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Combining and adapting HVAC templates in EnergyPlus

asked 2015-08-21 05:22:24 -0500

gerald's avatar

updated 2015-08-24 03:52:50 -0500

I want to model a simple floor heating system in EnergyPlus (I am new to building simulation and need it for my thesis). Can I always start with this HVAC templates? Or do I need to use for example: ZoneHVAC:LowTemperatureRadiant:ConstantFlow? Or can I combine templates (for the plant loops) with special heating devices (like this LowTemperatureRadiant:ConstantFlow).

It is really hard to understand what a proper workflow should be. It would be very helpful if someone could suggest a workflow for implementing HVAC (Templates for thermostat, zone, Plant,etc.).

step 1 I implemented HVACTemplate:Zone:BaseboardHeat with HVACTemplate:Thermostat, HVACTemplate:Plant:HotWaterLoop, and HVACTemplate:Plant:Boiler.

Before I change to LowTemperatureRadiant - i tried to run the model with BaseboardHeat. I set the Thermodstat to constant heating setpoint 17°C - but the lowest zone air temperature is 12°C.

IDF file: weather file:

solution: increased the heating sizing factor to 2

Step 2: Now I deleted ZoneHVAC:Baseboard:RadiantConvective:Water and added ZoneHVAC:LowTemperatureRadiant:VariableFlow + Construction:InternalSource. I changed the equipment list, brachn list, Pump:VariableSpeed (I need a variable Flow), etc. But I get the following warnings:

Check input. Pump nominal flow rate is set or calculated = 0, for pump=HOT WATER LOOP HW SUPPLY PUMP SizePlantLoop: Calculated Plant Sizing Design Volume Flow Rate=[0.00] is too small And a Severe Node Connection Error, Node="8FF727 BASEBOARD HW INLET", The same node appears as a non-parent Inlet node more than once * ~~~ * Reference Object=ZONEHVAC:LOWTEMPERATURERADIANT:VARIABLEFLOW, Name=LOWTEMPRADIANT Do I have to implement new nodes for cooling?

I know that this is not a common way that I upload files – but I have to show the project team some results and I really want to use energyPlus in my further work (it is part of a big project).

IDF File: Thank you very much for your great help so far. Thank you very much.

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answered 2015-08-24 12:05:39 -0500

I can try to help you with your errors and the Lowtemperatureradiant object

Lets start with the node connection errors for the radiant floors you need 2 nodes for heating and 2 nodes for cooling. The heating nodes connect to the boiler loop and the cooling nodes connect to the cooling loop. If you don't have cooling you can leave that part of the object blank (you might need to fill in one or two items but the error files will let you know which those are, most importantly keep the cooling node names blank). The radiant object then needs to be listed on the equipment list for each room it is in.

Each radiant object needs to have a branch with the heating nodes and a separate branch with the cooling nodes (if you have cooling). These branches then need to be placed on the demand side of the heating loop for the hot side and the demand side of the cooling loop for the cold side, this is done in the objects Branchlist, Connector:Splitter, Connector:Mixer. (replace were the radiators had been put).

Finally the surfaces that have radiant floors indeed have to have Construction:InternalSource but they also need to be listed on ZoneHVAC:LowTemperatureRadiant:SurfaceGroup. That is the name of the surface and the percentage of that surface in the whole group that is radiant.

I am not sure about your pump flow rate but i would set it to autosize and go from there. it might just be an error because the radiant ceilings aren't connected up correctly.

I have drawn a node connection drawing with branches to try to help you understand how everything goes together.

image description

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Thank you so much! A few more questions: a) I deleted the branch: HotWaterloop Demand Bypass Branch - is that OK (if i have one zone)? b) Then i deleted "Demand Bypass Branch" in BranchList

c) But when i delete the Hot water loop Demand Splitter and Mixer (if there is no bypass and just 1 zone, i do not need a Splitter and Mixer right?) - then i got the Severe: There are multiple branches, yet no splitter. This is an invalid conf. Add a set of connectors, use put components on a single branch. If I add a Splitter and Mixer - it works. d) Do i need surfaceGroup if i have just one radSurface?

gerald's avatar gerald  ( 2015-08-25 04:11:29 -0500 )edit

Hi, I think as a rule in EnergyPlus don't delete. Even with one zone all the connectors and wrappers and so on need to be there. So i would put the "Hotwaterloop Demand Bypass branch" back in and add it back to the branchlist, i forgot to include it in the diagram above but both demand and supply need a bypass branch even if flow does not pass through it. also you will need to put the splitter and mixer back in. even with one zone you need all these things. Finally yes you will need a surface group even for one surface, it is how energyplus knows that surface is radiant in that zone.

