Knowledgebase: HVAC > Air Loops
When I use an Earthtube with an AirFlowNetwork, I get a "Orphan Object" warning
Posted by - NA -, Last modified by Michael J. Witte on 28 November 2017 07:19 PM
Currently, Earthtube and AirFlowNetworks do not work together. If both objects co-exist, the AirflowNetwork mode supersedes the Earthtube mode at two
control choices. Since this causes the Earthtube objects to not be used, the "orphan" warning appears.

There are four control choices in the second field of the AirflowNetwork Simulation object:

MULTIZONE WITH DISTRIBUTION
MULTIZONE WITHOUT DISTRIBUTION
MULTIZONE WITH DISTRIBUTION ONLY DURING FAN OPERATION
NO MULTIZONE OR DISTRIBUTION

When the first two choices are selected, the AirflowNetwork model takes over airflow calculation. The earthtube objects are not used in the airflow
calculation, causing the "orphan" warning. The example file, AirflowNetwork_Multizone_SmallOffice.idf, uses the first choice. When the second choice is used, the AirflowNetwork model is only used during HVAC operation time. During system off time, the earthtube model is used to calculate airflows. Thus, no "orphan" warning will be given, but the earthtube may be being used less than expected. The example file, AirflowNetwork_Simple_House.idf, uses the third choice.
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