HVAC System Diagram

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HVAC System Diagram. No outside air flow (exhaust or supply) via HVAC system. AirLoopHVAC:UnitaryHeatCool. Air Supply Inlet Node. Heating Coil Inlet Node. Cooling Coil Inlet Node. Air Supply Outlet Node. Air Demand Inlet Node. Living Supply Node. List: Living Supply Nodes. - PowerPoint PPT Presentation

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HVAC System DiagramAirLoopHVAC:UnitaryHeatCoolCoil:Cooling:DX:SingleSpeedCoil:Heating:GasFan:OnOffAir Supply Inlet NodeAir Supply Outlet NodeHeating Coil Inlet NodeCooling Coil Inlet NodeZone [Living]Living Zone Air NodeAirTerminal:SingleDuct:UncontrolledDXDehumidifier Outlet NodeList: Living Supply NodesList: Living Exhaust NodesDXDehumidifier Inlet NodeZone [RA Duct Zone]RA Plenum Air NodeLiving Return NodeAir Demand Outlet NodeSplitterAir Demand Inlet NodeLiving Supply NodePlenumZoneHVAC:Dehumidifier:DXSingle-Family Infiltration & Ventilation Modeling25 May 2011No outside air flow (exhaust or supply) via HVAC system1HVAC System Diagram with ERVAirLoopHVAC:UnitaryHeatCoolCoil:Cooling:DX:SingleSpeedCoil:Heating:GasFan:OnOffAir Supply Inlet NodeAir Supply Outlet NodeHeating Coil Inlet NodeCooling Coil Inlet NodeZone [Living]Living Zone Air NodeAirTerminal:SingleDuct:UncontrolledDXDehumidifier Outlet NodeList: Living Supply NodesList: Living Exhaust NodesDXDehumidifier Inlet NodeZone [RA Duct Zone]RA Plenum Air NodeLiving Return NodeAir Demand Outlet NodeSplitterAir Demand Inlet NodeLiving Supply NodePlenumZoneHVAC:Dehumidifier:DXSingle-Family Infiltration & Ventilation Modeling25 May 2011Outside air flow (supply and exhaust) via ERVFan:OnOffFan:OnOffERV Exhaust Fan Outlet NodeERV Exhaust Fan Inlet NodeERV Outside Air Inlet NodeERV Supply Fan Inlet NodeLiving Exhaust NodeERV Supply Fan Outlet Node2Infiltration CalculationsSingle-Family Infiltration & Ventilation Modeling25 May 2011EnergyManagementSystem:Program, InfiltrationProgram, Set Tdiff = Tin - Tout, Set DeltaT = @Abs Tdiff, Set c =0.0806596739779895, Set Cs =0.0808179140957512, Set Cw =0.151714102844197, Set n =0.67, Set sft =0.5039400176752, Set Qn = (((c*Cs*(DeltaT^n))^2)+(((c*Cw)*((sft*Vwind)^(2*n)))^2))^0.5, !Section above: !This is equation 41 + equation 42 from ASHRAE Fundamentals 2005 Ch 27 !"Enhanced Model. This section presents a simple, single-zone approach !to calculating air infiltration rates in houses based on the AIM-2 model !