Carlos Vazquez's profile - activity

I am a Trace 700 user. I am making test models while learning Energyplus. I am establishing a workflow turning on Ideal Air Loads from the Openstudio application and make an initial simulation to test geometry. After the initial simulation, in the HVAC Sizing Summary Report I am getting cooling loads about 1/3 lower from the ones calculated with Trace 700 for the same case. However, in another simulation after defining air loops and plants in Openstudio, the sizes in the Equipment Summary Report are in line with the load calculations in Trace 700 for the same case. However, in Energyplus the loads from the HVAC Sizing Summary Report are still 1/3 from the sizes in the Equipment Summary Report. I will appreciate to know why this happens! Thank you.

HVAC Sizing Summary.JPG Equipment Summary Report.JPG

There is one video showing how to model plenums in openstudio. However, is there a way to just specify ceiling heights in openstudio?

I was looking at the idf editor in energy plus and is possible to specify a ceiling height per zone. Also the manual says that ceiling height can be "heuristically calculated" in energyplus. Can somebody give me a hint or clarify for me how this works?

Thank you.

Thank you for your answers. The error message I'm getting is: Starting Simulation. EnergyPlus Starting EnergyPlus, Vers

EnergyPlus Measure Set Output Table to IP Units I have installed in my computer OpenStudio 2.4. I have always used the E

Report: System Summary DCV using Controller: Mechanical Ventilation Recently I made a model using energyplus version 8.8

I don´t use design builder. But it works with energyplus engine. And within energyplus you can model a single pump and m

For modeling window films, you first have to determine what´s the effect in the U value and Solar Heat Gain Coefficient.

I have a similar situation with a model. My opinion is that VRP is for design for a one time critical scenario. But during operation, unless you have DCV, air loops in a VAV system work based on demand from the VAV terminals. Setting VRP for a year simulation results in instances were demand from VAV terminals is low, and your VRP OA calculation is close/equal to the primary VAV terminal airflow demand, lowering the ventilation efficiency Ev below 0.5. I suggest to lock the maximum OA air to a fixed number and lock the minimum airflow fractions in VAV terminals. Min Zp is not available in EP.

I suggest that you try using sketchup 2014 with the current version of legacy openstudio (v1.0.14). There a bug of the plug-in when used with sketchup 2015 and 2016 related to unneccesary duplication of surfaces. I would have to verify again the issue to give you a better explanation. But so far, I don´t think this issue has been solved.

Hi. All the data that I have from commercial manufacturers related to chiller performance with two compressors reflects the performance of the unit as a whole. My opinion is that you have two options:

1. Look for the manufacturer data to check if you can build energy consumption, efficiency and capacity curves which reflects the performance of the chiller as a single unit with two compressors.
2. Model two chillers in series with curves for each one. Curves can be equal or different, depending on manufacturer data.

I have been doing troubleshooting for a model I´m working and has the same issue. I started building a chilled water loop within the openstudio GUI. So far, within the openstudio GUI, I have not found a solution. My situation analysis is that pump operation (whether if it´s on or off) is dependent of loop demand, and loop demand is not necessarily related to the operation of other cooling or heating equipment within the loop. Even though I have selected intermittent pump operation, undesirable heat is still being built-up within the loop.

Out of openstudio GUI within energyplus are more options to do something about it, and I added an availability manager to stop the loop when it reaches to an undesirable temperature. The object is AvailabilityManager:HighTemperatureTurnOff.

Another option is to use a measure "Enable Detailed Output for Each Node in a Loop" within OpenStudio in the Reporting/Troubleshooting tab. You can run the simulation in a shorter time period before it fails with this measure. Then you can verify the temperature patterns and tendencies for every loop that you want. That way maybe you can figure out better what is the cause of making the simulation fail.

Thank you for your answers folks. I will work with it and will let you know the result.

I need a hint to write a measure to duplicate an AirLoopHVAC already made within openstudio. I will appreciate any help.

Then take note of the subsurface description. Close your model within sketch-up. Open the *.osm file in a text editor. And lookup for the orphan subsurface within the model. There might be thousands of lines so you have to be careful in what you delete. Find the subsurface and delete it. Save the file within your text editor, close it, and re-open it again in the sketchup plug-in.

This is what is called in openstudio as an "orphan subsurface". It is not shown in sketchup but it is in your *.osm file. Within the openstudio plugin in sketchup, go to Extensions; OpenStudio User Scripts; Alter or Add Model Elements; Remove OrphanSubsurfaces. The program will give you a message confirming that a subsurface has been removed. Save and close your model. When you re-open it again, the error message will not appear again. Let me know if it works. Another way to do it is to open your *.osm file in a text editor and delete the subsurface directly from your model script.

