Lecture 15: Air Primary Loops and Controls Material prepared by GARD Analytics, Inc. and University...
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Transcript of Lecture 15: Air Primary Loops and Controls Material prepared by GARD Analytics, Inc. and University...
Lecture 15: Air Primary Loops and Controls
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
Gain an understanding of how to: Define primary air loops in EnergyPlus Control their operation and
availability for conditioning thermal zones
3
Keywords Covered in this Lecture
Air Primary LoopSystem Availability Manager ListSystem Availability
Manager:ScheduledSystem Availability Manager:Night
CycleController ListController:Simple
4
Describing a Central Forced Air System
Can be thought of as an “Air Loop” with 2 “sides”: Supply side: air primary loop and its
associated objects central fans, coils, etc.
Demand side: controlled zone equip configuration and its associated objects air terminal units, fan coils, etc.
5
Describing a Central Forced Air System (cont’d)When we say “Air Loop” we will
normally mean the supply side of the overall air loop
“Zone Equipment” will mean the demand side: all the stuff specific to a zone
If no central air system, then there will be only zone equipment
6
Describing a Central Forced Air System (cont’d)
North
Zone
East
Zone
Resistive
Zone
Supply Fan
Ret
urn
Air
Mix
er
Zo
ne A
ir Sp
litter
Cooling CoilCC
VAV Box:ReHeat
VAV Box:ReHeat
Mixed OutsideAir Box
Relief Air
Outside Air
VAV Box:ReHeat
Supply Side/AirPrimary Loop
Demand Side/ZoneEquipment
7
Air Loop Simulation
Simulates central air distribution, mixing, and conditioning Equipment: supply & return fans,
central heating and cooling coils, heat recovery, mixed air box
Control: supply air temperature, outside air economizer
8
Hot Branch
Cold Branch
Air Loop Layout
Main Supply Branch
Splitter
Zone Equipment Group
Zone Splitter
Zones
Zone Splitter
Zone Mixer
Zone Equipment
Group Inlets
Zone EquipGroup Outlet
9
Air Loop Layout (cont’d)
Supply Fan
Mixed OutsideAir Box
Relief Air
Outside Air
Heating/CoolingCoil
Supply Fan
Relief Air
Outside Air
Heating/CoolingCoil
Air Loop Outlet NodeAir Loop Inlet Node
Zone Equip Inlet NodeZone Equip Outlet Node
10
Air Loop Syntax Map Air Loop Input Structure/Map
Air Primary Loop
data
Controller List System Availability Manager List Branch List Supply Air Controller List
component controllers in order of priority; defined by CONTROL:... syntax
System Availability Manager List managers such as:
System Availability Manager:Scheduled
etc.
Branch List
branch name 1, branch name 2, …..
Connector List
Connector List
Connector type, connector name
11
Air Primary Loop
Controller ListSystem Availability Manager ListBranch ListConnector ListConnection to Zone Equipment
ReturnAir AirLoop Inlet Node ZoneEquipGroup Outlet Node SupplyAirPath ZoneEquipGroup Inlet Nodes AirLoop Outlet Nodes
12
Air Primary Loop - Example
AIR PRIMARY LOOP,
Unitary System, !- Primary Air Loop Name
, !- Name: Controller List
Avail List, !- Name: System Availability Manager List
autosize, !- Primary air design flow rate {m3/s}
Air Loop Branches, !- Air Loop Branch List Name
, !- Air Loop Connector List Name
Air Loop Inlet Node, !- ReturnAir AirLoop Inlet Node
ZONE EQUIP OUTLET NODE, !- ZoneEquipGroup Outlet Node
Zone Equipment Inlet Node,!- SupplyAirPath ZoneEquipGroup In Nodes
Air Loop Outlet Node; !- AirLoop Outlet Nodes
13
System Control
High Level Similar to an energy management
system Set Point Managers
algorithms establish fluid loop set points Availability Managers
make global on/off decisions
14
System Control (cont’d)
Component Control Controllers
sense state at one point in system control flow at another point to match set
point Integrated control
control integrated within component
15
