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Error in Fresh Air Handling Unit

asked 2017-01-30 00:17:36 -0500

updated 2017-05-06 08:28:38 -0500

After assigning 32 Fan Coil Units and 3 Fresh Air Handling Units with COPs, simulation is giving error for FAHUs. It says:

  1. Too many zone mixers in Return Air Path=FAHU1 DEMAND SIDE RETURN PATH
  2. Too many zone mixers in Return Air Path=FAHU2 DEMAND SIDE RETURN PATH
  3. Too many zone mixers in Return Air Path=FAHU3 DEMAND SIDE RETURN PATH
  4. Return air Path(s) did not pass integrity testing

What is the solution to this? Because 8 zones are assigned to FAHU1, 8 to FAHU2 and 12 to FAHU3.

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I suspect you have (wrongly) more than one mixer on the demand side of your airloopHVACs, but without seeing the related portion of your IDF, there's hardly a way to help.

Julien Marrec's avatar Julien Marrec  ( 2017-01-30 06:59:01 -0500 )edit

What do you mean by mixers? You mean the exhaust air fan?


Adam Hilton's avatar Adam Hilton  ( 2017-01-30 08:14:23 -0500 )edit

Where is it in FAHU visually?


I mean the AirLoopHVAC:ZoneMixer like @adhilton said. Again, without seeing the IDF file (the IDF generated by design builder, not the design builder file, I don't have a license myself), hard to help. Maybe a designbuilder user could help with the DB file though.

Julien Marrec's avatar Julien Marrec  ( 2017-01-30 08:28:10 -0500 )edit

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answered 2017-02-12 00:21:46 -0500

@Julien Marrec @adhilton

In design builder, when we want to connect more than 2 components to a single Fresh Air Handling Unit there is a need to connect all components to FAHU through same mixer / splitter. Multiple mixers / splitters cause severe errors in simulation. Whenever a component is added the mixer / splitter branch automatically updates to increase in number of connections making more connectors available. See following images.!Ase9DtM9ZxGyjFqFs...

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answered 2017-01-31 01:12:35 -0500

Dave's avatar

DesignBuilder customers should submit this sort of question via a support ticket to the Help Desk...they are there to help. Look on the DB website under the Support options.

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Asked: 2017-01-30 00:17:36 -0500

Seen: 321 times

Last updated: Feb 12 '17