hvac basics -a

8/12/2019 HVAC Basics -A

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HVAC SYSTEMS

Heating, Ventilation and AirConditioning

Provides comfort for people

Allows humans to exist under adverse conditions.



Key Concepts

80% human energy = heat lost;Thermal comfort is the equal bala

nce of

HEAT:

Sensible (temp.) and Latent (state) heat =cooling loads - Systems design integration

Internal and External Heat LoadsSystems design

IAQ



Chapter Thoughts…….

Units -- miles, miles/hour, gallons,gallons/minute, KWH ……BTU’s, oF,%Relative Humidity

Are you comfortable?

Roles &Responsibilities?….Home…Work/work

assignment

Heat What do we know about it?

...can not be destroyed…moves from one place toanother and converted



Heat, pg.9-5, 4

- 1 lb. melted = 144 BTU’s

absorbed producing a

cooling effect

- 1 ton = 2,000 X or 288,000 BTU’s

- “Rate” = 12,000 BTU’s/hour

over 24 hours

Tons of Refrigeration - larger unit ofheat flow:

Relative Humidity, % of saturationpossible

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Heat

1 lb. ICE

1 lb. WATER

WATER VAPOR

Dewpoint

Temperatur

e The temperature at which air isfully saturated with moisture andcondensation starts



Heat, pg 9-5&6

U

Heat Flow

In/Out…. Heat

Conductivit

y- Value

Btu/hr-ft2-oF

Coefficient of TransmissionWalls, Roofs, Windows

oF1

oF2

feet

feetMaterial R-value

Resistance to heat flow -

insulation

Btu’s per hour



Comfort conditioning of interior spacesall year - heat removed and added

ASHRAE - treating air to controlsimultaneously:

Temperature

Humidity (moisture)

Cleanliness (filtration)

Distribution (ventilation, air changes)

Noise

Air Conditioning(Primary responsibilities of HVAC

systems), pg9-6



Thermal Factors

affecting Metabolic HeatTransferPg. 9-9Combining evaporation, radiation

and convection……..

Dry Bulb Air Temperature

Humidity

MRT

Air Velocity



Comfort RangesPg 9-11

• Comfort,

Productivity & Energy

Conversation

• Comfortconclusions:

RH=30% & 60%

Temp

Air velocity

No short c clin



Building Heat Loads-

Internal

Four main categories:

People, Fig. 9-6, pg. 9-17*Lighting, Fig. 9-7& 8, pg. 9-

18*

Equipment

System, HVAC gains/losses



Building Heat Loads-

External

•Solar…

•Ventilation and Infiltration…



HVAC DesignConcepts -Zoning Fig. 9-5, Pg.9-15 Zoning: Division of building systems into

independent temperature control

Zone: Distinct area conditioned air serves



Basic Refrigeration Cycle



System Types

Packaged Rooftop Unit

Indvidual Split System

Hydronic -Air Cooled

Hydronic -Water Cooled

Geothermal

VAV Variable Air Volume

Under Floor Air Distribution (UFAD)

VRV System



Packaged Rooftop Units (RTU)



Split System



(VAV) Variable Air Volume



VAV Terminal Units

Variable volume:Parallel

Constant volume:Series



Under Floor Air Distribution (UFAD)

Advantages Individual Controllability

Re-Configurability

2 Extra LEED Points

Disadvantages More Expensive ($8/SFfor raised floor)

Flexible for Change

Inland Power &Light First UFAD in area



Hydronic systems

Water cooled Chiller

Air Cooled Chiller



Hydronic System Major Equipment

Chillers

Boilers

Cooling Towers



Chilled Water System



Economizers

Air Side Water Side



EconomizersFree cooling source: When available, use cool

outdoor air instead of mechanically cooled air.

55o

F

80 oF

Minimum supplyof outside air

Normal Operation

Outside air dampers arepositioned to provide theminimum outside air

Economizer Operation

Outside air dampers are fullyopen. Maximum outside air isprovided

80 oF

55 oF andup

85%outsideair

85%exhaust

HVAC-27



Enthalpy Wheels



Air Distribution

Grilles, Registers Many options

GU Russell TheatreReturn Grille

Return Plenum Extra cost for plenum

rated cable is less thancost of return ductwork

No Combustables



Outside Air Louvers

Outside Air Louversprovide an opening in abuilding wall to push airout, or pull air in.

Provide clean outdoor air,avoid: loading docks

exhaust vents

plumbing stacks

waste collection

stagnant water



Metal Ducts

Square Ductwork Most common

Low height

Round Ductwork Less Expensive

Easy to Install

Lower static pressure

Taller than Rectangular

Higher pressure

Less Sound

Oval Ductwork

Same advantages of round Height similar to rectangular

More expensive than rectangular



Fabric Ducts

Great for certainapplications Gyms

Pools Manufacturing

Spokane ScienceMuseum

Advantages

Great Diffusion Easily Cleaned

Fun

Same cost asmetal

Saved $300,000 incost at high

school. Loweredchilled water temp,& air temperatures



Additional Equipment

Heat Exchangers

Humidifiers

Silencers



Kitchen Hoods

Type 1: Hoods designed for grease exhaustapplications

Type 2: Hoods designed for heat and steamremoval and other non grease applications. (NFPA

96 does not cover)Where are Type 1 Commercial Hoods Required? NFPA 96 “Cooking equipment used in processes

producing smoke and grease-laden vapors shall beequipped with…”

NPFA 96-A-1-1 “…intended to include residential

cooking equipment where used for purposes otherthan residential family use”

Type 1 Hood Clearances

18 inches to combustible material

3 inches to limited-combustible material

0 inches to noncombustible material

A restaurant with a commercial gas range isrepresented by the resteaurant owner to beused ony for the preparation of soups. What

type hood is required?Type 1 hood is for collection and removal ofgrease laden vapors,and smoke. Type IIhood is for removal of steam, odors, andvapors. It would be hard pressed to find arestaurant that only produces soups, withthat commercial range. Hoods: whererequired, installed at or above all commercial-type deep fat fryers, broilers, fry grills, steam- jacketed kettles, hot-top ranges, ovens,barbeques, rotisseries, dishwashingmachines, and similar equipment thatproduces comparable amounts of steam,smoke, grease, or heat in a food processingestablishment. Food processing

establishment shall include any building orportion used for the processing of food. Soupis a liquid food made up of simmeringvegetables, seasonings, and often meat orfish. It is the potential of the equipment(Commercial gas range), rather than theutilization, that must be evaluated. So, whattype of hood would be required for thatcommercial gas range in a restaurant wouldhonestly be open for discussion. You willprobably have some input from your localFire Dept. through plan check as with theCounty Health dept. Requirements. I know ofone City close to us that when a pizza parloropens, no matter what, they require a type 1

hood. Depending on the type of pizza oven,we have allowed a type II.



Acoustics



Octave Band



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