System to System Damper

[asommer]

I have an EXHAUST system routed to an Energy Recovery Unit.  I also have a RETURN system to my Air Handling Unit.  I need to create a DAMPER family to go between the two systems.  I first used a damper, changed the Family Category to Mechanical Equipment.  The connected flows are correct, however I cannot get it to add to the SYSTEM to check pressure drops and size duct.  If I select it, it says it is part of both systems, but the System Browser shows it as unassigned.

If I make it an "Air Terminal" Family Category, I can add it to one system or the other.  This is a realistic setup in a lot of larger buildings, how can I get this to work?

[asommer]

Please see attached PDF for a diagram of what I am trying to accomplish.  I cannot seem to get this damper to work properly between the two systems.

[asommer]

Is nobody using systems like these?  33 views and no comments?  Hey, big brother, you on vacation?

[Jrobker]

Did you get a private message? I forgot eric.grey, same domain. I would ask him first.

[asommer]

Yeah, I got it. Thanks, Jrobker.

[rodney.page]

Would you be able to upload a sample project file highlighting the issue.

[embolisim]

I would have expected it to work as a mechanical equipment, with each connector added to the system on its own side & mapped to a flow parameter.

I haven't tried obviously.

Presumably you've tried a million different combinations of connector settings.

Please post back the answer if you get one...

[asommer]

I'll try to make a sample this evening.  I cannot send my project file.

[rodney.page]

This case is being escalated to Autodesk Product Support for further investigation.

We will keep you updated on it's progress.

[rodney.page]

According to Development you can connect one system to another, but the calculation function seems not to work very well in this condition. I personally think it is difficult to do that, because Revit doesn't know when the damper allows air to go from the return system to exaust system. The Damper is a family, but there is no way to control the air that goes through it, and the percentage of the air that goes through it. I will be lodging this as an enhancement request with Development on your behalf.

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[embolisim]

Obviously you cant connect different systems directly, but thats not what asommer is trying to achieve.

I routinely connect Return Air Systems to Outdoor Air Systems via a plenum family or FCU Ra spigot, then feed the combined flow out to the diffusers. Sometimes I use a formula SupplyAir-OutdoorAir=ReturnAir & push the value out to the Return Air Grille, if I'm using small FCU's that only have one. Once you are in the parameters dialogue its just a flow value, not a system type.
Surely it works the same with a damper family.

I havent tried this yet & am away from a Revit machine for 3 weeks (yay!).

I'd make it a mechanical equipment and NOT link the connectors, but other family types might work too.


With connectors of the right system type &  mapped to the relevant flow parameters...

For percentage of flow;

ReturnAirIn (calculated) = ExhaustAirOut*DamperMultiplier
ExhaustAirOut (preset) = <user input>
DamperMultiplier = DamperPercentOpen/100
DamperPercentOpen = <user input>

Or for fixed flow;

ReturnAirIn (calculated) = ExhaustAirOut
ExhaustAirOut (preset) = <user input>

Or visa versa.

You do need to know how much flow you want to bypass & put the value, or percentage, into the family manually.

Just thinking now, the ones I called calculated might need to be preset too.

Anyway HTH.

[asommer]

The damper is set up with the connectors not linked, and I have multiple families as a trial- one is Equipment, one is an Air Terminal, so on and so forth.  The "Equipment" allows me to attach it to the two systems, but the "Systems Browser" does not show it nor show the flow that it contributes to each system.  It works correctly when I select the downstream duct in the System's Main duct, it adds the flow from the damper to the main (but NOT in the System Browser).  If I use the damper as an Air Terminal, It displays in the System Browser properly, and adds the flow, but I can only add it to ONE System.  The flow setting should take flow out of one system and put it into the other.  I shouldn't have to formulate anything here.  I'll just have to work around this one, and put off the calcs again 'till 2013.

[asommer · Accepted solution]

I GOT IT!!!!!!!!!!  (This was far back there, too)           The damper is an Air Terminal, connectors not linked.  Return connector set to Preset, Out, and the Exhaust connector is also Preset, Out.  I wanted to specify a flow at this terminal to take air out of the Return and add it to the Exhaust, so I created a "FLOW", and associated the Exhaust connector with that flow.  Easy.  Now, the Return connector didn't take flow from the Return when it was "Preset, In", so I created another parameter "FLOWMULTI" with a formula of Flow*2.  Then, a parameter "Return Flow" = FLOWMULTI - FLOW gives me a NEGATIVE number matching the positive "FLOW".  IT WORKED!

You would think that would be the same as the Return connector set to "IN" flow direction, but that didn't work.  Now, the flow gets pulled from the Return system and added to the Exhaust system.  SYSTEM TO SYSTEM DAMPER!

Now I just have to figure out why the "System" is still "Not Well Connected".