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Thermal Zones in Series

asked 2020-03-15 15:45:26 -0500

updated 2020-03-15 21:13:58 -0500

OpenStudio allows input of thermal zones in series on the demand side of an air loop. Does this actually work to transfer air between the zones, or is this a flaw in the programming?: image description

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answered 2020-03-16 11:28:30 -0500

updated 2020-03-16 11:30:25 -0500

This appears to be a flaw in OpenStudio. If you try to assign a second thermal zone "downstream" after a thermal zone in one of the horizontal lines on the demand side, OpenStudio will do one of two things.

First, the correct thing it should do -- give a warning that this isn't allowed and prevent the user from making that mistake (see below).

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Second, the wrong thing it does in your case -- connect the second thermal zone downstream (see below).

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If you eventually try to simulate with an HVAC system like this, you will get a severe error that stops the simulation (see below).

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I haven't done enough testing to know when OpenStudio works correctly vs. incorrectly, but this may be worth reporting as a bug/issue on their Github repository. It does not appear that a similar issue already exists.

I believe the only way that you can have two zones in series on the demand side of an air loop is if one of them is a plenum zone. Two conditioned zones cannot be in series with each other for OpenStudio/EnergyPlus.

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I investigated the issue and confirmed it's still present today. Added a bug as NREL/OpenStudio#3917

Julien Marrec gravatar image Julien Marrec  ( 2020-03-16 17:33:22 -0500 )edit

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Asked: 2020-03-15 15:45:26 -0500

Seen: 120 times

Last updated: Mar 16 '20