System Control (cont’d)
Plant: component sequencing & load management
Control is ideal PI/PID control is not modeled – would
require shorter time steps
16
System Availability Managers
Scheduled System availability determined by an
on/off schedule
Night Cycle Used to cycle an air system on when
one or more zones becomes too hot or too cold
17
System Availability Manager List
Lists all of the applicable system availability managers for a given air loop
SYSTEM AVAILABILITY MANAGER LIST,
Furnace- Avail List, !- Name
SYSTEM AVAILABILITY MANAGER:SCHEDULED, !- Type
Furnace- Avail; !- System Availability Manager Name 1
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System Availability Manager:Scheduled
Simple on/off schedule
SYSTEM AVAILABILITY MANAGER:SCHEDULED,
Furnace- Avail, !- Name
FanAndCoilAvailSched; !- Schedule name
19
System Availability Manager:Night Cycle
Applicability schedule nameFan schedule nameControl type
Stay Off, Cycle On Any, Cycle On Control Zone, Cycle On Any - Zone Fans Only
Thermostat on/off toleranceCycling run timeControl zone name
20
System Availability Manager:Night Cycle-
Example SYSTEM AVAILABILITY MANAGER:NIGHT CYCLE, VAV Sys 1 Avail, !- Name SysAvailApplicSch, !- Applicability schedule name FanAvailSched, !- Fan schedule name Cycle On Any, !- Control type 4.0, !- thermostat on/off tolerance {deltaC} 7200.; !- Cycling run time {s}
21
Set Point Managers
Scheduled Uses a schedule to determine one or more
set points
Outside Air Sets the supply air temperature according
to the outside air temperature using a reset rule
Reset schedule determined by the supply air set point temperature at the outside high and low temperature
22
Set Point Managers (cont’d)
Single Zone Reheat Calculates a set point temperature for
the supply air that will satisfy the load of a controlled zone
Single Zone Minimum Humidity Calculates the supply air humidity
ratio needed to maintain the zone relative humidity at or above a given set point
23
Set Point Managers (cont’d)
Mixed Air Used to establish a temperature set
point at the mixed air node Set point must take into account any
downstream system fan heat Outside air controller operates the
outside air damper to meet this set point for economizer
24
Controllers
Simple Controls variable at one node based on the
condition at another node For a cooling coil, the control node might be
the outlet air temperature while the actuated variable is the flow rate through the coil
Outside Air Controls mixed air box to use outside air for
free cooling whenever possible
25
Controller List
Repeat for each controller
CONTROLLER LIST,
VAV Sys 1 Controllers, !- Name
Controller:Simple, !- Controller Type 1
Central Cooling Coil Controller 1, !- Controller Name 1
Controller:Simple, !- Controller Type 2
Central Heating Coil Controller 1; !- Controller Name 2
26
Controller:Simple
Control_Node really the sensed node
Actuator_NodeController convergence toleranceMax actuated flowMin actuated flowAction
Reverse for cooling Normal for heating
27
Controller:Simple - Example
CONTROLLER:SIMPLE,
Central Heating Coil Controller 1, !- Name
TEMP, !- Control variable
Normal, !- Action
FLOW, !- Actuator variable
VAV Sys 1 Outlet Node, !- Control_Node
Main Heating Coil 1 Water Inlet Node, !- Actuator_Node
0.002, !- Controller Convergence Tolerance: delta from setpoint
autosize, !- Max Actuated Flow {m3/s}
0.0; !- Min Actuated Flow {m3/s}
Action is “Normal” for heating, “Reverse” for cooling.
28
Summary
Central forced air systems in EnergyPlus consist of an “air loop” (supply side) and a “zone equipment loop” (demand side)
Primary air loop description contains: controller list, availability manager, branch list, and connection information
Setpoint manager used by controllers to calculate current setpoint for various HVAC components