LEED refers to this as a District Energy System (DES). You should begin by reading the DES Guidance from USGBC.
Once you have decided which option from the guidelines you will use, follow these instructions:
Option 1 – This approach requires you to treat the plant chilled water and hot water as purchased commodities thus removing any efficiency associated with the central plant from the model. You will model your HVAC systems as normal and input whatever central plant is appropriate for the chillers, boilers, towers and pumps (you will be discarding all of these numbers so it is not important). When running the calculations, under the Calculation Options, check the box for CSV reporting (covered in another FAQ) and uncheck Delete Temporary Files. Now you can run the calculations.
After the calculations are complete, you will open the CSV file in Excel and you will find hourly data for the various end uses (note the units of each column). The columns for Heating, Cooling, Heat Rejection and Pumps* can be discarded. On the far right you will find columns for Chilled Water and Hot Water demand for the building. These are the purchased commodities you will use to follow the DES guidelines. Any columns that represent normal building usage (lighting, fans, receptacle) should get multiplied times the virtual rate for Gas or Electricity (found on the EAC1 report). The Chilled Water and Hot Water use is multiplied times the rates given in the DES Guidance and you will have a spreadsheet that documents total energy cost for your building.
In some cases, the Baseline building may not be a chilled water system so EnergyPro will configure a baseline with DX equipment. In this case, you can force EnergyPro to use a chilled water system by changing one of the Zones to a Floor Number of 5 and it will structure the baseline as chilled water.
Option 2 – With this option you are allowed to model the actual efficiencies of the central plant in EnergyPro only you will scale the actual equipment according to the load served. Be sure you understand the documentation requirements given in the DES Guidance document from USGBC since this approach requires supporting data on the efficiencies you are using.
*If you have only pumps as part of the CUP, discard the pump number from the calculation since it is part of the purchased commodity. However, if you have local pumps at the building, model those and include them in the building energy usage numbers.
They are just warnings, if you feel your inputs are set properly then it is fine to ignore them. EnergyPro sets standards for these inputs and gives you a warning if anything is more than 30% outside of that range.
Note that this section applies to EnergyPro V8 or above, and non-Title 24 applications of VRF systems. For Title 24 applications, see this FAQ.
The VRF models are located in the sample files, located in the example files section of this site. You will need to export the systems from the sample file into the file you are working with. Begin by opening your project, and then open one of the sample files with the Manufacturer name of the models you wish. Navigate into the Central System library in the sample file by clicking on the bottom left button “Libraries” and then in the pane above, select “Central”. A list of models will appear on the right for you to select. You can select multiple systems by clicking on one system, then holding down the shift key and selecting another system. Once you have selected all of the systems you want to export, select the export button on the top of the window. Select your project from the window that appears (you may need to scroll to the bottom of the window) and hit ‘OK’. The systems you had highlighted will now be available in your project.
Repeat this procedure by selecting the “Zonal” library and exporting all of the indoor units.
Since a single zone system only has one thermostat, the first zone listed in the tree is the control zone, the other zones just get whatever the control zone calls for. This should be modeled as one system for each zone.
Below is a list of tabs in which you need to enter information for a non-residential LEED calculation. You will not need to enter every available input in each tab.
Project Design Data, Project Title, Designer, Lighting Designer (if lighting is part of your scope), Mechanical Designer (if Mechanical is part of your scope), Outdoor (if outdoor lighting is in your scope), Utility
Heating Hot Water (if you have a boiler for space heating which is separate from the domestic hot water heater), Chiller Water (if you have a built up HVAC system with a chiller) Hydronic (if you have a ground coupled system) Domestic Hot Water (unless DHW is not in the scope), Renewables, Exceptional
General, Lighting, Mechanical (if you have zonal mechanical boxes or wish to adjust the ventilation), schedules
General, Infiltration, Occupant, Receptacle/Process, exhaust fan, lighting (if you are taking task or daylighting credits).
Within the Room icon, you will enter building assemblies such as Roofs, Walls and floors by right clicking on the room icon and selecting Add …
The SS-Z documentation is reporting the VRF system performance only. This is how DOE-2 reports the outside operation and system performance of VRF systems.
