Emergency Generator Replacement at 3401 Walnut

As a subconsultant to Atkin Olshin Schade, Trefz Engineering was brought in to solve a problem that had no easy answer: an aging emergency generator in a dense urban building needed to be replaced, but the existing basement location couldn’t accommodate it. Trefz was tasked with engineering a solution that satisfied complex code requirements, kept the building fully operational throughout construction, and addressed the full mechanical and fuel system challenges of rooftop generator placement.

The Scope

The building’s existing emergency generator had reached the end of its useful life. A larger replacement was needed to support life safety and critical standby systems, but space constraints below grade and no available footprint at street level made a conventional replacement impossible. Trefz engineered a rooftop installation as the solution.

Beyond the generator itself, the project required a complete fuel oil transfer system spanning the full height of the building: a filling station at grade, a day tank in the basement, and a pump lifting station to supply the rooftop belly tank. The fuel room was also fitted with a foam-water sprinkler system.

The Process

Trefz developed a phased plan to maintain emergency power coverage throughout construction. The existing generator was removed and a temporary unit connected in its place while the permanent 80kW / 480V diesel system was installed and commissioned on the roof, ensuring no gap in coverage for life safety systems at any point.

The rooftop location required the fuel oil transfer system to comply with the International Building, Fire, and Mechanical Codes, NFPA, and FM Global standards. Trefz also coordinated this scope alongside a concurrent campus upgrade that transitioned the building from its existing condenser water system to a district chilled water network.

The Result

The completed 80kW rooftop emergency generator system exceeded applicable code requirements and gave the building a modernized emergency power infrastructure designed for long-term reliability. Careful phasing kept operations uninterrupted from start to finish, and the building moved into the broader campus district chilled water upgrade with its electrical foundation already in place.

Let’s Collaborate

Trefz brings a construction-minded approach to complex mechanical, electrical, and plumbing challenges across every project phase. If you have a project in the works, we’d love to hear about it.