Microsoft PowerPoint - HVAC FINAL.ppt[1]

7/27/2019 Microsoft PowerPoint - HVAC FINAL.ppt[1]

1/20

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


2/20

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%


3/20

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


4/20

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%


5/20

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%


6/20

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:


7/20

Types of EquipmentHeating and Cooling

Air source heat pumps

Geothermal heat pumps

Types of EquipmentHeating and Cooling


8/20

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%


9/20

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


10/20


11/20

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


12/20

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


13/20

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


14/20

Ductwork Sealing

Mastic must be installed on seams &

jo ints of ductwork, not the insulation!

Sealing at the HVAC Unit


15/20

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


16/20

Combustion Safety

Furnace, Water Heater

The Purpose of Venti lation

Fresh air foroccupants

Dilute pollutants


17/20

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


18/20

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


19/20

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


20/20

Outside airdamper at airhandler tomodulate flow

Exhaust fansremovepollutants fromtheir source

Lessapplicable for

cold climates

Outside air and spot venti lation

Documents

Microsoft PowerPoint - HVAC FINAL.ppt[1]