Annie Marston's avatar Annie Marston  ( 2015-08-25 08:22:53 -0500 )edit

@gerald It does not hurt to use the radiant surface group, but it is allowable to put a single surface name in the "Surface Name or Radiant Surface Group Name" field if you have a single active surface in the zone.

MJWitte's avatar MJWitte  ( 2015-08-25 10:14:05 -0500 )edit

answered 2015-08-21 18:15:52 -0500

updated 2015-08-22 13:11:32 -0500

HVACTemplates are used to quickly create an HVAC system for a building with one or more zones. The only inputs required are zone name, specific schedules used to control the HVAC system, and minimal other inputs to describe the desired HVAC system.

To see how HVACTemplates work, review the example files with names starting with HVACTemplate*. I do not think a template exists for ZoneHVAC:LowTemperatureRadiant:ConstantFLow.

The current template expansion program supports the following objects. These are the plant, system, thermostat, and zone templates. Typically, one of each of these is required. The plant type is used when chilled or hot water loops are needed. If there are no plant loops, this template is not used. The system type is used for each HVAC system configured as air loop equipment. The thermostat type is used to populate the zones with a thermostat. And finally, the zone type is used for zone equipment in each zone.





Many other objects are created when using templates. For example, the HVACTemplate_5ZoneBaseboardHeat.idf file was modified (by removing 4 of the zone baseboard heat templates) to keep only a single zone template for the baseboard. This example system uses 4 template objects.


When this simulation is executed, the template objects will be expanded to create all required objects for the HVAC system specified. The expanded system will be saved in the expidf file and can be viewed after the simulation completes. Template objects in the input file will be commented out, and the objects added due to expansion are added at the end of the input file.

The first 4 objects below are the HVACTemplates in the original (modified) file. In the expidf file, these are commented out since they are no longer needed and have been replaced with the required EnergyPlus objects. It is apparent from this example that using templates can save a significant amount of time setting up the HVAC system.

!   HVACTemplate:Thermostat,
!     Heat Only,               !- Name
!     Htg-SetP-Sch,            !- Heating Setpoint Schedule Name
!     ,                        !- Constant Heating Setpoint {C}
!     No-Clg-SetP-Sch,         !- Cooling Setpoint Schedule Name
!     ;                        !- Constant Cooling Setpoint {C}
!   HVACTemplate:Zone:BaseboardHeat,
!     SPACE1-1,                !- Zone Name
!     Heat Only,               !- Template Thermostat Name
!     ,                        !- Zone Heating Sizing Factor
!     HotWater,                !- Baseboard Heating Type
!     ,                        !- Baseboard Heating Availability Schedule Name
!     autosize,                !- Baseboard Heating Capacity {W}
!     ,                        !- Dedicated Outdoor Air System Name
!     Flow/Person,             !- Outdoor Air Method
!     ,                        !- Outdoor Air Flow Rate per Person ...
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answered 2015-08-21 18:02:55 -0500

Radiant floor heat is not currently supported with an HVACTemplate object. The simplest approach would be to use HVACTemplate:Zone:BaseboardHeat with HVACTemplate:Thermostat, HVACTemplate:Plant:HotWaterLoop, and HVACTemplate:Plant:Boiler. See example file HVACTemplate-5ZoneBaseBoardHeat.idf

Run a simulation with that file, then rename the expidf output file to <newfilename>.idf and edit it to delete the baseboard heat and replace it with ZoneHVAC:LowTemperatureRadiant:ConstantFlow. (Search for ZoneHVAC:Baseboard:RadiantConvective:Water to find the places you need to change.) You will also need to add the low temp radiant objects, and the Construction:InternalSource (and change the construction name in the floor surface). See example file RadLoTempCFloTermReheat.idf

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@gerald Annie has covered this, but I just want to re-iterate here that you didn't need to change any branch list items (unless the names bothered you). You only needed to find each baseboard object's branch and substitute the low temperature radiant object type, name and node names. Same for the pump, just replace the object type in the branch object.

MJWitte's avatar MJWitte  ( 2015-08-25 10:17:30 -0500 )edit

answered 2015-08-21 18:31:34 -0500

Another option is to try to use OpenStudio ( They have several templates that will be probably helpful to get you started with energy modeling.

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Thank you. I did not found a template for floor heating systems (just VAV, etc.). Do you (or does anybody) maybe have an basic example in OS with floor heating systems? Would be so helpful!! Thank you very much.

gerald's avatar gerald  ( 2015-08-22 09:22:06 -0500 )edit

@Kyle Benne is the right person to answer this.

Mostapha Roudsari's avatar Mostapha Roudsari  ( 2015-08-23 10:00:00 -0500 )edit

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Asked: 2015-08-21 05:22:24 -0500

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Last updated: Aug 24 '15