0 Overview of Hvac Systems Jk Means

8/3/2019 0 Overview of Hvac Systems Jk Means

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INTRODUCTION

TO HVAC SYSTEMDESIGN FOR

ARCHITECTS

Presented initially on Feb. 11-12, 2004 and annually thereafter in Lear

Auditorium at Lawrence Technological University, Southfield, Michigan

Prepared by Prof Janice K. Means, PE, LEED AP


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So what is behind those

walls, above our headsand below our feet that

has so much to do with

making us comfortable

in buildings?


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and what do

architects need toknow about these

heating, ventilatingand air-conditioning

(HVAC) systems?


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Buildings consume 50%of the worlds energy.

--quote from Keynote Address given by Susan S. Szenasy(Editor In Chief of Metropolis) at the ACSA/AIA Teachers

Seminar at Cranbrook Academy of Art in Bloomfield Hills, MI

in June, 2003

*Note that some experts cite lower percentages for the

portion of energy used by buildings in the United States.


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According to the DOE , buildings in

the U.S. use varying percentages of

their total energy use to provide

comfort heating and cooling for

occupants.

56% in private homes 38% in multi-family residences

52% in schools (K-12) 37% in universities

41% in government buildings 34% in offices

40% in retail structures 28% in health care structures

22% in hotels motels


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There are about 5

million commercialbuildings in the

United States.

--www.sustainableenergy.org


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Office

Equipment

16%

Hot Water

9%

Ventilation

5%

Space

Cooling

9%

Space

Heating25%

Lighting

29%

Misc.

7%

Office BuildingEnergy Use

www.eere.energy.gov/buildings/index.cfm?flash=yes


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What is the architects rolein creating a comfortable

environment for occupantswhile effecting responsible

energy use?

Isnt up to the mechanicalengineer?


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Even a superior HVAC systemcannot compensate for a poorly

designed building

one where not enough

mechanical space has beenprovided

or which is an energy hog.


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So now lets talk aboutwhat you need to know

about HVAC equipmentand its design.


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Major SystemComponents in HVAC

Systems

Energy ConversionEquipment

Distribution Equipment

Control Equipment


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Energy Conversion Equipment:

converts fuel to heat (or cool)

Examples: chilled watercondensers, chillers, boilers,

furnaces, domestic hot waterheaters, etc.

Major System Components in HVAC Systems


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Distribution Equipment:

transports fluid holding heat(or cool) to/away from

conditioned space

Examples: ducts & plenums

with fans or pipes with pumps



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Control Equipment

Sensors to measure temperature,

humidity, purity levels, etc.

Senders to relay measured/sensed

information to/from controller device Software w/ hardwareto monitor

and change conditions

Examples: thermostats & humiditysensors; wires & pneumatic hoses;

controllers, BAS, EMS, etc.



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Major HVAC Systems

1. All Air

2. Air & Water

3. All Water

4. Unitary

5. RadiantPanels

H/C Equipment

Centrally Located

w/

Air-Handling

Central or By Floor

H/C Equipment

Adjacent to Zone


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All Air Cooling is always done from a central air

stream

Heating is done from the central air

stream, & sometimes at azone (reheat)

Hot water loops from boilers to heating

coils in air stream &, sometimes at zone

Cold water loops from chillers or

condensers to cool coils in the air stream

Air is provided atConstant Volume (vari-

able temperature) orVariable Air Volume

(constant temperature)

Major HVAC Systems


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All AirMajor types of ALL AIR systems

(many variations)

Single Zone

Terminal Reheat* Single Duct VAV

Dual Duct

Multi-zone

*Shown combined with a Single Duct VAV

in following diagrams.

Major HVAC Systems


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All Air SystemsMajor HVAC Systems

Re-heat coil

Pre-heat coil

Filter(s)

Cooling coil

Fan

Every ALL AIR system has these components, however,those in redmay be arranged differently.

E.A.(exhaust air)or relief air to

outdoors

O.A. outsideair through

louvers

R.A.

One or more

ducts provide

S.A.

(supply air) toconditioned

space

R.A. (return air)

from conditioned space

Air Handling Unit


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All Air Systems

Major HVAC Systems

Boiler

Chiller

Fan

Re-heat coil

R.A.

Pre-heat coil

Filter

RA

O.A.

E.A.

SACooling coil T

Single Zone System

CV (typically)


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Major HVAC Systems

All Air Systems

Single Duct Variable Air Volume

with variations

Pre-heat coil

Boiler

Chiller

Fan

Re-heat coil

R.A.

Filter

RA RA

O.A.

E.A.

o o o o o

o o o o o

VAV Boxes

(optional fan for fan-powered VAV &

optional Reheat coilfor Terminal Reheat)

SA SA

Cooling coil

TT

VAV


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Major HVAC Systems

All Air Systems

Chiller

Fan

Heating coilsPre-heat coil

Filter

E.A.

Cooling coils

Mixingbox

Boiler

O.A.T

CV shown (or VAV)

Dual Duct Air System


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Major HVAC Systems

Multi-Zone System

Boiler

Chiller

Fan

Heating coils

Pre-heat coil

Filter

O.A.

E.A.

Cooling coils

Mixing controls

T

T

T

All Air Systems

CV shown (or VAV)


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ALL WATER systems will be

discussed prior to

AIR & WATER systems.

