Environmental Controls I/IG Lecture 14 Mechanical System Space Requirements Mechanical System Exchange Loops HVAC Systems Lecture 14 Mechanical System Space Requirements Mechanical System Exchange Loops HVAC Systems

Mechanical Room Sizing Mechanical Room Sizing

Mechanical Room Contains primary equipment (boiler, chiller, etc.) Usually adjacent to other service areas (loading docks, electrical substation, transformer vault, etc.) Generally away from public entry Include space for service/maintenance S: p. 398, F.10.18

Mechanical Room Sizing Generally sized based on total floor area in building served S: p.391, T.10.3

Mechanical Room Sizing Size mechanical room space Application Square Footage S: p.391, T.10.3

Mechanical Room Sizing Sizing Example 150,000 SF Department Store Mechanical Room: 3,200 sf S: p. 391, T.10.3

Fan Room Sizing Fan Room Sizing

Fan Rooms Contain secondary equipment (air handlers, heat exchanger, etc.) Usually adjacent to or within area served Include space for service/maintenance S: p. 418, F.10.42

Fan Rooms Require connection/ access to fresh air Require means of discharging return air/ exhaust air Minimum 25’ distance of fresh air inlet away from contaminant source University of Michigan Hospital, Ann Arbor, MI

Fan Room Sizing Generally sized based on total floor area of the thermal zone in building served S: p. 392, T.10.4

Fan Room Sizing Size fan room Application Square Footage S: p. 392, T.10.4

Fan Room Sizing Sizing Example 150,000 SF Department Store Fan Room: 5,200 sf Fresh Air Inlet: 550 sf Exhaust Air Outlet: 450 sf S: p. 392, T.10.4

Fresh Air Inlets Avoid contamination sources (25’ minimum) Loading docks Smoking areas Cooling Towers Exhaust air outlets Plumbing vents Others…

Mechanical System Exchange Loops Mechanical System Exchange Loops

Mechanical System Exchange Loops Heat is removed/ added via heat exchange loops. S: p. 394, F.10.15

Mechanical System Exchange Loops Cooling Mode S: p. 394, F.10.15

Mechanical System Exchange Loops Heating Mode S: p. 394, F.10.15

Cooling Tower Cooling Tower

Cooling Tower Divided into a series of cells for redundancy/ serviceability Significant structural load: Rooftop vs At-grade Potential air contamination Locate based on prevailing wind direction S: p.407, F

Cooling Tower Service access needed for water treatment/debris removal Biocides can cause etching on glass and other surfaces Minimum 25’ distance away fresh air inlet or fenestration University of Michigan Hospital, Ann Arbor, MI

Cooling Tower Sizing Sizing Example 150,000 SF Department Store Cooling Tower: 560 sf S: p.391, T.10.3

HVAC Systems HVAC Systems

System Types All-Air Air-Water All-Water Unitary Refrigerant System

Selection Criteria Control capability and flexibility required Environmental requirements Cost of construction Energy consumption System effficiency

All-Air Systems Heating/cooling media delivered via air only Advantages: Humidification & Heat recovery Complex zoning Close humidity & temperature control (exc. VAV) Can use outside air for economizer cycle Disadvantages: Special care for maintenance access Supplemental perimeter radiation may be needed Higher volume of space needed

All-Air Systems Single zone Terminal reheat Multizone Dual duct Variable air volume (VAV)

Single Zone One thermostat controls several rooms in a single thermal zone Applications requiring air filtration and humidity control Uneven comfort for multiple rooms

Terminal Reheat One thermostat controls one room as a single thermal zone with a reheat coil control discharge air temperature Poor energy efficiency

Multizone One thermostat controls discharge dampers to adjust air temperature to each room Small buildings with limited distances for duct runs Simultaneous heating and cooling

Dual Duct One thermostat controls mixing box for each room Applications requiring precise control of temperature and humidity Energy inefficient High maintenance Expensive to build

Variable Air Volume One thermostat controls VAV valve for each room and reduces airflow under lower load Applications where loads vary significantly (offices, schools) Poor humidity control Subcooling

Distribution Paths Air may be distributed from the ceiling or the floor

Distribution Paths—Ceiling Conventional distribution is from the ceiling Air discharge: 55ºF Velocity is fpm S: p.431 F.10.54

Distribution Paths—Floor Also known as displacement cooling Air discharge: 60+ºF Velocity is slower than ceiling discharge Higher ceilings S: p. 387, F S: p. 425, F.10.48

Air-Water Systems Heating/cooling media delivered via air and water Advantages: Flexible placement Centralized humidity and filtration Space heating Disadvantages: Condensation Noise Induction Fan Coil Unit S: p. 388, F.10.13

All-Water Systems Heating/cooling media delivered via water only Advantages: Flexible placement Space heating Disadvantages: Condensation Noise

Fan Coil Unit Fan draws air from room across coils Flexible Less space Low cost Noise Poor ventilation/humidity Maintenance Condensation control Simultaneous heating and cooling S: p. 390, F.10.14

Unitary Refrigerant System Heating/cooling media delivered via local equipment Advantages: Individual room control Independent heating and cooling Single zone affected by malfunction Low initial cost Reliability Disadvantages: Short life Noise Humidity control Air filtration Ventilation Through the wall air-conditioning Heat pumps