Lecture 19: HVAC Outside Air Systems and Modeling Guidelines

Material prepared by GARD Analytics, Inc. and University of Illinoisat Urbana-Champaign under contract to the National Renewable Energy

Laboratory. All material Copyright 2002-2003 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 ListOutside Air SystemOutside Air MixerController:Outside AirOutside Air Inlet Node ListReview of other related keywords

4

Components: Special Case - Outside Air System

OUTSIDE AIR SYSTEM is a subsystem component

OA System Controller ListOA System Equipment ListOA 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_NodeOutside_Air_Stream_NodeRelief_Air_Stream_NodeReturn_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_NodeActuated_NodeMinimum outside air flow rateMaximum outside air flow rateTemperature limitTemperature 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

North

Zone

East

Zone

Resistive

Zone

Supply FanR

etu

rn A

ir M

ixe

r

Zo

ne A

ir Sp

litter

CC

VAV Box:ReHeat

VAV Box:ReHeat

Mixed OutsideAir Box

Relief Air

Outside Air

VAV Box: ReHeat

North

Zone

East

Zone

Resistive

Zone

Supply FanR

etu

rn A

ir M

ixe

r

Zo

ne A

ir Sp

litter

CC

VAV Box:ReHeat

VAV Box:ReHeat

Mixed OutsideAir Box

Relief Air

Outside Air

VAV Box: ReHeat

Air Loop contains the Mixed Air System

14

TermReheat Main Branch with OA

SystemSupply Fan

CCMixed OutsideAir Box

Relief Air

Outside AirSupply Fan

CCMixed OutsideAir Box

Relief Air

Outside Air

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< cooling coil >

15

TermReheat Outside Air Node List

Mixed OutsideAir Box

Relief Air

Outside Air

Mixed OutsideAir Box

Relief Air

Outside Air

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

Mixed OutsideAir Box

Relief Air

Outside Air

Mixed OutsideAir Box

Relief Air

Outside Air

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

Mixed OutsideAir Box

Relief Air

Outside Air

Mixed OutsideAir Box

Relief Air

Outside Air

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

Mixed OutsideAir Box

Relief Air

Outside Air

Mixed OutsideAir Box

Relief Air

Outside Air

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

Mixed OutsideAir Box

Relief Air

Outside Air

Mixed OutsideAir Box

Relief Air

Outside Air

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 0.4333, !- 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