(Walker and Wilson 1998). The airflow rate due to infiltration is !calculated using: ! Qs = c * Cs * DeltaT^n (41) ! Qw = c * Cw (sU)^2n (42) ! where: Qs = stack airflow rate, m3s ! Qw = wind airflow rate, m3/s ! c = flow coefficient, m3/(s/Pa^n) ! Cs = stack coefficient, (Pa/K)^n ! Cw = wind coefficient, (Pa-s^2/m^2)^n ! s = shelter factor ! Several assumptions made when calculating Cs, Cw, s ! including: n = 0.67 ! Equation (39) then describes superposition for the total infiltration rate: ! Q = ((Qs^2)+(Qw^2))^0.5 Set Tdiff = Tin - Tout, Set DeltaT = @Abs Tdiff, Set QWH = WH_sch*0.025029576, Set Qrange = Range_sch*0.04719, Set Qdryer = Clothes_dryer_sch*0.04719, Set Qbath = Bath_sch*0.04719, Set Qu = QWH+Qrange+Qbath+Qdryer+DuctLeakOAMakeupFlowRate, Set Qb = 0, Set faneff_wh =0.28314, Set WholeHouseFanPowerOverride= (QWH*300)/faneff_wh, Set faneff_sp =0.28314, Set RangeHoodFanPowerOverride = (Qrange*300)/faneff_sp, Set BathExhaustFanPowerOverride = (Qbath*300)/faneff_sp, Set Infilflow = ((Qu^2) + (Qn^2))^0.5, Set InfMechVent = Qb + Infilflow; !Two lines above described by Equation (43) in ASHRAE Fundamentals 2005 Ch 27 !Says that you can combine residential infiltration and mechanical ventilation flows: ! Qcomb = Qbal + ((Qunbal^2)+(Qinfil^2))Qn = infiltration flowQu = unbalanced exhaust flow = QWH + Qrange + Qdryer + Q bath + DuctLeakage QWH = Whole house exhaust fan Qrange = Kitchen range hood Qbath = Bath point exhaust Qdryer = Dryer exhaust DuctLeakage = Calculated from DuctLeakageProgram Qb = balanced ventilation = 0InfMechVent = Total flowParameters to change infiltration rates3Building America House Simulation Protocol, pg 16: Additional air exchange whole-house mechanical ventilation shall be calculated assuming a single point exhaust ventilation system with the same ventilation rate used for the NCTH, up to a maximum value consistent with the rate recommended by ASHRAE 62.2. Whole-house mechanical ventilation air shall be added to the natural infiltration rate in quadrature, assuming no heat recovery. Ventilation fan energy use for the Benchmark shall be calculated using a fan efficiency of 0.5 W/cfm. In addition to whole-house ventilation, the Benchmark shall include a kitchen range hood, spot ventilation fan in each bathroom, and exhaust from the clothes dryer. The flow rates of the kitchen and bathroom fans shall be the same as those in the NCTH, and their efficiency shall be assumed to operate 60 min/day (between 6:00 pm and 7:00 pm), and each bathroom fan (including those in central restrooms) is assumed to operate 60 minutes per day (between 7:00 am and 8:00 am). The clothes dryer fan will operate for 60 minutes per day between 11:00 am and 12:00 pm. Interactive effects between these spot exhaust ventilation fans and natural infiltration shall be included in the analysis.

