Lecture 19: HVAC Outside Air Systems and Modeling Guidelines Material prepared by GARD Analytics, Inc. and University of Illinois at Urbana-Champaign under contract to the National Renewable Energy Laboratory. All material Copyright U.S.D.O.E. - All rights reserved

2 Purpose of this Lecture  Discuss Outside Air IAQ requirements force us to draw fresh air in from the outside environment Outside air (OA) can have a significant impact on the building energy requirements  Show how OA is specified in EnergyPlus

3 Keywords Covered in this Lecture  Air Loop Equipment List  Outside Air System  Outside Air Mixer  Controller:Outside Air  Outside Air Inlet Node List  Review of other related keywords

4 Components: Special Case - Outside Air System OUTSIDE AIR SYSTEM is a subsystem component  OA System Controller List  OA System Equipment List  OA System Availability Manager List

5 OA System Equipment List  System component type outside air mixer, coil, heat exchanger  System component name  Repeat for each air loop component

6 Air Loop Equipment List - Example AIR LOOP EQUIPMENT LIST, OA Sys 1 Equipment, !- Name OUTSIDE AIR MIXER, !- KEY--System Component 1 OA Mixing Box 1; !- Component Name 1

7 Outside Air System - Example OUTSIDE AIR SYSTEM, OA Sys 1, !- Name OA Sys 1 Controllers, !- Name: Controller List OA Sys 1 Equipment, !- Name of an Air Loop Equipment List VAV Sys 1 Avail List; !- Name of a System Availability Manager List

8 Outside Air Mixer  Mixed_Air_Node  Outside_Air_Stream_Node  Relief_Air_Stream_Node  Return_Air_Stream_Node

9 Outside Air Mixer - Example OUTSIDE AIR MIXER, OA Mixing Box 1, !- Name Mixed Air Node 1, !- Mixed_Air_Node Outside Air Inlet Node 1, !- Outside_Air_Stream_Node Relief Air Outlet Node 1, !- Relief_Air_Stream_Node VAV Sys 1 Inlet Node; !- Return_Air_Stream_Node

10 CONTROLLER LIST, OA Sys 1 Controllers, !- Name CONTROLLER:OUTSIDE AIR, !- Controller Type 1 OA Controller 1; !- Controller Name 1 Outside Air Mixer – Controller List

11 Controller:Outside Air  Control_Node  Actuated_Node  Minimum outside air flow rate  Maximum outside air flow rate  Temperature limit  Temperature lower limit

12 Controller:Outside Air - Example CONTROLLER:OUTSIDE AIR, OA Controller 1, !- Name ECONOMIZER, !- EconomizerChoice NO RETURN AIR TEMP LIMIT, !- ReturnAirTempLimit NO RETURN AIR ENTHALPY LIMIT, !- ReturnAirEnthalpyLimit NO LOCKOUT, !- Lockout FIXED MINIMUM, !- MinimumLimit Mixed Air Node 1, !- Control_Node Outside Air Inlet Node 1, !- Actuated_Node autosize, !- min outside air flow rate {m3/s} autosize, !- max outside air flow rate {m3/s} 19., !- temperature limit {C} 4., !- temperature lower limit {C} 0.0, !- enthalpy limit {J/kg} Relief Air Outlet Node 1, !- Relief_Air_Outlet_Node VAV Sys 1 Inlet Node, !- Return_Air_Node Min OA Sched; !- Minimum Outside Air Schedule Name

13 TermReheat with Outside Air Example  Air Loop contains the Mixed Air System

14 TermReheat Main Branch with OA System BRANCH, Air Loop Main Branch, !- Branch Name 1.3, !- Maximum Branch Flow Rate {m3/s} OUTSIDE AIR SYSTEM, !- Comp1 Type OA Sys 1, !- Comp1 Name VAV Sys 1 Inlet Node, !- Comp1 Inlet Node Name Mixed Air Node, !- Comp1 Outlet Node Name PASSIVE, !- Comp1 Branch Control Type FAN:SIMPLE:ConstVolume, !- Comp2 Type Supply Fan 1, !- Comp2 Name Mixed Air Node, !- Comp2 Inlet Node Name

15 TermReheat Outside Air Node List OUTSIDE AIR INLET NODE LIST, OutsideAirInletNodes; !- 1st Node name or node list name NODE LIST, OutsideAirInletNodes, !- Node List Name Outside Air Inlet Node 1; !- Node_ID_1

16 TermReheat Outside Air System OUTSIDE AIR SYSTEM, OA Sys 1, !- Name OA Sys 1 Controllers, !- Name: Controller List OA Sys 1 Equipment, !- Name of an Air Loop Equipment List VAV Sys 1 Avail List; !- Name of a System Availability Manager List

