ASHRAE Journal - March 2009 - (Page 23)

Exhaust 15,000 cfm VF VE-1 RC-1A Recup.: 152kW Gas Fired Indirect Heating Unit Outside Air Temp: 15°F RC-1 D Mechanical Room 2.5 in.Ø VA-1 S C RC-2B Exhaust Bathrooms & Center Roof X FAU-1 VF 40,000 PCM Recup.: 167 kW RC-2A 2 in.Ø Sup: 55°F 2 in.Ø 50 US gpm 90°F 3 in.Ø PC-2 70 US gpm 2.5 in.Ø Interior Cooling Tower Cooling Tower Turned Off In Winter Sup: 55°F 50 US gpm 132 US gpm 4 – 800 US gpm PC-1 VFD P D X C D Fresh Air 70°F 95°F 8 in.Ø P T° SP:71°F Peripheral Zone Thermostat T° Typical Floor CEP Supply Air Temperature Sensor T° SP:74°F Interior Zone With Override Switch On Main T° Thermostat P Air Conditioning Unit D X C D Sup. 0 – 25% Cold Temperature Sensors Tied Into Controls P S T° T° SP:74°F SP:71°F Peripheral Zone Interior Zone 95°F Typical Floor SP:74°F Interior Zone With Override T° Switch On Main Thermostat Figure 1: This schematic shows the principles of operation for 4200 St. Laurent Ofἀce Tower in Montreal. units are shown in Figure 1 ). The air-conditioning units are independent air handlers with a fan and DX coils, which are cooled by the water from the cooling towers. There are 85 AC units that cool the interior zones during winter. Heating is not required in the building’s interior despite cold outdoor temperatures. The cooling towers are located on the roof (Figure 1). An indirect, gas-fired, fresh-air unit (FAU-1) is located on the roof (Figure 1). FAU-1 supplied fresh air for the building at a volume flow rate of 40,000 cfm (18 878 L/s). The temperature setpoint for the fresh air was originally hardwired to 68°F (20°C) for neutral delivery. The fan of FAU-1 was running six days per week and 12 hours per day at maximum speed. An exhaust fan on the roof evacuated 12,000 cfm (5663 L/s) of air from the building. The exhaust fan (VE-1) is shown in Figure 1 and it is located near FAU-1. VE-1 was running 24 hours per day, seven days per week at maximum speed. VE-1 and FAU-1 are located outside at a distance of about 20 ft (6 m) from each other. Our energy audit proposed a heat recovery system, but conventional systems March 2009 such as a heat pipe or a rotary enthalpy wheel were not feasible because they involved extensive modifications to ductwork. An effective runaround loop would require considerable electrical power and a high content of glycol. The building did not have automated direct digital controls and the heating and air conditioning equipment operated independently. The individual AC units had their own mechanical thermostats. The fin tubes have pneumatic valves with their own thermostats, while the boilers maintained an elevated water temperature. The building’s consumption of natural gas was high and expensive. Between October 2002 and May 2003 (typical timeframe for winter weather in Montreal), before the energysaving measures were installed, the total consumption of natural gas for that winter was 16 million ft3 (451 007 m3), the cost was $182,856 (Canadian), and the winter’s degree days were 8,386°F · days (4659°C · days).1 A normal winter’s degree days in Montreal is 8,235°F · days (4575°C · days).1 A typical year for electrical consumption before any of the electrical energy-saving measures were installed ran from Jan. ASHRAE Journal 23 85°F S T° 85°F 8 in.Ø Air Conditioning Unit Sup. 0 – 25%

Table of Contents Feed for the Digital Edition of ASHRAE Journal - March 2009

Contents Commentary Industry News Letters Meetings and Shows Special Section 2009 ASHRAE Technology Awards Feature Articles Heat Recovery for Office Tower Air Motion Control in the Hospital Operating Room Anniversary Feature: Five Defrost Methods for Commercial Refrigeration Groundwater Issues: Commercial Open Loop Heat Pump Systems Used Filters and Indoor Air Quality Building Sciences Emerging Technologies Washington Report Products Special Products People Classified Advertising Advertising Index

ASHRAE Journal - March 2009

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