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Thanks for your opinion. This is a requirement for the baseline case. We are happy when the baseline case consumes more

I would just like to know the correct interpretation of ASHRAE 90.1 Appendix G. Preheat coil is required in the baseline

Say, OA is 0ºC (32ºF), and the indoor heating setpoint is 20ºC (68ºF). The preheat coil heats the air up to 9ºC (48ºF).

Sorry if the link is wrong. I meant to ask about Airterminal:SingleDuct:VAV:Reheat.

A bug report

EnergyPlus I/O Reference states as follows:

Crankcase Heater Power per Compressor: Crankcase heater electrical consumption is applied only when the compressor is off or is applied during the off cycle when the compressor is cycling below the Minimum Heat Pump Part-Load Ratio.

Maximum Outdoor Dry-bulb Temperature for Crankcase Heater: This numeric field defines the maximum outdoor temperature, in degrees Celsius, below which the crankcase heater will operate.

However, what I observed is the opposite. Crankcase heater electrical consmption is applied when both of the following conditions are met;

1. The compressor is ON (regardless of cooling or heating mode).
2. The outdoor temperature is below the maximum outdoor dry-bulb temperature setpoint.

It would be nice to see more crankcase heater operation options in the future, but for now, I think the I/O Reference is more relevant. Crankcase heater electric consumption should be applied when the compressor is OFF.

The bug can be easily reproduced with ExampleFiles e.g., VariableRefrigerantFlow_5Zone.idf (V25-2-0).

Thank you! I'll check the operation again with V26-1-0.

The only case that didn't work well was setting the air terminal min air flow fraction to 0 (although that's unlikely in

Thank you for the answer. I explored a bit. For heating sizing runs, the air terminal air flow rate did not increase wit

A similar report is found on Github, but it has not been addressed enough. https://github.com/NatLabRockies/EnergyPlus/

VRF Crankcase Heater Operation A bug report EnergyPlus I/O Reference states as follows: Crankcase Heater Power per Com

I would like to get the output values of VRF performnance curves for validation purpose.

I tested with an ExampleFile VariableRefrigerantFlow_5Zone.idf (V25-2-0). The output values of the following curves are -999 throughout the year, which indicates the curves are inactive or unused.

1. Cooling Combination Ratio Correction Factor Curve
2. Piping Correction Factor for Length in Cooling Mode Curve

FYI, the Output:Variable settings are as follows.

Output:Variable,
    COOLINGCOMBRATIO,        !- Key Value
    Performance Curve Output Value ,  !- Variable Name
    Hourly;                  !- Reporting Frequency

Output:Variable,
    CoolingLengthCorrectionFactor,  !- Key Value
    Performance Curve Output Value ,  !- Variable Name
    Hourly;                  !- Reporting Frequency

For 1, it will not be used when CR is less than 1. I reduced the heat pump's Gross Rated Total Cooling Capacity by hardsizing it, but I still got -999.

For 2, I changed the performance curve coefficients, and the cooling energy use changed. So, the curve is actualy used.

I tested all types of Reporting Frequency, but in vain.

How can I get the output of the two curves?

Thanks Greg for taking the time.

I found the results of the curves in the eio file. Thank you so much!

How to get VRF Performance Curve Output Value I would like to get the output values of VRF performnance curves for valid

VAV Damper Heating Action EnergyPlus I/O Reference, AirTerminal:SingleDuct:ConstantVolume:Reheat, Damper Heating Action

Reported. https://github.com/NatLabRockies/EnergyPlus/issues/11475

Page 29 mentions the flat part where PLR exceeds 1 in Figure 8 on page 26. The vertical axis of Figure 8 is power input,

all other capacity and EIR curves were set to coef 1 = 1, Coefs 2-6 = 0. That's inappropriate. For EIRFPLR, if you

I want to model HVAC system: PAU (primary air handling unit) + AHU as shown below. One PAU is connected to multiple AHUs. The PAU supplies outdoor air to AHUs.

Can it be modelled in EnergyPlus in the first place? If yes, how can it be modelled? If no, is there any other software that can model it?

I tried some tricky modelling as follows, but in vein.

For Failed model 1, I tried to connect AirLoopHVAC:ZoneSplitter of PAU Airloop to OutdoorAir:Node of AHU1 AirLoop and AHU2 AirLoop, but I got severe error saying "Node OUTSIDE AIR INLET connects to no component" and "An outlet node in AirLoopHVAC=PAU is not connected to any zone".

For Failed model 2, I added zone 21 and zone 22 and used AirLoopHVAC:SupplyPlenum and AirLoopHVAC:ReturnPlenum instead of AirLoopHVAC:ZoneSplitter and AirLoopHVAC:ZoneMixer, but I got the same severe errors.

