Xylem’s HVAC solution for the tallest building on the West Coast

Xylem’s HVAC solution for the tallest building on the West Coast

The new Wilshire Grand Center in Los Angeles, opened in 2017, is the tallest building west of Chicago. Safety and sustainability were central to the design of 73-story skyscraper, which is why Xylem’s innovative Bell & Gossett and A-C Fire Pump products were selected for the HVAC and fire protection systems.

The lower seven stories of the 1,100-ft.-tall Wilshire Grand Center, a podium structure, house shops, restaurants, meeting rooms, ballrooms and a swimming pool. On top of this is 400,000 square feet of office space. The reinforced concrete core of the building provides earthquake and fire protection, while radiant heating and cooling systems use a fraction of the energy of a forced-air system.

A high-efficiency HVAC system

An HVAC system can account for as much as 50 percent of a commercial building’s energy use. ACCO Engineered Systems designed the building’s hydronic HVAC system, working with AC Martin and general contractor Turner Construction Co.

The HVAC system has now achieved LEED-Gold status. It features a central plant with high-efficiency chillers and condensing boilers that supply chilled and hot water to the 2.1-million-square-foot building.

Relying on its longstanding relationship with Dawson Co., a Bell & Gossett manufacturer’s representative, ACCO specified Bell & Gossett pumps and products for the Wilshire Grand’s HVAC system.

“A major challenge on the project was that construction had to begin prior to completion of the design – and the budget was already set,” said John Boncich, Senior Vice President, ACCO Engineered Systems. “We knew support from the Dawson and Bell & Gossett teams would be important from a technical standpoint and also in meeting critical milestone dates.”

Heating and cooling for restaurants, office space and a hotel

Bell & Gossett’s 300-psig working pressure VSX and e-1510 pumps supply chilled and hot water to the lower podium and office levels. Standard working pressure VSX pumps serve the thermal energy storage system (TES) on the podium’s second level. The TES charges a large water tank overnight to reduce the number of chillers needed to operate the building during the day.

“Besides the versatility and robustness the VSX brings to a high-efficiency hydronic system, it’s easily serviceable and its compact design takes up less space in the pump room,” said Manual Masso, Dawson Co. Vice President of Commercial Sales. “Decreasing the size of mechanical rooms means more saleable space, and that’s a priority in all commercial building projects.”

Bell & Gossett AHRI 400 certified plate-and-frame heat exchangers isolate the building’s pressure zones from each other. Other Bell & Gossett equipment for the HVAC system includes air separators and expansion tanks that increase and decrease pressures in the hydronic system in response to changes in building temperature.

The Intercontinental Los Angeles Downtown hotel occupies about 900 rooms on floors 31 to 66, plus bars and restaurants on floors 69 and 71. Inside the mechanical room on the 30th floor, 300-psig VSX pumps provide climate comfort to the hotel guest rooms using four-pipe fan-coil units and air handlers.

B&G series e-90 inline pumps, designed specifically for commercial hydronic systems, provide radiant floor heating and cooling in the ground-floor lobby and in the sky lobbies.

A-C Fire Pump’s plan for meeting stringent codes

The roof design is one of the most talked-about features of the Wilshire Grand Center. It breaks with L.A.’s traditionally flat-roofed skyscrapers that are required to have helipads by city code.

Wilshire Grand architects obtained an exemption from this rule because of the addition of other fire safety features that would exceed the city’s fire-code requirements, such as the reinforced concrete central core that contains a staircase solely for the use of firefighters in the event of an emergency.

Stringent L.A. and California building codes for fire safety and the NFPA 20 Standard for the Installation of Stationary Pumps for Fire Protection—as well as project parameters—drove the design process.

“One of the challenges was to design a system that met the city of L.A.’s requirement that total pressure shutoff can’t exceed 600 psi,” said Brian Buscher, Global Product Manager for Fire Protection, Xylem AWS. “Our A-C Fire Pump distributor, Starfire Inc., worked closely with sprinkler contractor XL Fire Protection on the design.”

Brian Callahan, president of XL Fire Protection, accredited Certified Fire Protection Specialist (CFPS) by NFPA and level 4 certified NICET designer, sketched out a two-zone system. He ensured the system met the requirements for the high rise, worked within the space restraints of the fire pump room, and did not exceed maximum pressure requirements.

“One pump services the low zone, but the high-zone portion requires two pumps in series to create the 600 psi that was required,” said Starfire’s Paul Bennett. “Once I knew the flow and pressure requirements, I was able to select the right combination of pumps to achieve that result.”

A-C Fire Pump vertical-turbine pumps and A-C Fire Pump 8200 series horizontal split-case pumps were selected for the job. Codes require an exact set of redundant fire pumps on each level, so that meant six fire pumps in total.

“By getting the number of pumps down to six, there was no need for an additional emergency generator, which saved project costs,” Callahan explained.

The challenge of controlling the fire pump pressure

Once the design was conceived, the team had to be sure the system would work as planned.

“We had to do a lot of sizing and theoretical planning on what the pump curves would look like, especially in the high zone where the vertical turbines pump into the split-case pumps and were approaching 600 psi,” Bennett said.

That also becomes more complicated because of NFPA 20 requirements for fire-pump impellers, which state the pressure at shutoff cannot exceed 140% of the rated pressure at the rated flow and can’t be below 65% at 150% of the rated flow.

“One of the things we look at is not just the design-point flow and head-system needs, but also what the pressure is on the pump when it is at churn,” Buscher said. “We have to design the impeller to limit that pressure so that it is not over pressurizing the system components downstream of the pump.”

Even at shutoff, the static pressure in the turbine pumps was 77 psi, which required a pressure-reducing valve on the standpipe systems. “Controlling the pressure was our biggest challenge,” Callahan said.

The Wilshire Grand fire-protection system design is also unique in the low-zone pump room, with the vertical turbines sitting atop a 120,000-gallon, three-story water tank in the second of five basement levels. With space at a premium on the site, there was no room for it outside the building. Designers had to be sure this setup would meet the NFPA 20 requirement on how tanks are constructed and that the fire pump would be capable of providing demand for the whole building in an emergency.

Testing and training after construction

Once HVAC and fire-protection systems were in place, the next steps were to test the systems and train building personnel on their operation. On the HVAC side, Dawson Co. representatives conducted equipment training for maintenance and other personnel on the 18 Bell & Gossett products prior to the building opening.

“In the end, everything worked as designed,” Callahan said. “It’s not just putting in products; everything had to perform properly as a system and meet code.”

de către Chad Henderson