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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.

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

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...

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.

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...

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...

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...

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...

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.

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...

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...

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...

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...

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

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...

In a few days, I will be performing a forensic inspection of a PV system at a residential property. It was installed 12 to 18 months ago. The power production data of each panel is accessible by both the homeowner and the contractor who installed the system, which leads me to believe that a...

The building is part residential, part commercial (think of a dormitory building or a hotel). It's also approximately 10,000 square feet, so it's fairly small (to me, anyways). Unfortunately, we are limited to reusing an existing electrical room. No opportunities exist for the expansion or...

I am involved in a project in which an existing building is being stripped and renovated in its entirety. Its incoming utility service is 480V, corner-grounded delta. As the project is presently designed, we are stepping this down to 208/120Y and serving all of the building's loads via the...

I've worked on a few projects that contained baffle ceiling systems with EMT conduits located above. We were instructed by the architect to include verbiage on our drawings that required the conduits to be painted black. The projects were located in a rather stringent part of the United States...

There is a free website that can be used for plotting trip curves. A friend of mine had used it for a power systems course that he was taking during undergrad. It was very limited in functionality, though. You will probably need SKM, ETAP, or something similar for the purpose of plotting...