17 TermReheat Outside Air Controller List CONTROLLER LIST, OA Sys 1 Controllers, !- Name CONTROLLER:OUTSIDE AIR, !- Controller Type 1 OA Controller 1; !- Controller Name 1

18 TermReheat Outside Air Equipment List AIR LOOP EQUIPMENT LIST, OA Sys 1 Equipment, !- Name OUTSIDE AIR MIXER, !- KEY--System Component 1 OA Mixing Box 1; !- Component Name 1

19 TermReheat Outside Air Controller CONTROLLER:OUTSIDE AIR, OA Controller 1, !- Name ECONOMIZER, !- EconomizerChoice NO RETURN AIR TEMP LIMIT, !- ReturnAirTempLimit NO RETURN AIR ENTHALPY LIMIT, !- ReturnAirEnthalpyLimit NO LOCKOUT, !- Lockout FIXED MINIMUM, !- MinimumLimit Mixed Air Node 1, !- Control_Node Outside Air Inlet Node 1, !- Actuated_Node 0.468, !- minimum outside air flow rate {m3/s} 1.56, !- maximum outside air flow rate {m3/s} 19., !- temperature limit {C} 4., !- temperature lower limit {C} 0.0, !- enthalpy limit {J/kg} Relief Air Outlet Node 1, !- Relief_Air_Outlet_Node VAV Sys 1 Inlet Node, !- Return_Air_Node Min OA Sched; !- Minimum Outside Air Schedule Name

20 TermReheat Outside Air Mixer OUTSIDE AIR MIXER, OA Mixing Box 1, !- Name Mixed Air Node 1, !- Mixed_Air_Node Outside Air Inlet Node 1, !- Outside_Air_Stream_Node Relief Air Outlet Node 1, !- Relief_Air_Stream_Node VAV Sys 1 Inlet Node; !- Return_Air_Stream_Node

21 Outdoor Air Economizer  TermReheatOA.idf example file CONTROLLER:OUTSIDE AIR, OA Controller 1, !- Name ECONOMIZER, !- EconomizerChoice NO RETURN AIR TEMP LIMIT, !- ReturnAirTempLimit NO RETURN AIR ENTHALPY LIMIT, !- ReturnAirEnthalpyLimit NO LOCKOUT, !- Lockout FIXED MINIMUM, !- MinimumLimit Mixed Air Node, !- Control_Node Outside Air Inlet Node, !- Actuated_Node , !- minimum outside air flow rate {m3/s} 1.3, !- maximum outside air flow rate {m3/s} 19., !- temperature limit {C} 4., !- temperature lower limit {C} 0.0, !- enthalpy limit {J/kg} Relief Air Outlet Node, !- Relief_Air_Outlet_Node VAV Sys 1 Inlet Node; !- Return_Air_Node

22 Outdoor Air Economizer (cont’d)  Scheduled mixed air setpoint SET POINT MANAGER:SCHEDULED, Mixed Air Temp Manager, !- Name TEMP, !- Control variable Seasonal Reset Mixed Air Temp Sch, !- Schedule Name Mixed Air Nodes; !- Name of the set point Node List NODE LIST, Mixed Air Nodes, !- Node List Name Mixed Air Node; !- Node_ID_1

23 Outdoor Air Economizer (cont’d)  Mixed air setpoint adjusted for fan heat SET POINT MANAGER:SCHEDULED, Supply Air Temp Manager 1, !- Name TEMP, !- Control variable Seasonal Reset Supply Air Temp Sch, !- Schedule Name Supply Air Temp Nodes 1; !- Name of the set point Node List SET POINT MANAGER:MIXED AIR, Mixed Air Temp Manager 1, !- Name TEMP, !- Control variable: VAV Sys 1 Outlet Node, !- reference set point node name Main Heating Coil 1 Outlet Node, !- fan inlet node name VAV Sys 1 Outlet Node, !- fan outlet node name Mixed Air Node 1; !- Name of the set point Node or Node List NODE LIST, Supply Air Temp Nodes 1, !- Node List Name VAV Sys 1 Outlet Node; !- Node_ID_1

24 Economizer with Furnace/DX  Furnace/DX does not set a supply air setpoint  Must use setpoint managers to establish a setpoint

25 Summary  Introduction of outside air into a forced air system is necessary to meet indoor air quality (IAQ) standards  Outside air (mixing box) in EnergyPlus is a component on an air loop branch  Outside air system also contains controllers that can be operated in economizer mode