The PS-D reports the Total Plant Loads for the entire project as compared to the reporting of the VRF system only as found on the SS-Z report.
Most utility rates are either tiered (residential) or time of use (commercial). As a result, different charges will occur depending upon when your building is using energy, as well as how much it uses. Energy usage in the higher tiers tends to be more expensive, as is the energy usage during peak periods. Unless the baseline building and your building have exactly the same load profiles, the virtual rate is going to vary. In addition, many rates carry a base monthly meter charge that can be substantial and is included in the overall rate.
At the Top level of the Building Tree, Utility Tab, you will find selections for all of the available DOE-2 reports. Select them as necessary but be careful, if you select too many, DOE-2 will not run since it is more reports than it can handle.
Now, go into the Calculation Options, select your desired calculation and on the right side of the screen, deselect “Delete Temporary files”
See Screen Shot below.
Once you do this, rerun the calculations so the reports will be generated
Now, go to the Report selections in EnergyPro and choose the Proposed (or Standard) DOE-2 report selections in the list of reports and hit print.
Also you can go to My Documents\EnergyPro 7\Results\ProjectName and you will see the files with the .SIM extension, these will contain the same reports.
If a file is crashing, check the DOE file to see why. The DOE file error message may be a bit confusing, but will give you an idea of why the file is crashing.
To check the DOE file, uncheck the ‘delete temporary files after calculation is complete’ button in the calculation you are running.
Then go to the results folder located at My Documents/EnergyPro 6/Results. A folder with your projects name will contain a file called ‘proposed.bdl’.
Search proposed.bdl for the word ‘Error’. There will be many results, you are looking for the word ERROR with many stars across the page (ERROR*********************************). Right after the string of stars there will be a message that states why the file is crashing.
Dates not is sequence means that the utility weekly schedule, or a zonal schedule has dates out of order. Schedules need to be in chronological order.
If you are getting all zeroes in your results your file is crashing or you have everything set as existing. Your file could be crashing for a number of reasons. A very common reason is that the interior surfaces are not inputted correctly. Interior surfaces should be entered in conditioned spaces, and need to be set adjacent to an unconditioned space.
If you have a wall with negative area, your file will crash. A negative area happens when you have a glazing area that is larger than the wall it is in. For example, if you have a 60 square foot wall and a total of 70 square foot of glazing in the wall, the file will crash. The same goes for roofs and skylights.
If you have entered Week Periods in the utility rate incorrectly, your file will crash. Week Periods need to be is chronological order, starting on Jan. 1st and ending Dec. 31st. The month and day is the ending day for that period. So the top line starts on Jan. 1st and ends on the date entered. The next line down starts on the day after the previous period ends. The last period needs to end on Dec. 31st. See the screenshot below.
If you have selected many DOE-2 Reports to be run your file might crash. Deselect all of the DOE-2 reports then select only the reports you need.
Interior surfaces are surfaces between two spaces and can be either walls, ceilings or floors. Note that interior walls can also contain doors. If you have an interior window, treat it as an interior door in an interior wall. Insert an interior surface in the room and set it adjacent to the other room. If you do not set it adjacent to another room, or you set it adjacent to itself, it is treated as adiabatic.
In New Construction Homes, Title 24 recognizes (and generally requires in order to comply) your inputs for PV, however in no case does the credit get recognized in additions and alterations.
In Nonresidential occupancies, Title 24 does not allow you to take credit towards compliance. In the remaining performance calculations, EnergyPro will assign full benefit for the PV production.
The top occupancy box titled ‘Occupancy’ is for general use. The lower box titled ’90.1 Ltg Occupancy’ is for lighting calculations based on ASHRAE 90.1. If you are not doing a an ASHRAE 90.1 calculation then you do not need to make any selection in the lower box.
You probably have a wall, roof or floor selected that has a name which does not match the actual R value of the assembly. See screenshot below. You can name a wall anything you want. The actual R value that will be used in the calculation and will show up on the report is highlighted in the screenshot. You will need to select a different assembly with the proper R value.