Math in HVAC Presented by Mike Veeder HVAC instructor Columbia Greene Questar.
-
Upload
sharlene-moore -
Category
Documents
-
view
213 -
download
0
Transcript of Math in HVAC Presented by Mike Veeder HVAC instructor Columbia Greene Questar.
Math in HVACMath in HVAC
Presented by Mike VeederPresented by Mike Veeder
HVAC instructor HVAC instructor
Columbia Greene QuestarColumbia Greene Questar
Whole House Heat LossWhole House Heat Lossquestion #1question #1
Determine design temp differenceDetermine design temp difference Find total square foot of windows and doorsFind total square foot of windows and doors Find gross wallsFind gross walls Subtract windows and doors from gross Subtract windows and doors from gross
walls to find net wallswalls to find net walls Determine exposed ceiling areaDetermine exposed ceiling area Find floor areaFind floor area
Multiply each by U factorMultiply each by U factor Add all btu’s/degree FahrenheitAdd all btu’s/degree Fahrenheit Multiply by temp differenceMultiply by temp difference Multiply by 15% for duct lossesMultiply by 15% for duct losses Arrive at heating btu loss for houseArrive at heating btu loss for house
Calculate annual heat lossCalculate annual heat lossQuestion #2Question #2
BTU annual = BTUH x HDD x 24hr/day BTU annual = BTUH x HDD x 24hr/day x .75x .75
• BTU annual = 875 x 6860 x 24 x .75BTU annual = 875 x 6860 x 24 x .75
• Annual heat loss is 108,045,000 btusAnnual heat loss is 108,045,000 btus
PropanePropane
• Determine how many gallons of propane Determine how many gallons of propane burned per yearburned per year
• Gal/yr = annual btu / 92,000btu / galGal/yr = annual btu / 92,000btu / gal• Gal/yr = 108,045,000/92,000Gal/yr = 108,045,000/92,000• Gal/yr = 1174 galGal/yr = 1174 gal• Cost/yr = 1174 gal x $2.60/galCost/yr = 1174 gal x $2.60/gal• Cost/yr = $3052.40 x stack loss of furnaceCost/yr = $3052.40 x stack loss of furnace• Cost/yr = $3662.88Cost/yr = $3662.88
ElectricityElectricity
• Determine the amount of electricity used Determine the amount of electricity used on a annual basison a annual basis
• Watt/yr = btu annual / 3.41 btu/wattWatt/yr = btu annual / 3.41 btu/watt
• Watt/yr = 108,045,000/3.41Watt/yr = 108,045,000/3.41
• Watt/yr = 31,684,750 / 1000Watt/yr = 31,684,750 / 1000
• KW/yr =31,684 x .14/kwKW/yr =31,684 x .14/kw
• Yearly cost of electric is $4435.87Yearly cost of electric is $4435.87
Calculate BTU output of a Heat Calculate BTU output of a Heat PumpPumpQuestion 5Question 5
• BTU=1.08 x cfm x delta “T”BTU=1.08 x cfm x delta “T”
• CFM= FPM x .66 x sq. ft of duct areaCFM= FPM x .66 x sq. ft of duct area
Determine cfm of a Determine cfm of a Geothermal Heat pumpGeothermal Heat pumpQuestion #4Question #4
• CFM = fpm x .66 x sq. ftCFM = fpm x .66 x sq. ft
• CFM = 606 fpm x .66 x 2CFM = 606 fpm x .66 x 2
• CFM = 800 cfmCFM = 800 cfm
• Btu = 1.08 x cfm x delta “t”Btu = 1.08 x cfm x delta “t”
• Btu = 1.08x 800 x (92 – 65)Btu = 1.08x 800 x (92 – 65)
• Btu = 23,328 btuBtu = 23,328 btu
Geothermal loop performanceGeothermal loop performanceQuestion #6Question #6
Loop filled with 20% MethanolLoop filled with 20% Methanol
Btu = 485 x gpm x Delta “t”Btu = 485 x gpm x Delta “t”
Btu = 485 x 6 x (40 – 32)Btu = 485 x 6 x (40 – 32)
Btu = 23,280 btuBtu = 23,280 btu
BPI Building Airflow StandardBPI Building Airflow Standard(BAS)(BAS)
Living Space Area = 1500 sq. ft.Living Space Area = 1500 sq. ft.
Basement area = 700 sq. ft.Basement area = 700 sq. ft.
Ceiling height = 8 ft.Ceiling height = 8 ft.
# of Occupants = 4# of Occupants = 4
# of stories above grade = 2# of stories above grade = 2
Location = Albany, NYLocation = Albany, NY
Calculate ventilation required for Calculate ventilation required for buildingbuilding
Airflow(b) = .35 x volume/60Airflow(b) = .35 x volume/60
Volume = 8 x (1500 + 700) = 17,600 Volume = 8 x (1500 + 700) = 17,600 cu. ft.cu. ft.
Airflow(b) = .35 x 17,600 / 60Airflow(b) = .35 x 17,600 / 60
Airflow(b) = 102 cfmAirflow(b) = 102 cfm
Calculate ventilation required for Calculate ventilation required for peoplepeople
Airflow(p) = 15 x # of occupantsAirflow(p) = 15 x # of occupants
Airflow(p) = 15 x 4 = 60 cfmAirflow(p) = 15 x 4 = 60 cfm
Using the higher airflow Using the higher airflow requirementrequirement
Convert cfm to cfm50Convert cfm to cfm50
Minimum cfm50 = airflow x NMinimum cfm50 = airflow x N
N = LBL conversion factor N = LBL conversion factor
Minimium cfm50 = 102 cfm x 15.4 = Minimium cfm50 = 102 cfm x 15.4 = 1570 cfm501570 cfm50
When we read the cfm50 from the When we read the cfm50 from the blower door, 1570 is what is blower door, 1570 is what is recommended for infiltration for this recommended for infiltration for this househouse
Determine course of action for homeDetermine course of action for home
Cfm50 x .7 = minimum ventilationCfm50 x .7 = minimum ventilation 1570 cfm50 x .7 = 1099 cfm501570 cfm50 x .7 = 1099 cfm50
If the blower door reads:If the blower door reads:– Above 1570 cfm then the house is too loose Above 1570 cfm then the house is too loose
and you would recommend air sealingand you would recommend air sealing
If the blower door reads:If the blower door reads:– Between 1570 cfm50 and 1099 cfm50, then the Between 1570 cfm50 and 1099 cfm50, then the
house is within the normal range for infiltration house is within the normal range for infiltration and ventilationand ventilation
If the blower door reads:If the blower door reads:– Below 1099 cfm50 then you need to Below 1099 cfm50 then you need to
mechanically ventilate the house using a hrv or mechanically ventilate the house using a hrv or equivalent device. The house is too tight at this equivalent device. The house is too tight at this point.point.