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7/27/2019 Microsoft PowerPoint - HVAC FINAL.ppt[1]
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MechanicalSystems
Heating, Cooling, and Ventilation
Objectives
Learn the importance of system designon energy efficient performance
Be familiar with equipment options
Learn basic design and installationguidelines to ensure energy efficientperformance
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When to Upgrade Mechanical Systems
Close to end of
useful life
High utility bills
Need frequentmaintenance
Excessive noise
Occupantdiscomfort(e.g., rooms too hot or cold, stuffiness,excessive humidity or dust)
Existing Heating Equipment
Example: TO REPLACE OR
NOT TO REPLACE?
Annual heating bill $734
AFUEexisting 78%
AFUEnew 96%
Savings = ((0.96-0.78)/0.96) x $734
Annual Savings = $137
Cost to Replace = $2000
Payback ~ 14.5 years; ROI 6.8%
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Importance of Design
Undersized systems= discomfort
Oversized systems= wear & tear onequipment, discomfort(cooling), unnecessaryexpense, higher initial cost
Duct design can affect effic iencyand systems ability to heat/coolevenly
How to Obtain Good System
Design and Installation
Do it yourself
~or~
Find a contractor that will take the timeto design and install it right
Create specifications for contractors
Ensure specifications are followed
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Heating Load
Heat loss occurs mainly by surface heatloss and air leakage
Heat loss is offset by solar gains andinternal heat sources (e.g., people,cooking, computers, lights)
Use high R-value to reduceconduction losses
Minimize infiltration lossesby good air sealing
Internal heat sources help
during the winter
Heating Load
Ceilings15%
Windows19% Doors
3%
Infiltration39%
Floors9%
Walls15%
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Cooling Load Occurs by surface heat gain, air
leakage, solar heat gain, and internal
loads (heat and moisture).
A function of temperature andhumidity.
+ +
Cooling Load Breakdown
SensibleInfiltration 4%
Ceilings21%
Walls12%
Windows23%
Doors
2%
InternalHumidity
13%
InfiltrationHumidity
24%
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Manual J Software
Types of EquipmentHeating Only
Increa
sing
efficien
cy
Increa
sing
eff
iciency
Direct Vent / Sealed
combustion
Power vented
Natural draftIncreasin
g
Increasin
g
safety
safety
Furnaces and Boi lers:
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Types of EquipmentHeating and Cooling
Air source heat pumps
Geothermal heat pumps
Types of EquipmentHeating and Cooling
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Types of EquipmentCombined Systems
Combined space and water heating
Furnace/Boiler Efficiency
Efficiency measured by AFUE
Condensing units can haveAFUE rating as high as 96%
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Heat Pump EfficiencyHeating Mode Measured by HSPF or COP
ENERGY STAR at HSPF of 8
Cooling Mode
Cooling efficiency measuredby SEER
Federal minimum SEER 13
ENERGY STAR cri terion SEER 14
Cooling Equipment
Efficiency Measured in SEER
Federal minimum SEER 13
For every 1 SEER increase over SEER13, ~8% higher efficiency
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When possible, locate ductwork within
the conditioned space
Ductwork Location
Increase comfor t
Reduce utility bills
Potentially lowerconstruction costs
How to locate ductwork within
condit ioned space
Ductwork Location
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Ductwork Design Details Dampers at takeoffs
Metal elbows for tight turns
Gradual turns with flex ducts(radius of turn must be > than
the duct diameter)
Ductwork Design Details
Ducts should not
originate from theend of or within 6
of the end of trunk-
line or plenum cap
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Ductwork Design Details
Dont use stud or joistcavities as ducts
Use ducts designed to fitinside those spaces
Ductwork Sealing
Al l duct connections mustbe sealed with mastic,including connections to:
Plenums
Y-joints
Boots
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Ductwork Sealing
Mastic must be installed on seams &
jo ints of ductwork, not the insulation!
Sealing at the HVAC Unit
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Testing & Verification
Duct Blaster
Flow Hood
Sealed building envelope
Controlled mechanical ventilation
Sealed combustion equipment or CAZ test
Duct Blaster test
Indoor Air Quality
Ventilation Filtration Duct Blaster
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Combustion Safety
Furnace, Water Heater
The Purpose of Venti lation
Fresh air foroccupants
Dilute pollutants
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Keys to Indoor Air Quality
Eliminate (remove pollutant source)
Separate (seal or contain pollutants)
Ventilate (dilute pollutants)
Filter (clean and remove pollutants)
Negative / Exhaust
Strategies
Quality fans can runcontinuously
Preferred forcolder climates
Doesnt typically offercontrol of where inletair comes from
Not recommended for
humid climates Spot ventilation is anexcellent strategy forall climates
Source:
JLC
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Exhaust Fan Ventilation
Bath and kitchen fansvent to the outside, rigidduct is preferred
Balanced Ventilation
Controlledinlet andoutlet withfiltering
Could beseparatefans orsingle unit
Opportunitiesfor heatrecovery
Centralexhaust fan
Damperedoutside air ductCentral heating andcooling system
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Air to Air Heat Exchanger Opportunities
for energy
recovery
HRV recovers heat
ERV transfers
heat &
moisture
Positive Pressure Venti lation
Tends to drive pollutants out
Ai r enters f rom known sourceplus filtering and mixing
Could be separate fan orduct connected to return
Ai rCycler canrun A/H on regular
basis Reduces chances
of backdrafting
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Outside airdamper at airhandler tomodulate flow
Exhaust fansremovepollutants fromtheir source
Lessapplicable for
cold climates
Outside air and spot venti lation
Recommended