Major HVAC Systems


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All Water

Major types of ALL WATER systems

Two Pipe

Four Pipe

Major HVAC Systems


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All Water

Able to only heat and cool

Cannot provide humidification

Air quality provided by

windows, separate system, or

through unit ventilators

Water is delivered from centralequipment, e.g., boiler or chiller

Major HVAC Systems


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All WaterMajor HVAC Systems

Refrigeration

Machine

Boiler pumps

Fan Coil Unit Shown

(can be convector or unit ventilator)

Valves* switch seasonally betwee

boiler and refrigeration machine

for ONLY COOLING or

ONLY HEATING at one time2-Pipe System

T T T

* Actual connections not shown.


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All WaterMajor HVAC Systems

Refrigeration

Machine

Boiler pump

T

4-way valveFan Coil Unit

COOLINGHEATING

4-Pipe System

T T


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Air & Water

Major types of Air & Water systems

Induction

Fan Coil with Supplementary Air

Radiant Panels with

Supplementary Air

Major HVAC Systems


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Air & Water

Most heating and cooling is

provided by the water (hydronic)

system

The air portion of the combined

system need not be as large as for an

all air system because it is justsupplying ventilation air (and

sometime humidification)

Major HVAC Systems


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Air & WaterMajor HVAC Systems

Induction System

T

Room air is

induced intoterminal unit

Chiller

Pre-heat coil

Filter

Boiler

100%

O.A.

Fan

Re-heat coilCooling coil

TerminalRoom Unit


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Chiller

Pre-heat coil

Filter

Boiler

100%O.A.

Fan

Re-heat coilCooling coil

TerminalRoom Unit

Fan in Terminal

Unit pulls air in fromroom and assists

central fan

Fan Coil with Supplementary Air

T


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Radiant Panel with Supplementary Air

Chiller

Pre-heat coil

Filter

Boiler

O.A.Fan

Re-heat coil

Cooling coil

Wall or Ceiling

Mounted RadiantPanel

E.A.T


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Major HVAC Systems

Unitary SystemsMajor types of Unitary systems

Packaged Units roof or groundmounted factory assembled

Split SystemsAir coil condenser outside

& AHU in ceiling, e.g., residential air-conditioning

PTAC (Packaged Terminal ConditioningUnits), e.g., window air-conditioner

(Only packaged units will be discussed in this

presentation.)


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Packaged Units Packaged units contains:

fans, coils and filters (AHU-function)

refrigerant compressor & condenser

controls

Energy

conversion &distribution

equipment are

housed in the

same package

Ducts are run directly from the units to the area to

be conditioned. Typically, separate units serve each

zone.

Major HVAC Systems Unitary Systems


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Radiant PanelsMajor types of Unitary systems

Air-heated or air-cooled panels suppliedby air heated/cooled indirectly by a boiler,

chiller or refrigerant compressor.

Hydronic (water-heated) panels

containing embedded or mounted pipes or

tubes which can be mounted.

Electric (resistance-heated wires) panels

Major HVAC Systems


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Often installed with central systems

(as discussed in the Air & Water system

section)

Also available in packaged panels

ready to mount or hang, and powered bynatural gas or electricity

Electric panels are sometimes used forspot heating in residential

(This presentation will not elaborate further on radiant panels.)

Major HVAC Systems Radiant Panels


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Systems Most Commonly Usedin Commercial Structures

All Air

Air & Water

Unitary Packaged Units


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Central Systems

require 1 or moreequipment room(s) in

basement, penthouse or

roof & fan rooms in 1 or

more areas

have extensive

distribution systems

require complex

controls

Systems Most Commonly Used in Commercial Structures

Packaged Systems

have equipmentdistributed throughout

building (or overhead

on roof of low-rise

structures)

require minimal

distribution systems

need only simplified

controls

Comparisons of Central & Local Systems

S C l d C l S


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Comparisons of Advantages of Central& Local Systems

Central System Advantages

easier to control/maintain IAQ

more flexibility in locating

ventilation intake locations

waste heat energy can more

easily be recovered & used by

another process

equipment easier to maintain w/o

interrupting occupants

noise & waste heat easier to

control

Local System Advantages

doesnt require majormechanical areas w/in building

more energy efficient in

responding to scheduling &

diversity variations

system breakdowns do not take

down entire building

simple operating controls

S M C l U d i C i l S


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Comparisons of Central & Local Systems

Central System Disadvantages

entire building affected

if major piece of

equipment goes down

requires space for

large distribution

systems

energy may be wasted

if entire building or

major zone must be

conditioned for a smallarea

easier to provide

smoke control if fire

Local System Disadvantages

noise is harder to control

since equipment is locatedcloser, or within, occupied

spaces

more difficult to harvest waste

heat maintenance is demanding &

may disrupt occupants

poorer IAQ since numerous

filters must be maintained

use in interior zones prevents

needed access to outdoor air

more difficult to control smoke

during fire


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Summary

Hopefully, some of the mystery behindHVAC systems and implications for

design to optimize HVAC effectiveness

has been gleaned from this

presentation. Sources for additional

information and direction follow.

###


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Studio Companion, by Edward Allen, 1989,by John

Wiley & Sons

www.ashrae.org: home for the American Societyof Heating, Refrigerating and Air-Conditioning

Engineers, a standards-writing professional

society for HVAC and Refrigeration.

www.usgbc.org: home of the United States

Green Building Council (LTU is a new member),

group promoting sustainable architecture anddevelopers of the sustainability standard, LEED,

Leadership in Energy & Environmental Design.

For More Information


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Prof. Janice K. Means, PE, LEED APCollege of Architecture and Design

Lawrence Technological University,

Southfield, Michigan 48075Office A-217 248.204.2852

For More Information,contact

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0 Overview of Hvac Systems Jk Means