A while ago, I posted a message about fixing a piping system to make it "well connected" and thereby able to generate a piping pressure loss report. It seemed to be liked by quite a few people (98 views, 4 kudos), and hopefully it worked and was helpful for them. You can find it here:
http://forums.autodesk.com/t5/revit-mep/how-to-fix-your-piping-system/m-p/5297939
Well, as I progress through this large project at work, I am learning more and more so I thought I would write another How To for ductwork. So here it is!
HOW TO MAKE A "WELL CONNECTED" DUCT SYSTEM (on the Supply side):
Making sure all of these connectors are set appropriately will allow the airflow value assigned at the air terminal to propogate back to the AHU properly.
2. Make sure all duct is complete and fully connected, this means there will be a non-zero flow value in all duct
If these two steps are completed, you will have a "well connected" system. Here's the kicker...Revit may not realize it and still give you problems. The "check duct system" tool may still give you errors. I think this is a fault in the Revit programming, flow information seems to get "stuck".
TO FIX THIS (ONCE THE ABOVE STEPS ARE COMPLETED ONLY!!):
Ok so you made it this far, now you have two choices. You can either choose an air terminal or VAV to create your new system. If you choose the air terminal, I have noticed Revit will sit there and "think" in the background for a suuuppppppeeerrr looooonnnnggg time (approximately 8 min) before it will add the single air terminal you selected.
OR
You can select the VAV, create a new system, and it will still take a looooonnnnggg time (approximately 8 min) to add the VAV to the system, but it will also add every other VAV at the same time. I prefer this method because it will literally save you hours. Once every VAV has been added to the system, now start adding the air terminals they are connected to and you will see that it goes quickly. Total time to add every VAV and air terminal and AHU to the system should be approximately 10 min (adding the very first VAV is what takes the most time).
Now I know you are thinking this sounds crazy, and youre right...it is. Nonetheless, I have found it necessary to do it this way if I want to be able to generate a pressure loss report for my Multi VAV systems. For some reason these steps seem to flush the system and cause the proper propigation of flow data throughout the system, and this will fix the errors and create a "well connected" ductsystem.
There you have it! This is the process I use, and it helps me get all my systems set up for the pressure loss reports. Now go forth and complete your systems!
Post if you have any questions or suggestions! I will be checking to see if anyone has any questions.
Sincerely,
Wils02
I forgot to mention once you select the VAV to start the new system, be sure to select the outlet connector to "create the duct system" from.
Very nice post. I've worked with mostly ductwork myself for the past 2 years or so and you are right about the connectors. The systems I model are mainly Air Handlers connected directly to terminals. The Air Handlers are set to In/Out (SA/RA), and calculated, terminals to Preset (and reverse In/Out).
I have also notice quite a few odd things with the systems. I once had a system not working, but then I deleted an elbow down to a terminal and it worked! Explain that one to me. lol I've used similar methos to your deleting system to fix systems quite a few times. To save the loading time you could try to disconnect 1 terminal from the system, then create the system with that terminal, then reconnect it. It's a bit more work but I haven't had the issues with loading like you mentioned.
I would really like it if they added a button or feature that you could force Revit to re-examine the system. Certain things seem to make it stop working, while others are ignored and don't update it.
Tell me about it! I haven't looked into Revit 2015 yet, but hopefully they have added/will add a feature to do a better job debugging. It would help tremendously and alleviate a lot of stress. It sucks when you get everything connected and Revit will still not recognize it as a "well connected" system. Frustrating beyond belief.
For my particular project, the building is about 6 stories with 17 AHU and hundreds of VAVs and my method seems to be working. After thinking about it, it probably takes me soo long because of the size of my systems, but as a programmer myself I can't see why it would take so long to simply add another piece of equipment to a system. I have a feeling there are some behind-the-scene calculations going on that are slowing the process down. It would also be great if you could completely turn these off. I am aware of turning calculations off for the system, but it doesn't seem to help. Thats why I think something else is going on, but I don't know this for sure.
Anyway, glad you liked it! Good luck with your stuff.
wils02
To update my post about fixing the duct system, I have a tip that will eliminate the time it takes to add a piece of equipment to the system.
Just to re outline the steps below:
This next step is where the time savings come in; yesterday I posted that it would take about 8 min to add a single VAV to the system. This is true, but it is mostly due to the size of my ductwork and building. However, if you find yourself in the same situation here is the workaround.
Following these steps and assuming you have followed the other previous steps before, you will have a "well connected" system in the eyes of Revit. You are now able to generate your pressure loss report!
Have fun
Outstanding, but the problem here not in the settings, but inherently in AHU never had a System classifications, all the times it gives: Undefined.Power which i don't know what does it mean, but VAV box always has a system classification. who did this?
Hello,
This is awesome! Thanks for taking the time to make this!
After following your procedure. I continue to have this issue pop up:
I have one correction or hint: use "global" as system type whenever possible. A VAV terminal device also can be used to control exhaust flow. Terminals like registers or diffusers should be the only items deciding what type of system it is. Everything else (like fans, or duct accessories) should just be agnostic to that.
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