TiejunWu's profile - activity

I was modeling a simple air loop in OpenStudio, in the exported EnergyPlus IDF file, the "Sizing:System" object shows that the "100% Outdoor Air in Cooling" and the "100% Outdoor Air in Heating" were automatically set to "Yes". I think this would lead to significant over sizing of the cooling and heating coils. However, I did not find a place in the OpenSutdio user interface that I can specify these two fields to "No".

I can confirm this issue has been resolved.

Designday heating load higher when I add drape to window To see how a window shade will affect the zone load, I modified

Thanks for your reply. The reported value is for winter design day. The sky clearness is set to 0, which means no solar

Designday heating load higher when I add drape to window To see how a window shade will affect the zone load, I modified

Designday heating load higher when I add drape to window To see how a window shade will affect the zone load, I modified

Designday heating load higher when I add drape to window To see how a window shade will affect the zone load, I modified

Designday heating load higher when I add drape to window To see how a window shade will affect the zone load, I modified

Just curious in this configuration, how is the outer zone floor surface represented in EnergyPlus? Its essentially a rec

Packaged rooftop energy use will include the energy needed to heat the outdoor air. The default ideal air load does not

Model a Passive Louvered Window Overhang in EnergyPlus I checked and there doesn't seem to be an EnergyPlus object for t

Model Passive Louvered Window Overhang in EnergyPlus I checked EnergyPlus and there doesn't seem to be an existing input

Model Passive Louvered Window Overhang in EnergyPlus I checked EnergyPlus and there doesn't seem to be an existing input

You can try the option "SequentialUniformPLR", this option was added to ensure that when chillers are sequentially loade

You can contact HAP helpdesk at software.systems@carrier.utc.com, they usually reply on the same day.

The Zone Heating Supply Air Temperature is for the purpose of sizing the zone heating air flow. The "Rated Outlet Air Te

I used a program based on OpenStudio SDK to generate the model.

For your case, even though the schedule type options in OS does not show a "CO2 Centration" type, you can use any schedule type that is continuous and does not have a upper limit, set the schedule value to 400 should work fine. The real issue with the OpenStudio User Interface is that you cannot assign the created schedule to the "Outdoor Carbon Dioxide Schedule Name" input box in the "Zone Air Contaminant Balance", which is under the "Simulation Settings" tab, it does not work even if you type in the schedule name.

I was just using a constant schedule of 400 ppm for the outdoor CO2 concentration.

I met the same error as this post. However, I am not using Air Flow Network Simulation. What I have is a simple 1-zone building, with one fixed window. Looks like I can get rid of this error by changing the "Zone Cooling Design Supply Air Temperature" in the "Sizing:Zone" object, if I put in any value less than 14 C, the error occurs. But I am not sure why.

I use EnergyPlus v8.5.0, x64.

I have a question about this field.

1. Can someone use a example to explain what happens to the multistage coil and multispeed fan when this field is set to "Yes" or "No"?

For example. when this field is set to "Yes", and the system load falls between stage 1 coil capacity and stage 2 coil capacity, what happens to the coil in a HVAC time step? what happens to the multispeed fan in a HVAC time step?

What happens to coil and fan when this field is set to "No"?

2 . For the coil type restrictions, does it apply to "Yes" or "No"?

Following is the screenshot of the I/O document:

In EnergyPlus documentation, I did not find any description about how the site elevation corrected standard air density is calculated. I assume it follows the method described in the ASHRAE HOF, just want to confirm.

When I put two vertically stacked spaces into one thermal zone in OpenStudio. The simulation results shows that the floor area is just half of the total floor area. Even though I have checked the "Part of Total Floor Area" in OpenStudio for each space. Looks like the internal gains (people, lights, electric equipments) were defined as per floor area, so I assume in EnergyPlus simulation they are also reduced by half. Is that what's expected?

I tried to enable CO2 concentration calculation in OpenStudio by the following setting

In which the "CO2_ConcentrationSchedule" is a schedule with value 400 ppm.

However in the generated IDF file, I did not see the "ZoneAirContaminantBalance" object. Which I suppose I should see the following object:

I was trying to run diesgnday simulation for a building with only ideal air loads turned on in OpenStudio for each thermal zone. So I set the "Do Zone Sizing Calculation" flag to "Off" position in OpenStudio GUI. But in the generated EnergyPlus IDF file, in "SimulationControl" object, the "Do Zone Sizing Calculation" flag was set to "Yes". Is this intended by the OpenStudio developers?

