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System Layout

Central Plant

The main heating and cooling equipment is located within a 5,000 square foot central plant, on the ground floor of the Coldwell Banker Building at the Round.

Heating: At full build out, water will be heated by four, 7 mmBtu, gas-fired boilers for base load; a 2 mmBtu condensing boiler and two 1 mmBtu condensing boilers for light and peaking loads. Twin, 50 Hp circulating pumps with variable speed drives move the water around the primary hot water loop.

Cooling: At full build out, chilled water will be produced by three variable motor drive chillers. Twin 75 HP chilled water pumps with variable speed drives circulate the water around the primary chilled water loop. Three cooling towers are located on the roof of the South Office Building, supplied by twin 125 Hp condenser pumps with variable speed drives. A heat exchanger allows the use of the cooling towers for direct cooling, rather than operating a chiller, when the weather is cold enough. This practice is often referred to as a water-side economizer.

Electrical: A 250 kW emergency generator provides power in case of a utility outage.

Controls Network: A robust, computer-based controls network (often referred to as a building automation system, or BAS) interconnects the entire heating and cooling system, providing plant optimization and load shaping, and contributing to the plant operating efficiencies. Each element of the controls network is designed to “stand alone” but still communicate with all other parts of the system. If one component were to fail, the rest of the system would continue to operate normally while the failed unit goes to a default setting and alerts the operator. This capability provides maximum interaction an eliminates the inherent vulnerability of a highly centralized control system.

Primary Circulation Loop: The primary loops consist of large diameter, insulated, ductile-iron pipe. Typical pipe sizes are eight inches for hot water supply and return, and ten inches for chilled water supply and return. Main circulation pumps are located within the central plant.

Secondary Circulation Loops: The primary loops connect to the secondary loops within each building’s mechanical room. Secondary circulating pumps with variable speed drives move the water around the in-building chilled and hot water loops, which transfer the heat or cooling to air systems through modulating two-way valves.

Air-Handling Systems: Each building’s air handling systems are the actual end-users of the hot and chilled water. Two types of transfer coils—fan coil units (small) and air handler coils (large)—deliver the heat or cooling to building air systems. Both types of air handlers incorporate variable speed fans that blow air over the water coils to heat or cool the space in response to the controls network.

The retail spaces and condominiums are each served by fan coil units. Generally, one fan coil serves each retail space or condominium. The fan coils provide both heating and cooling to a set point that is easily adjusted by the tenant. The tenant can also adjust the amount of airflow. These inputs from the tenant are incorporated into the operating strategy by the controls network.

The office buildings are all served by large air handler units which serve one or more zones. Zone control is through individually adjustable sensor and control units in every zone served. This ensures effective individually controllable environments throughout the facility. The various inputs from these zones are coordinated by the controls network. The air handlers also have an outside air source (an economizer) that allows the use of outside air for heating or cooling when outside temperatures are appropriate.