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case study
California Penthouse:
VRF Zoning System
Solves 15-Year-Old
Comfort Challenge
San Diego, California
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.
Brue-Carstens Residence
Project Location:
San Diego, California
Completion Date:
September 2012
Project Team
Owners:
Sandra Brue and Chris Carstens,
San Diego, California
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 Watersource 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
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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, fourpipe water-source system was not suited to
the home.
Challenge
Finding a versatile, efficient HVAC system
that could provide residents with comfort in
problem zones and supply simultaneous
cooling and heating.
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 INVERTERdriven 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 WR2Series VRF zoning system. The Sirius team
November 2014
case study
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.
Solution
A WR2-Series VRF zoning system provided
balanced comfort and just the right amount of
cooling or heating.
The team next designed a mostly ductless
solution for the penthouse using ceilingrecessed 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.”
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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