OutdoorAir:Mixer is essensital for AirLoopHVAC and cannot be deleted.

I don't know how to connect PAU supply air duct to AHU1 and AHU2.

Currently, I have to compromise and change the Air-side Schematic as shown below.

For Compromise model 1, one large PAU is divided into two small PAUs.

For Compromise model 2, There is only one PAU, but it supplies outdoor air to each zone directly.

In terms of energy consumption, these HVAC systems might consume almost the same energy as the original system (PAU connected to AHUs), but I want to model the original system and compare with Compromise model 1 and Compromise model 2 in order to confirm it.

A bug report.

I tried modelling optimum start control to zone VRF.

I used an ExampleFile: VariableRefrigerantFlow_5Zone.idf (V25-2-0).

Originally, AvailabilityManager:NightCycle is modelled in one of ZoneHVAC:TerminalUnit:VariableRefrigerantFlow objects: TU1 in the idf file. I replaced it with AvailabilityManager:OptimumStart. Then, EnergyPlus crashed with few clue in the err file.

The idf file is here.

Some findings:

• Crashed with other versions e.g., V25-1-0, V23-1-0, V9-4-0 and V8-9-0.
• Crashed regardless of Control Type of AvailabilityManager:OptimumStart
• Simulated successfully for ZoneHVAC:FourPipeFanCoil with another idf file. The crash seems to be specific to ZoneHVAC:TerminalUnit:VariableRefrigerantFlow.

This post is about optimum start for VRF. I wonder if @apdavis or @Julien Marrec has successfully modelled optimum start for zone VRF.

Thank you for your prompt review. The ExampleFile I had tested optimum srart for FCU is 5ZoneFanCoilDOASCool.idf. It h

EnergyPlus Crashes with Optimum Start for VRF A bug report. I tried modelling optimum start control to zone VRF. I use

5ZoneNightVent2.idf models night purge with ZoneVentilation:DesignFlowRate. That's another option. I'm wondering if Avai

5ZoneNightVent2.idf models night purge with ZoneVentilation:DesignFlowRate. That's another option. I'm wondering if Avai

How to model Night Purge Has anyone modelled night purge (night ventilation) in EnergyPlus using AvailabilityManager:Nig

Location of Preheat coil I'd like to confirm the location of a preheat coil which is required for ASHRAE PRM Baseline Sy

@Aung I followed the severe error message and changed the thickness of alminum panel from 0.002m to 0.4m. The R-value of

How can DCV and VAV be compatible in both heating and cooling? Has anyone been able to successfully implement CO2 based

Supplement: Minimum Outdoor Air Flow Rate in Controller:OutdoorAir does not actually ensure the minimum outdoor air flow

Optimum Start Control for Appendix G Baseline Does anyone know if Optimum Start Control needs to be modelled in the Base

To be precise, yes, it’s not the case for blow-through. Also, “the temperature at the setpoint node in whatever SetPoint

Central Cooling Design Supply Air Temperature in Sizing:System Central Cooling Design Supply Air Temperature in Sizing:S

As per the title. Sorry for asking about a very fundamental requirement of ASHRAE90.1 Appendix G, but I'm not 100% sure. What is the number of cooling towers for the Baseline case?

I have been modeling Tower per Chiller as shown on the left side of the schematic below. If the Baseline case has 10 chillers, it also has 10 cooling towers.

Supporting document: [ANSI/ASHRAE/IES Standard 90.1 Performance Rating Method Reference Manual] (https://www.pnnl.gov/main/publication...)

On the other hand, the original requirement of G3.1.3.11 states that the heat-rejection device shall be an axial-fan open-circuit cooling tower. It also states that each chiller shall be modeled with separate condenser-water pumps. If I interpret these requiremrnts as they are, the schematic would look like the one on the right below.

Which is correct, Tower per Chiller or only one big Tower?

The propbem of the only one big Tower is that the condenser loop shown on the right does not work in EnergyPlus. It seems that EnergyPlus does not allow to model condenser pumps immediately before or after chillers. When I modelled the schematic on the right in EnergyPlus, no warning/severe error about component connection appeared, but there was no water flow on the condenser loop. Condenser pumps and one cooling tower did not work.

SUPPLEMENT

EngineeringReference describes pump placement relus in EnergyPlus.

When will v2025 be officially released? Unfortunately, our company does not allow installation of any beta software.

Reported. https://github.com/NREL/EnergyPlus/issues/11228

ZoneHVAC:ExhaustControl does not work A bug report. I ran an ExampleFile 5ZoneAirCooledWithDOASAirLoop_ExhaustSystem.id

I think what @Yingying Tai wants to model is as follows. I also want to model the thermostat control because it is sp