Bristol, CT - Historic Site

The Challenge

• Retrofit a 130,000 square foot office building (originally constructed as a manufacturing site circa 1919) with state-of-the-art HVAC equipment and controls to improve health, maintenance, and energy use.
• Phase and coordinate construction so the building can remain fully occupied and keep the occupants comfortable

The building, located in Bristol, CT, was outfitted with water source heat pumps and fan coil units throughout, served by cooling towers and boilers. While the building worked relatively well in terms of maintaining temperature, the distributed mechanical equipment created an intensive maintenance load, and the poor ventilation resulting from the system design caused health concerns that needed to be rectified.

The Players

The primary building occupant, one of the leading providers of employee life and health insurance benefits in the United States, requested a heating, ventilation, and air conditioning system and controls that would provide top-notch environmental conditioning, energy savings, and flexibility in terms of scheduling, adjusting setpoints, and problem notification.

Carpenter Companies, the owner of the building and prime contractor for the construction, was primarily concerned with installing a system that would meet the occupant’s needs while providing a less maintenance intensive equipment configuration and cutting-edge technology.

JP Engineering, LLC was the consulting engineering firm hired to design and specify the HVAC solution for the retrofit.

RCMS Controls, Inc. was the controls contractor hired to install Automated Logic Corporation’s (ALC) WebCTRL product as the controls solution of choice.

The Solution

• Excellent selection of and coordination among all members of the design and construction community involved in the project State-of-the-art Automated Logic WebCTRL web-based control system.
• Partial ice thermal storage central plant; all pumps equipped with variable frequency drives, 2-speed fan motors on cooling towers.
• 4 variable air volume (VAV) air handling units (AHUs) with 100% economizer capability and CO2 demand-based ventilation providing conditioned air to VAV boxes throughout the building, perimeter reheat, and crossover dampers with innovative control strategies enabling the system to meet erratic occupancy ventilation and conditioning needs in an energy efficient manner.

The Story

JP Engineering initially recommended a central partial ice thermal storage plant. While this technology is not unheard of in Connecticut, it is not a technology that has been commonly used there, as it has generally incurred a greater first cost than a traditional central plant. JP Engineering, having designed several partial ice thermal storage plants at other locations, was confident that a design incorporating partial ice thermal storage into the total system could be constructed without a significant increase in initial cost.

As the construction was partially funded through the rental structure between Carpenter Companies and the primary building occupant, both companies were acutely interested in the initial cost of the construction, as well as in the potential energy savings which could result from the use of a partial ice thermal storage system. JP Engineering was asked to provide preliminary designs for both a conventional chiller plant and for a partial ice thermal storage application. These initial designs demonstrated that a partial ice thermal storage plant, if incorporated into the complete system design, could be constructed with no incremental difference in first cost over a conventional central plant system design.

With the potential energy savings associated with a partial ice thermal storage plant, and no incremental first cost increase, the thermal storage application was an easy choice. The next major decision facing the design and construction community for this $2.2 M project was selecting a controls vendor and manufacturer willing and able to work within the constraints of the project and capable of making JP Engineering’s innovative design concepts work.

JP Engineering needed a control system capable of interoperability with multiple vendors and which would provide real-time ready access to the information it was collecting and using. Said Joseph D’Amico of JP Engineering, “It was an interesting design and control concept. We knew we were pushing the envelope a little bit. In doing so, we limited the field in terms of equipment, manufacturers, and representatives…Internet capability was key in our decision. Until you can connect people through the Internet, you can’t achieve or realize the true value of a system.”

JP Engineering and Carpenter Companies considered bids from several competitors, but selected Automated Logic’s native BACnet WebCTRL system based on its built-in interoperability and intuitive web-based user interface, as well as its flexibility in terms of scheduling, adjusting setpoints, and problem notification, which met the tenant’s requirements for the selected control system. They were also very impressed with the commitment from Automated Logic Corporation’s corporate office to support the product and with the reputation of RCMS Controls, ALC’s local representative.

Bob Marra, Vice-President of RCMS Controls, said “RCMS specializes in retrofits and seamless controls system conversion while buildings are occupied. We have a strategy for conversion and back-up plans to handle contingencies.” Apparently the strategies worked, as the controls system conversion was accomplished with the building fully occupied, with the indoor environment maintained, and without complaints from building occupants related to the conversion.

RCMS was able to work within the time constraints related to the other facets of the retrofit and in the windows of opportunity defined by other trades without delaying any move-in-dates defined by the phases of construction. Ed Rousseau of Carpenter Companies stated, “I give RCMS a lot of credit. They were working with an application new to them [partial ice thermal storage], plus a new control technology, and a tight schedule. Bob and his guys really pulled it together.” D’Amico agreed, commenting that “ALC and RCMS have surpassed their commitment and our expectations.”

Energy savings were anticipated from the partial ice thermal storage plant, which uses the chiller plant to make ice from 11pm to 7am, when electric rates are lower, and then uses that ice to supplement chiller operation during peak hours from 7am to 11pm. Connecticut Light and Power offered an incentive based on the anticipated energy savings from the chilled water plant pump VFDs and AHU fan VFDs. In addition, the controls strategy used at the site utilizes free economizer purge and pre-cooling of the building when weather allows. Other energy conservation strategies include optimal start and night setback setpoints on the zones throughout the building.

So far, the energy savings on the building have exceeded expectations. Electrical savings have exceeded $7K/month during the summer months, and are expected to increase during the shoulder season and the winter, as the building experiences a year-round cooling load, and the building is now equipped with economizer cooling. This is especially exciting because these savings have been realized despite occupancy added during the course of the retrofit and include exterior lighting and elevator loads previously billed separately from the building.

In addition, the building occupants now enjoy at least the full ventilation required by ASHRAE at all times. CO2 demand strategies are used to increase ventilation over that minimum if necessary, and the night pre-cooling algorithm often completely purges the building with outside air before occupants arrive. As the building occupant’s facility manager observed, “In an office that employs close to 1000 employees, the task of maintaining consistent comfort levels throughout large open spaces is always a challenge. The old system could not meet those challenges because of its limitations and need for costly maintenance. We are just beginning to see the true value of the ice storage system and its potential capabilities for which it was designed.”

Due to the extraordinary teamwork within the design and construction community, and the excellent selection of equipment and controls, all of the project objectives for this challenging retrofit were achieved. When asked if any unexpected benefits were realized during this project, Ed Rousseau replied, “No – but I expected a lot.” George Carpenter of Carpenter Companies added “RCMS and ALC did an excellent job for us. They stuck with us no matter what came up. They addressed all issues, and we are very happy with the system.” Because of this project’s technical accomplishments, a historic part of the Bristol landscape has been preserved and converted to a state-of-the-art environment for the future.