case study

www.mitsubishipro.com November 2014

California Penthouse: VRF Zoning System Solves 15-Year-Old Comfort Challenge

San Diego, California

Brue-Carstens ResidenceProject Location: San Diego, California

Completion Date: September 2012

Project Team

Owners: Sandra Brue and Chris Carstens

HVAC Contractor: Sirius Mechanical, Inc., Moreno Valley, California

HVAC Distributor: U.S. Air Conditioning Distributors, City of Industry, California

Mitsubishi Electric Equipment Installed:

(2) PQRY-P96THMU-A WR2-Series Water-source Condenser Units

(2) PLFY-P24NBMU-E Ceiling-recessed Indoor Units

(2) PLFY-P18NBMU-E Ceiling-recessed Indoor Units

(6) PMFY-P12NBMU-E Ceiling-recessed Indoor Units

(1) PEFY-P15NBMU-E Ceiling-concealed Ducted Indoor Unit

(1) PEFY-P08NBMU-E Ceiling-concealed Ducted Indoor Unit

(10) PAR-30MAAU MA Controllers

(1) CMB P1013NU-GA BC Controller

(1) GB-24A Centralized Controller

The homeowners soon found, though, that the towering windows created not just stunning views but also frequent challenges in cooling and heating their home. The peak solar energy from the San Diego sun and a mild winter climate both meant that rooms on the home’s south side got very warm and required air conditioning. “On a typical 70-degree day in San Diego,” Brue said, “if we had our HVAC system turned off in rooms facing south and west, room temperatures could easily climb to 100 degrees.” There were even heating disparities within the same room.

The couple struggled for more than 12 years to find a system that would solve their complex zoning issues. They installed two different HVAC systems, and “the last, local HVAC firm we were using said the job was just too complex for them,” Carstens said. That firm recommended going directly to Mitsubishi Electric US Cooling & Heating Division (Mitsubishi Electric), who in turn recommended Sirius Mechanical, Inc. (Sirius), Moreno Valley, California.

Randy Scholnick, Sirius director of sales and Sirius Chief Executive Officer Case Bennett visited the penthouse and discovered something huge: The existing 16-ton, four-pipe water-source system was not suited to the home.

In 1997, Sandra Brue and husband Chris Carstens renovated a 3,700-square-foot penthouse in one of San Diego’s tallest towers. Its soaring windows looked out 360 degrees over the city, offering sweeping views of Coronado Island and the Pacific Ocean.

The Sirius team recommended a Variable Refrigerant Flow (VRF) zoning system from Mitsubishi Electric. Building restrictions prohibited condensers on the rooftop, so they selected the brand’s water-source WR2-Series VRF zoning system, which features condensers that can be placed indoors. The system could also couple with the existing geothermal loop. The WR2-Series can cool one zone while heating another and features an INVERTER-driven compressor for outstanding performance and optimized energy usage.

Scholnick explained that the Mitsubishi Electric VRF zoning system would provide precise comfort where all other systems had failed; its ability to simultaneously cool and heat, as well as the ability to use a remote controller in each room connected to a centralized controller, would be the answer the couple so direly needed.

Brue and Carstens agreed to try the WR2-Series VRF zoning system. The Sirius team

ChallengeFinding a versatile, efficient HVAC system that could provide residents with comfort in problem zones and supply simultaneous cooling and heating.

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removed the old system and found they were able to take out a portion of an unused wall in the mechanical closet. This created space in which the Sirius team could install the two 8-ton heat pumps.

The team next designed a mostly ductless solution for the penthouse using ceiling-recessed indoor units. The old massive ductwork and register grills from the original system were no longer necessary, creating four to six additional inches of ceiling height. The added space provided the home with more visibility and an even roomier feel.

“This is the first time we have had a completely working system in 15 years,” Brue said. “This technology is remarkable. Its excellent sensors are able to compensate for the huge heat gains and losses and give us comfort. It provides cooling or heating wherever and whenever we need it. The system is easy to handle. Now, we preset our air-conditioning timing. We simply press a button; it is so easy to change. We can even control the unit from our smart phones! We love our home.”

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SolutionA WR2-Series VRF zoning system provided balanced comfort and just the right amount of cooling or heating.

The old systems never worked properly to overcome the formidable heat gain,” said Carstens. “The decision to go with a Variable Refrigerant Flow [VRF] zoning system from Mitsubishi Electric made all the difference. This technology is remarkable.”

The couple’s original HVAC system required massive ductwork. The VRF zoning system did not. Removing the ductwork created four to six additional inches of ceiling height throughout the home, providing an even more spacious interior.

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