IES-VE User Forum

Hi,

I have few questions about Sizing Runs in PRM Navigator because it's not clear to me how it works or in other words, how I should work with it:

1) I must always run the Sizing Runs for my Proposed Building before running sizing for the Baseline? Even though I previously made settings on my Prpsd HVAC network and there is possibility that my settings will be gone? Or not? It doesn't make me any sense, but it seems to me that without creating data spreadsheets for Prpsd I'm not able to get any results for Bsln (in reports for Bsln there is nothing to see) and in components of HVAC network in Bsln there are no changes made.

2) It happened to me that when I ran Sizing Run from navigator no error occurred in HVAC network on equipment and plant, but when I ran the very same HVAC network from Appache HVAC by "system equipment and plant sizing" button it gave me 2 error messages and simulation stopped. In first case no results were given of course and I didn't know why until I ran the sizing from AppHVAC and found out. Has anyone similar experiences and tell me why sizing runs navigator did not detect any errors in HVAC network?

3) Finally I got the report where peak load for heating and cooling were calculated, but further in report the cooling coils in every room has no load even though cooling peak load was claculated. No problem with heating coils. I noticed the same in navigator User's guide (picture on page 70). It is OK? In data spreadsheets cooling load for each room is calculated, but no total cooling load is quantified. I really don't understand.

I would appreciate any suggestions what steps and in what order I have to make for correct results and so on, mainly the first question is critical for me, because I'm little bit confused by now and I already spent too many time with trying and searching on my own. I think the PRM Navigator is very useful and handy utility, I had no problems with it until now.

Thanks in advance for any advice!

And I'm sorry for my English

Martin

Let me walk through the sizing steps in the navigator before answer your specific questions as it will provide good background and be useful to other forum participants:

In the “HVAC Systems” second of the navigator, you create ApHVAC systems for your Baseline & Proposed buildings. When you click on the “System Parameters” link, the spreadsheets for the systems you created are generated. At this time, the Baseline HVAC file is copied for each of the 3 rotations and the corresponding spreadsheets are created as well. At this stage, the spreadsheets are not populated.

Further down the navigator, you “Generate the baseline model”. This step creates the Baseline building by applying the PRM rules to your Proposed building.

Once the Baseline building is generated, you move on to the sizing runs. First up is “Room Load Calculations”. This sizing step determines the load in each room for the Proposed building, Baseline building, and Baseline building rotations (assuming you check the boxes to perform them all). Room loads are calculated using the ASHRAE Heat Balance Method and the results of those calculations populate the spreadsheets created above.

The “Access Loads Data Spreadsheets” link in the navigator connects you to the folder on your computer where the spreadsheets are saved. You can open them up to make changes as needed. You may not need to make any changes, depending on your building, design stage, etc, but a review of the data here, including the 62.1 OA Calculations, is encouraged.

Once your spreadsheet changes (if any) are finalized, you’re ready to “Assign Room Sizing Data”. This step copies data from the spreadsheets into the corresponding ApHVAC networks. This copy/paste communication only flows one direction and only happens when you perform this step. That is, if you make changes to the ApHVAC network, they do not write backwards to the spreadsheet. If you make changes the ApHVAC network, then perform this step again, the spreadsheet may overwrite those changes. If you make changes to the spreadsheet and don’t perform this step, the changes are never made in the ApHVAC network.

“System Load Calculations” looks at the information in your ApHVAC files and sizes the equipment and plant accordingly.

All of the above steps are the same in the navigator as within ApHVAC. The only reason you need to use the navigator (outside of preference/convenience) is to access the Baseline building. If you open the Baseline HVAC file in ApHVAC and perform the sizing steps there, the file will size using the Proposed building. To size the Baseline HVAC file to the Baseline building, you must perform the sizing in the navigator.

Answering your questions more specifically:

1) No, you do not have to size the Proposed building HVAC file to size the Baseline building HVAC file. Simply uncheck the “Proposed” option when prompted and only the Baseline & rotations will run.

If you are not sizing the Proposed, no changes will be made to your Proposed file. You can certainly do a “Save As” on your Proposed HVAC file and give it a new name as a backup, just in case you accidentally forget to uncheck the box.

What reports are you looking at that you see no Baseline data? What changes are you expecting to see in the HVAC Component results in VistaPro that are not appearing?

2) If there is an error in your ApHVAC file, you should see that error whether you perform the System Sizing in the navigator or within ApHVAC. It is possible you are sizing the Baseline HVAC file directly in ApHVAC? This would be the only instance where the two processes would differ (see above explanation). If you are not, I encourage you to send this model to support@iesve.com so they can investigate.

What errors are you receiving? Are the specific to the network (negative flow, flow overspecified, mismatched control variable, etc) or something else related to sizing?

3) Looking at page 70 of the IES VE PRM Navigator User Guide, I see a System Sizing report for a System type 7. A system 7 is a VAV AHU with terminal units. At the top, I can see the coil sizes for the AHU cooling & heating coils. At the bottom, I see a list of “Rooms Served by System”. In this table there is only heating coil data and no cooling coil data, as I would expect. At the room level, there are only terminal units with reheat. The terminal units do not have cooling coils, thus there is no data here. All of the cooling is addressed the AHU level.

Thanks,
Megan

Thank you for your quick response Megan.

Your explanation is very clear and I just confirmed to myself what I thought how it all should be.

My problem could be in one thing: the navigator did not discover error in HVAC scheme when performing the "system load calc", but maybe "discover" is not correct word, so let's say that it did not gave me any error message and then I didn't know that the system load calculation wasn't completed. Even updating was performed without any warning. I found out only when I was desperate and accidentally performed the calc from ApHVAC. It detected negative flow on EA branch and it was caused by wrong assigned schedules. So I fixed it but no results appeared in Bsln sizing report anyway - it was blank, components in HVAC scheme (not in Vista) as a chillers, boilers, coils had no green autosized values and so on. Now I think it was caused maybe by previous imperfect calc and something like that... This morning after reading your post I tried to perform calc from beggining with corrected HVAC scheme, without any previous data spreadsheets, any previously calculated results etc., and it seems as everything is all right. So I will see in next project.

Question is why the navigator did not alert me, or did not gave me an error message. Anyway I know by now that I have to check properly any HVAC scheme before start autosizing.

Megan, I didn't expect changes on the HVAC component to see in Vista. But directly on the plant and components (coils and fans) related to the HVAC scheme after autiosizing and updating data. There was nothing autosized at all. Certainly because of corrupted calculation what was not known for me...

Regarding to my question No.3 - you are absolutely right and it's absolutely clear to me. I didn't realise it because of my desperation My apologies.

Thank you once again Megan.

Martin

Martin,

Glad to hear things are working well for you now! I'm not certain why you wouldn't have received the error when performing the sizing in the navigator steps, but I will keep an eye out for other customers with the same problem in case it's an issue with the software.

Thanks,
Megan