There is also a measure within openstudio to "Remove Orphan Objects and Unused Resources"

You can also use this spreadsheet from the energyplus support website. Just copy ans paste the link in your browser: energyplus.helpserve.com/Knowledgebase/Article/GetAttachment/135/5844

Looking at the images attached, I agree that the surface match is correct. Surface matching is more related to the boundary condition of every surface within the spaces selected.

I tried the EnergyManagementSystem:Sensor object but was not able to get the pump linked to the chiller start/stop sequence. If the sensor and the actuator are both inside the chilled water loop it does not work. At least the sensor has to be outside the chilled water loop.

The chiller on/off sequence is controlled by the plant operation scheme and the loop availability manager. The pump is controlled by the loop availability manager. So far what still continues to be working better for me is to setup the AvailabilityManager:LowTemperatureTurnOff object to turn off the chilled water loop with low outdoor air temperature.

In EnergyPlus it is a recommended practice for any loop to have a bypass in both supply and demand side. Both will be more active during your simulation when having a minimum flow setup through the loop. For a variable flow primary-only loop, the bypass in the demand side will be more active. The one in the supply side might be active in any instance that both chillers are off with the pump active or when both chillers are on and unable to satisfy the load.

I have not tried that. But I don´t see other options. I will take a look at it. Thank you!

I have been looking for a way to attach the pump operation in a primary-only chilled water loop to the chiller on-off schedule in EnergyPlus. Even when I have chosen an intermittent operation for the pump, when I set a non-zero minimum flow for it, the pump starts whenever the loop is available even when the chiller is off.

I have tried other ways to turn off the pump, like setting up the AvailabilityManager:LowTemperatureTurnOff object. It works better to control when the pump starts and turns off, but still can not attach the pump operation to the chiller.

Is there is anyway to do this with a non-zero minimum flow?

I have not done it in series but in parallel. But I think it is possible. You have to make sure that you have a bypass in both supply side and demand side of the chilled water plant loop. Do not use the common pipe in the plantloop object. Place setpoint managers for both chillers. Setup chillers operation mode as "leaving set point modulated". And the most difficult thing for me, which I have been looking how to set it up, this kind of setup requires to maintain a minimum flow through the loop. You can still model it with 0 minimum flow at the pump, but is not how it works in reality. If you set the primary pump with a non-zero minimum flow, you have to figure out a plantloop schedule for the chilled water loop to turn on the chiller and pumps when necessary. This is the way I would do it...VPF Air Cooled Series.JPG

I have not been able to login to www.energyplus.net. This is the new way to login to openstudio.net. Every time I try to login a have to reset the password. Does anybody know if there is an unsolved issue with this website?

Sketchup 2015 has been released by Trimble. I have been using the 2014 version with the Openstudio 1.5 plug-in. I was able to install the Legacy Openstudio 1.11 plug-in to the 2015 version but not the Openstudio 1.5. Looks like we have to wait until NREL releases an Openstudio version compatible with Sketchup 2015 version. Does anybody has updated status of this or know a way to install the Openstudio 1.5 plug-in to make it work with Sketchup 2015?

Thank you!

Thank you for the clarification. I revised the manual again and the objects in my idf editor. For my case I realized that I have to use the CoilSystem:CoolingWater:HeatExchangerAssisted object together with another object HeatExchanger:AirtoAirSensibleAndLatent. For heat pipes in series with a cooling coil then I have to enter user inputs of effectiveness for sensible heat transfer only.

I am going to use series heat pipes for cooling coils in a model that I´m doing. Energyplus has an object called CoilSystem:CoolingWater:HeatExchangerAssisted to do this. I would like to know what is the average sensible heat transfer effectiveness in energyplus. I know that typical sensible heat transfer effectiveness for this kind of application is 32%. But I did not find a specific value in the engineering reference manual. I will appreciate your help. Thank you.

Hi! I need help to interpret the results that I am getting of a model I´m doing in openstudio. This is a chilled water secondary plant loop diagram. The supply side is a fluid to fluid heat exchanger and the demand side are the different cooling coils located in a multi-story office building. The primary loop is a typical chilled water primary loop with chillers and pumps (not shown in diagram). The plant sizing result for the primary chiller water loop is 1,366 tons, which is an expected result for me. The plant sizing for the secondary chilled water loop coincides with the primary in terms of design water flows for both supply and demand side (both have the same design temperature difference). But, for the heat exchanger, the sizing results are different: 1,590 tons if I choose an ideal heat exchanger type (16.3% over the primary plant size); and 735 tons if I choose a counterflow heat exchanger type (53.8% of the primary plant size). I have been reading energyplus engineering reference and Input/Ouput manuals to see if I find an explanation about why I am getting these results but so far I have not. Any help will be appreciated. Thank you!