Ventilation Components & SchedulesSingle-Family Infiltration & Ventilation Modeling25 May 20114ASHRAE 62.2 Ventilation Requirements

Qfan = fan flow rate in L/s; Afloor = floor area in m2; Nbr = number of bedroomsFor Nbr = 3, Afloor = 222 m2 (2400 ft2): Qfan = 25.1 L/s = 0.025 m3/s= 54 cfmSingle-Family Infiltration & Ventilation Modeling25 May 2011ASHRAE 62.2-2003, Section 4.1: A mechanical exhaust system, supply system, or combination thereof shall be installed for each dwelling unit to provide whole-building ventilation with outdoor air each hour at no less than the rate specified in Table 4.1a and Table 4.1b, or, equivalently, Equations 4.1a and 4.1b, based on the floor area of the conditioned space and number of bedrooms.5Modeling Results Exhaust Flows Summer Design DaySingle-Family Infiltration & Ventilation Modeling25 May 2011

6Modeling Results Qu & Qn Summer Design DaySingle-Family Infiltration & Ventilation Modeling25 May 2011

7Modeling Results Total Flow Summer Design DaySingle-Family Infiltration & Ventilation Modeling25 May 2011

8Modeling Results Hours not meeting ASHRAE 62.2-2003Single-Family Infiltration & Ventilation Modeling25 May 2011RunHours not met (Qn)Hours not met (Total Flow)CHI_ICF4in_BaseInfil_GndTemps5450CHI_ICF4in_Infil_a_GndTemps7760CHI_ICF4in_Infil_b_GndTemps7800PHX_ICF4in_BaseInfil_GndTemps22690PHX_ICF4in_Infil_a_GndTemps30660PHX_ICF4in_Infil_b_GndTemps301909Natural Ventilation CalculationsSingle-Family Infiltration & Ventilation Modeling25 May 2011EnergyManagementSystem:Program, NaturalVentilationProgram, Set Tdiff = Tin - Tout, Set DeltaT = @Abs Tdiff, Set Phiin = @RhFnTdbWPb Tin Win Pbar, ! RhFnTdbWPb: Calculates RH (fraction) from DB, Humidity Ratio, Barometric Pressure Set Hin = @HFnTdbRhPb Tin Phiin Pbar, ! HFnTdbW: Calculates Enthalpy of moist air (J/kg) from DB and Humidity Ratio Set NVArea =12006.190854504, !Not clear how this number is determined, but it is cm^2 Set Cs =0.0001792604077892, Set Cw =0.0002821728237939, Set MaxNV =2.8993536, Set SGNV = (NVAvail*NVArea)*((((Cs*DeltaT)+(Cw*(Vwind^2)))^0.5)/1000), !Line above based on equation (40) from ASHRAE Fundamentals 2005 Ch 27 !This is the basic model for calculating the airflow rate due to infiltration ! Q = AL/1000((Cs*DeltaT)+(Cw(U^2))^0.5 ! where: Q = airflow rate m3/s ! AL = effective air leakage area, cm2 ! DeltaT = Avg indoor-outdoor temp difference, K ! Cw = wind coefficient ! U = avg windspeed measured at local weather station If Wout < 0.0155 && Phiin < 0.70 && Tin > NVSP, !Line above sets outdoor conditions for nat vent !Wout is Outdoor Humidity Ratio; Phiin is RH; Tin is Zone MAT; NVSP is NatVentTemp Schedule Value. Set NVadj1 = (Tin - NVSP)/(Tin - Tout), Set NVadj2 = @Min NVadj1 1, Set NVadj3 = @Max NVadj2 0, Set NVadj = SGNV*NVadj3, Set NatVentFlow = @Min NVadj MaxNV, Else, Set NatVentFlow = 0, EndIf;Qn = infiltration flowQu = unbalanced exhaust flow = QWH + Qrange + Qdryer + Q bath + DuctLeakage QWH = Whole house exhaust fan Qrange = Kitchen range hood Qbath = Bath point exhaust Qdryer = Dryer exhaust DuctLeakage = Calculated from DuctLeakageProgram Qb = balanced ventilation = 0InfMechVent = Total flow10Modeling Results BEOpt Vent OptionsSingle-Family Infiltration & Ventilation Modeling25 May 2011

11Modeling Results BEOpt NatVent OptionsSingle-Family Infiltration & Ventilation Modeling25 May 2011

12Modeling Results BEOpt Slab OptionsSingle-Family Infiltration & Ventilation Modeling25 May 2011

13Modeling Results NatVentSingle-Family Infiltration & Ventilation Modeling25 May 2011

This report variable represents the sensible heating energy in Joules that is actually supplied by the system to that zone for the timestep reported. This is the sensible heating rate multipled by the simulation timestep.

Zone/Sys Sensible Heating (and Cooling) Energy all report the heating or cooling delivered by the HVAC system to a zone. These values are calculated by multiplying the supply air mass flow rate by the difference between the supply air temperature and the zone air temperature. This does not always indicate the operation of heating or cooling coils. For example, cooling will be reported if the supply air is cooled due to the introduction of outside air, event if all coils are off. I/O pg. 168 14Modeling Results NatVentSingle-Family Infiltration & Ventilation Modeling25 May 2011

15Modeling Results NatVentSingle-Family Infiltration & Ventilation Modeling25 May 2011

16Modeling Results NatVentSingle-Family Infiltration & Ventilation Modeling25 May 2011

This is the total (sensible plus latent) cooling output of the