HB-Legacy VRF+DOAS seems to be causing an error?

Hi all,

Not sure if this is already a known issue or not, thought I’d post anyway though:

Using Honeybee-Legacy, I’m running into an error when trying to apply the ‘VRF+DOAS’ mech type to a zone. Example here with simple single zone - all the other types work fine (PTHP for instance):

But if I switch it to ‘VRF+DOAS’ it throws an error:


in.err message below:

Program Version,EnergyPlus, Version 9.3.0-baff08990c, YMD=2021.01.26 15:54,
       ************* Beginning Zone Sizing Calculations
       ** Warning ** ProcessScheduleInput: Schedule:Constant="ALWAYS OFF DISCRETE", Blank Schedule Type Limits Name input -- will not be validated.
       ** Warning ** ProcessScheduleInput: Schedule:Constant="ALWAYS ON CONTINUOUS", Blank Schedule Type Limits Name input -- will not be validated.
       ** Warning ** GetHTSurfaceData: Surfaces with interface to Ground found but no "Ground Temperatures" were input.
       **   ~~~   ** Found first in surface=ZONE_0_SRF_4
       **   ~~~   ** Defaults, constant throughout the year of (18.0) will be used.
       ************* Beginning System Sizing Calculations
       ** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF HEAT PUMP - 1" curve values
       **   ~~~   ** ... Cooling Capacity Ratio Modifier Function of Low Temperature Curve Name = AIR CONDITIONER VARIABLE REFRIGERANT FLOW 1 VRFCOOLCAPFT output is not equal to 1.0 (+ or - 10%) at rated conditions.
       **   ~~~   ** ... Curve output at rated conditions = 1.136
       ** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF HEAT PUMP - 1", invalid
       **   ~~~   ** ...Cooling Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name = AIR CONDITIONER VARIABLE REFRIGERANT FLOW 1 COOLINGEIRLOWPLR has out of range value.
       **   ~~~   ** ...Curve minimum value of X = 0.500 must be <= Minimum Heat Pump Part-Load Ratio = 0.250.
       ** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF HEAT PUMP - 1", invalid
       **   ~~~   ** ...Heating Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name = AIR CONDITIONER VARIABLE REFRIGERANT FLOW 1 HEATINGEIRLOWPLR has out of range value.
       **   ~~~   ** ...Curve minimum value of X = 0.500 must be <= Minimum Heat Pump Part-Load Ratio = 0.250.
       ** Warning ** ZoneTerminalUnitList "VRF HEAT PUMP - 1 TERMINAL LIST"
       ** Warning ** ...Only 1 Terminal Unit connected to system and heat recovery is selected.
       **   ~~~   ** ...Heat recovery will be disabled.
       **  Fatal  ** GetVRFInput: Errors found in getting AirConditioner:VariableRefrigerantFlow system input. Preceding condition(s) causes termination.
       ...Summary of Errors that led to program termination:
       ..... Reference severe error count=0
       ..... Last severe error=
       ************* Warning:  Node connection errors not checked - most system input has not been read (see previous warning).
       ************* Fatal error -- final processing.  Program exited before simulations began.  See previous error messages.
       ************* EnergyPlus Warmup Error Summary. During Warmup: 0 Warning; 0 Severe Errors.
       ************* EnergyPlus Sizing Error Summary. During Sizing: 8 Warning; 0 Severe Errors.
       ************* EnergyPlus Terminated--Fatal Error Detected. 8 Warning; 0 Severe Errors; Elapsed Time=00hr 00min  0.89sec

Has anyone else run into this issue? As I said, all the other mech items seem to work fine - its just this one that is causing an issue. Has anyone found a work around? Or am I supposed to be setting another value someplace in order to make this type of system work properly?

thanks very much for any help! (example. gh attached)
@edpmay

VRF_and_DOAS_Error.gh (539.2 KB)

@edpmay ,I’m facing the same issue, have you find the solution yet? @MingboPeng you know what happened?

I thought it is caused by the empty of the Field: Zone Name for Master Thermostat Location. Group – Variable Refrigerant Flow Equipment: Input Output Reference — EnergyPlus 9.5

When the heat pump is connected to multiple zone terminal units, one terminal unit must be selected as the master thermostat.

But with a re-run idf, still get the error
Ironbug_HVAC_16_VRF_DOAS.gh (688.4 KB)

if I’m not mistaken:
This issue is resolved via using LBT 1.x,
link to from what I gather is most up to date ironbug that works with 1.x as well as contains EMS features
See below image: Tried to re-do what you had in there in legacy bugs with the new:

That’s the right idea @TrevorFedyna .

The performance curves that were used for the VRF HVAC template in Legacy were really far from reality. It looks like EnergyPlus got wise and added some checks that bring these poor assumptions to the forefront of the simulation outputs.

