1

Lamp operating factor

Published lumen output is based on laboratory conditions Voltage

Rated at line voltage of 115V Standard reactor ballast

Electromagnetic (ballast factor =< 1) Electronic (ballast factor =<> 1)

Vertical lamp burning position for high intensity discharge lamps

2

Luminous efficacy is the light output per unit of electrical power [W] input, or lumen/Watt [lpw].Theoretically 1 W 683 lm monochromic green light 1 W 200 lm white light

Realistically incandescent lamps: 10 to 25 lpw efficacy Fluorescent lamps: 50 to 95 lpw

Interior spaces in large office buildings Heat from lights, appliances, people need year-round cooling

3

Energy distribution of typical 40W cool white fluorescent lamp [Figure 15-8 in Tao & Janis 2001]

4

Fluorescent lamps have negative electrical resistance. Once arc is struck, ionized mercury vapor becomes increasingly more conductive

A ballast is therefore used to (1) boost the voltage at the lamp terminals to start and (2) limit the maximum flow of current.

Ballast factor [-] is the ratio of the light output [lm] produced by lamps operating on a commercial ballast to the light output [lm] of the same lamp operating on a standard reference ballast in the laboratory. Values range from 0.8 to 1.2

5

Q = 1.1 * CFM * (Tspace - T supply)and assume Tsupply air = 55°F

Ex. 2-2 Cooling Space heat gain

= 69,551 Btu/hr

CFM supply =

69,551 Btu/hr(1.1 * [78°F-55°F])

= 2,750 cfm

Ex. 2-3 Cooling + PlenumSpace heat gain

= 43,684 Btu/hr

CFM supply =

43,684 Btu/hr(1.1 * [78°F-55°F])

= 1,727 cfm

6

HVAC Delivery Systems

Produce heating & cooling – head-end devices Furnaces and boilers Refrigeration devices

Move heat transfer fluids Air handling equipment Ducts, grilles, and diffusers Pipe and pumps

Control delivery Ability to maintain space conditions Complexity of operations and maintenance Energy consumption

7

Methods of Control

1. Vary T of supply air + hold flow = cte

2. Vary flow of warm and cold air + hold T = cte

3. Vary T and vary flow of supply air

ZONE is an area for which temperature (humidity) is controlled by a single thermostat.

8

Basic Control Devices Sensor: measures the monitored or controlled variable Controller: processes the sensor signal and decides to send signal to monitoring station or to actuator. Two-position or proportional signal Direct- or reverse acting

Actuator: manipulates equipment (e.g., damper or valve) to meet desired point of the controlled variable.

9

Sensors

Thermostat senses and controls temperature may have mode switch for heating

and cooling

Humidistat is a device that senses and responds to humidity, relative or absolute

10

Other sensors

Pressure switches and transmitters Flow switches and transmitters Speed switches and transmitters, which respond to flow, pressure, or a program Position switches, which respond to signals to open, close, and modulate dampers, valves, etc.

11

Life Safety System

Sandwich system Negative pressure on fire floor Positive pressure on floors immediately

above and below allow occupants to evacuate the fire floor minimize opportunity for smoke to migrate

to surrounding floors

Smoke exhaust fan Stair pressurization fan Equipment shutdown

12

San Francisco Civic Center

Project organization Floor by floor system = sandwich construction (drawing Ozger)

Placement of air terminals, VAV system Hierarchical control system

13

Passive cooling design strategiesby climate [Fig. 2.13 in Stein and Reynolds]

14

Dual control system -- GAP

Mixed air (see paper)