I really need your help, I have an HVAC system problem.

[Charles.Ball]

Long story short, I have 1 AHU the feeds 2 floors, each floor has 6 supply diffusers. 5 of the diffusers are connected directly to the AHU, 1 diffuser is connected to a CAV, then to the AHU. I can't connect more than one system to the same piece of equipment, and I can't make a CAV and 5 diffusers into a system, so what do I do?

[AutoCAT95]

Hi,

Make sure if CAV System Classification (Supply, Return) is the same as other commponents you want to join in.

[RobDraw]

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@Charles.Ball wrote:

I can't connect more than one system to the same piece of equipment, and I can't make a CAV and 5 diffusers into a system, so what do I do?

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Just saying you can't do it doesn't tell us anything. Why can't you do it?

Share what you have modeled so far for more direct answers.

[Charles.Ball]

It was more a statement of fact, as in, Revit doesn't let you do it. Unless I am wrong and Revit does allow you to do it and I am messing up. 

I add the air terminal(1) to the cav(1), which is system SA 1.

I add the air terminal(2) to the cav(2), which is system SA 2. 

If I select both CAVs at the same time, the option to create a system is not available.

If I select CAV(1) I can create a system in which I select the AHU as the equipment. If I now select CAV(2) I can create a system but when I try to choose the AHU as the equipment, I cannot (it is grayed out). 

I select the 5 air terminals on the 3rd floor and create a system (SA 3) I can add the AHU as the equipment (SA 1 also has the AHU as its equipment)

I select the 5 air terminals on the 4th floor and create a system (SA 4), when I try to add the AHU as the equipment, I cannot (it is grayed out). 

I don't know why I cannot select the equipment to add it to the system, that is why I am here. 

I can't share the model, it's against company policy. 

[RobDraw · Accepted solution]

Don't create the systems or try to add to them. Just connect everything in the model and let Revit take care of the systems.

[Charles.Ball]

When I do this, I get a 0CFM Flow at my AHU in the System browser. Is this correct? All of my air terminals and CAVs are showing the correct CFM. The supply air connector on the AHU is set to "calculated". I have no flow errors or "inline equipment is end-of-line" errors. 

[RobDraw]

Of course it's not correct. Check the flow in the ducts to narrow down where the error is.

[Charles.Ball]

All of the Supply ducts read correctly. I even removed the other connector for the OA just to see if that had an effect. Could it have something to do with the parameter that the connector is associated with inside the family? Does that parameter have to be an instance parameter?

[Charles.Ball · Accepted solution]

Yep. When I changed it to an instance parameter it worked. I thought I had done that before. Good to know for the future.