The performance curves used for the VRF systems in LBT 1.3 are MUCH more realistic than those used in Legacy because the come from openstudio-standards instead of the random Openstudio measure that I pulled those legacy performance curves from. So you should just use the LBT plugin if you need to simulate a VRF system.

Or you could use Ironbug to build a custom VRF systems with your own performance curves.

To conenct the detailed modell of VRF+DOAS with LBT model, I tried this first, haha

thanks @TrevorFedyna to lead me here IronBug Air Source Heat Pump - #10 by MingboPeng @MingboPeng 's new example gived me the right route map

Ironbug_HVAC_16_VRF_DOAS_updated with LBT.gh (81.5 KB)

Using templates method is working now, but with detailed modelling I still get this:

  1. Solution exception: ** Fatal ** GetVRFInput: Errors found in getting AirConditioner:VariableRefrigerantFlow system input. Preceding condition(s) causes termination.

Can you share the preceding conditions in the *.err? Don’t really have much to go off of with just the end of the error msg

eplusout.err (3.9 KB)
@TrevorFedyna here is the err file.

Thanks! I was afk and unable to look at the .gh

AH okay: So you need additional Object params component:


Ironbug_HVAC_16_VRF_DOAS_TF_EDITS.gh (192.3 KB)
see attached: I used @MingboPeng example DOAS+VRF VRF params component to… save time as


Theres alot going on for VRF’s

But: at a minimum, if you want to as @chris said: do your own VRF with Ironbug: these inputs called out in the *.err for invalid performance curves should be enough at a minimum in terms of user input:

 ** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF" curve values
   **   ~~~   ** ... Cooling Capacity Ratio Modifier Function of Low Temperature Curve Name = AIR CONDITIONER VARIABLE REFRIGERANT FLOW 1 VRFCOOLCAPFT output is not equal to 1.0 (+ or - 10%) at rated conditions.
   **   ~~~   ** ... Curve output at rated conditions = 1.136
   ** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF", invalid
   **   ~~~   ** ...Cooling Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name = AIR CONDITIONER VARIABLE REFRIGERANT FLOW 1 COOLINGEIRLOWPLR has out of range value.
   **   ~~~   ** ...Curve minimum value of X = 0.500 must be <= Minimum Heat Pump Part-Load Ratio = 0.250.
   ** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF", invalid
   **   ~~~   ** ...Heating Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name = AIR CONDITIONER VARIABLE REFRIGERANT FLOW 1 HEATINGEIRLOWPLR has out of range value.
   **   ~~~   ** ...Curve minimum value of X = 0.500 must be <= Minimum Heat Pump Part-Load Ratio = 0.250.
   **  Fatal  ** GetVRFInput: Errors found in getting AirConditioner:VariableRefrigerantFlow system input. Preceding condition(s) causes termination.

There are some curve tools in E+ directory, for me it’s here: C:\EnergyPlusV9-5-0\PreProcess\HVACCurveFitTool

as well as some excel tools from designbuilder website freely downloadable

I see, I was hoping the model can work with some reasonable default parameters. So you mean I need to confige the whole parameters of the VRF system even the curves.

This is the bare minimum use of DOAS+VRF via Honeybee only:


For minimum IronBug VRF inputs:
These Should be the minimum required performance curve inputs:

** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF" curve values
   **   ~~~   ** ... Cooling Capacity Ratio Modifier Function of Low Temperature Curve Name = AIR CONDITIONER VARIABLE REFRIGERANT FLOW 1 VRFCOOLCAPFT output is not equal to 1.0 (+ or - 10%) at rated conditions.
   **   ~~~   ** ... Curve output at rated conditions = 1.136
   ** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF", invalid
   **   ~~~   ** ...Cooling Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name = AIR CONDITIONER VARIABLE REFRIGERANT FLOW 1 COOLINGEIRLOWPLR has out of range value.
   **   ~~~   ** ...Curve minimum value of X = 0.500 must be <= Minimum Heat Pump Part-Load Ratio = 0.250.
   ** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF", invalid
   **   ~~~   ** ...Heating Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name = AIR CONDITIONER VARIABLE REFRIGERANT FLOW 1 HEATINGEIRLOWPLR has out of range value.
   **   ~~~   ** ...Curve minimum value of X = 0.500 must be <= Minimum Heat Pump Part-Load Ratio = 0.250.
   **  Fatal  ** GetVRFInput: Errors found in getting AirConditioner:VariableRefrigerantFlow system input. Preceding condition(s) causes termination.

publication on the creation of VRF perfomance curves
VRF’s are a beast: unsolicited $0.02, I’d use the Honeybee DOAS+VRF if unsure on explicit inputs to use.
I’ve definitely been through the ringer come VRF’s before; and am a bit weary of them come setting up all of the performance curves and the likes.

I’m trying this just because the air path of the DOAS is litte tricky, it has central return path in corridor and bath room. I don’t think the DOAS+VRF template is working in this way, maybe it still needs the help of AFN. I’m not sure.

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