hvac basics -a
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HVAC SYSTEMS
Heating, Ventilation and AirConditioning
Provides comfort for people
Allows humans to exist under adverse conditions.
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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
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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
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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
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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
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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
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Thermal Factors
affecting Metabolic HeatTransferPg. 9-9Combining evaporation, radiation
and convection……..
Dry Bulb Air Temperature
Humidity
MRT
Air Velocity
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Comfort RangesPg 9-11
• Comfort,
Productivity & Energy
Conversation
• Comfortconclusions:
RH=30% & 60%
Temp
Air velocity
No short c clin
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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
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Building Heat Loads-
External
•Solar…
•Ventilation and Infiltration…
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HVAC DesignConcepts -Zoning Fig. 9-5, Pg.9-15 Zoning: Division of building systems into
independent temperature control
Zone: Distinct area conditioned air serves
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Basic Refrigeration Cycle
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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
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Packaged Rooftop Units (RTU)
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Split System
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(VAV) Variable Air Volume
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VAV Terminal Units
Variable volume:Parallel
Constant volume:Series
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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
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Hydronic systems
Water cooled Chiller
Air Cooled Chiller
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Hydronic System Major Equipment
Chillers
Boilers
Cooling Towers
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Chilled Water System
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Economizers
Air Side Water Side
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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
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Enthalpy Wheels
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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
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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
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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
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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
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Additional Equipment
Heat Exchangers
Humidifiers
Silencers
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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.
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Acoustics
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Octave Band
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