Yixing,

Thanks for sharing the EMS code. I copied the code and made minor modifications. The modified IDF is here . When I plot the result, I noticed that only 1 data point is below the specified minimum. Which should not be a big deal. But just curious what could have caused that outlier point?

I am trying to control a VAV air loop outdoor air flow rate to be proportional to the VAV air loop flow rate, however for the outdoor air flow rate, I want to add a minimum limit as a fraction of the design outdoor air flow rate.

See the following diagram, in which the red line shows the desired outdoor air flow as a function of the main air loop flow rate.

To achieve the proportional control behavior, in the "Controller:OutdoorAir" object, I set the "Minimum Limit Type" to "ProportionalMinimum". However I am not sure how to impose the minimum outdoor air fraction limit (the horizontal line). I have tried to set the "Minimum Outdoor Air Schedule", "Minimum Fraction of Outdoor Air Schedule" and the "Maximum Fraction of Outdoor Air Schedule". But still was not able to achieve the desired minimum outdoor air limit. Want to check whether this is actually doable in EnergyPlus.

The IDF file I used is attached here: link text

In OpenStudio when I assign multiple spaces into one thermal zone, in the exported IDF, the partition walls between these spaces gets merged into "InternalMass" in EnergyPlus. However, looks like the "SurfaceArea" of the InternalMass is only one wall area. Since EnergyPlus asks for the "total surface area exposed to the zone air" should that be two times the original wall area since both sides of the partition wall are exposed to the zone air?

I found this object in the OpenStudio SDK object list here , but I cannot find this item in the OpenStudio user interface. Does it mean I can write OpenStudio Measure to access this feature?

Actually if you just want to swap out the HVAC system, you can import the IDF file into OpenStudio user interface without going through SketchUp. You would find that the HVAC system in the original model is going to disappear and you can redefine them in openStudio. As far as comparing the OpenStudio results and the original reference building model. In addition to the missing holidays, the object "Site:GroundTemperature:BuildingSurface" in the original reference building is going be missing, which could contribute to some differences. For the 3x higher energy use from the OpenStudio, I suspect that it may result from the air loop being sized as 100% outdoor air. See this thread. If that is not the reason, you can always compare the original reference building model IDF file and the OpenStudio generated IDF file directly, which may take some time.

Mike, Thanks for the clarification. My understanding is that if a zone does not have non-HVAC system ventilation, with Ideal air system, if someone is going to use the calculated design load to size a cooling coil, the result with "ZoneVentilation:DesignFlowRate" is appropriate for use. However, if the calculated design load is used to size the zone supply air flow rate, the calculated design load without the "ZoneVentilation:DesignFlowRate" should be used.

I was importing the DOE reference building EnergyPlus model for medium office into OpenStudio and turned on the Ideal Air Loads in OpenStudio to see if the sizing result would be different between OpenStudio run and EnergyPlus run. From the results, I did see a significant difference (max difference ~2300W) in the "Calculated Design Load" for "Zone Cooling" from the html output file.

Then I checked the IDF file generated by OpenStudio and compared with the original Reference building model. I can see that OpenStudio exported IDF has defined "ZoneVentilation:DesignFlowRate" objects for each zone.

The original EnergyPlus model has only the "DesignSpecification:OutdoorAir" objects for each zone. I tried to copy and paste these "ZoneVentilation:DesignFlowRate" objects from the OpenStudio exported IDF file to the original IDF file and ran the simulation again, it did eliminate most of the difference between the zone sizing load.

My questions are:

1. Is there a way to set OpenStudio model to not generate the "ZoneVentilation:DesignFlowRate" objects since they are causing the differences?

2. Even when I matched the input files by adding the "ZoneVentilation:DesignFlowRate" objects to the original EnergyPlus model, there is still small difference in the zone load(~50 Watts). Since they were results from the same version of EnergyPlus engine, What could be causing the differences?

C:\fakepath\OriginalEnergyPlusOutput.PNG

C:\fakepath\OpenStudioOutput.PNG

C:\fakepath\ModifiedEnergyPlusOutput(Added ZoneVentilationDesignFlowRate Objects).PNG