrent protection, and grounding

    wayne440, Clear. Weather data did not indicate the presence of lightning both on the date of the incident and several days prior.
  3. jmbelectrical

    Arcing fault at 480/277V panelboard, overcurrent protection, and grounding

    I am investigating an incident in which a failure, resulting in a fire, occurred at a 480/277V, three-phase, four-wire panelboard. I do not know the causation of the failure at this time, however, I know that arcing occurred at some point due to the presence of irregularly-shaped openings along...
  4. jmbelectrical

    High voltage on utility transformer secondary

    This was a sustained condition. The property owner does not reside at the house full-time, so its exact duration is unknown. The overvoltage condition was initially discovered by a technician who was in the process of replacing a pool pump.
  5. jmbelectrical

    High voltage on utility transformer secondary

    A house is supplied with a 240/120-volt, single-phase, three-wire service. No other houses are connected to the utility transformer's secondary side. The property owner is alleging that their phase-to-phase voltage rose to between 270 and 280 volts, resulting in the failure of numerous items...
  6. jmbelectrical

    Elevator Controller SCCRs

    Elevator manufacturer A has indicated that their elevator controllers have an SCCR of 5,000A, with no options for a higher SCCR. Elevator manufacturer B has indicated that their elevator controllers have an SCCR of 10,000A, with greater SCCRs (14,000A at 600V, 25,000A at 480V, and 45,000A at...
  7. jmbelectrical

    Need more $$$, thinking about changing careers or doing side work.

    You should consider a career change to forensic engineering. As a mechanical PE with seven years of design experience, you would be considered qualified by most forensic engineering firms. While the salaries are only marginally better than those in MEP consulting engineering, the work schedule...
  8. jmbelectrical

    HVAC Equipment and Phase Loss

    In a few days, I will be performing an inspection at a property that reportedly suffered from phase loss, followed by damage to three-phase HVAC equipment. At this time, I'm not sure if damages involve air handling units, condensing units, packaged rooftop units, chillers, pumps, or a...
  9. jmbelectrical

    Two HVAC chillers with VFD failures and compressor failures

    Keith, Thank you for the response. It was extremely helpful. Do you happen to know of any whitepapers or other authoritative literature that addresses the average lifespan of a modern VFD? Everything I've found so far has been anecdotal. Thanks again.
  10. jmbelectrical

    Two HVAC chillers with VFD failures and compressor failures

    In a few days, I will be inspecting two HVAC chillers. They are arranged in an n+1 configuration in which only one chiller operates at a time. They are estimated to be approximately 15 years old. I do not know if the chillers are located outdoors or indoors. With respect to the VFDs, I do not...
  11. jmbelectrical

    Generator Exhaust Gas Temperature vs. Load

    A mechanical engineer presented to me a specification sheet of a 2.5MW, medium-voltage, natural gas generator. The engine appears to be turbocharged and combustion is classified as "low emission." He is interested in the temperature of the exhaust gases as a function of load. The specification...
  12. jmbelectrical

    Generator and grid-tie PV system

    I will be performing an inspection at a residential property next week. The electrical service is 240/120-volt, single-phase, three-wire, 60Hz. It is equipped with a 60kW, whole-house, standby generator and a 13kW PV system. The PV system connects to a loadcenter/panel via a grid-tie inverter...
  13. jmbelectrical

    Transformer Failure Resulting in Overvoltage

    A 240/120V, three-phase, four-wire, delta high-leg system comprised of three (closed delta) pole-mounted transformers serves two commercial properties. One of the transformers presumably failed, resulting in the opening of its primary-side fuse cutout. Both properties allegedly suffered from...
  14. jmbelectrical

    PV System Failure

    Palletjack, This is the paper that I was referring to: https://engineering.case.edu/centers/sdle/sites/engineering.case.edu.centers.sdle/files/iea-pvps_t13-01_2014_review_of_failures_of_photovoltaic_modules_final.pdf
  15. jmbelectrical

    PV System Failure

    It wasn't that one. The paper that I found was in PDF format. I believe it was dated 2014. I'll try to dig it up on my work laptop. The property is located in the southeast United States. It's in a high lightning activity region. We are required to pull lightning activity and weather data...
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