Principal vs. Non-principal multiplex

The Principal multiplex must be designated whenever there is a secondary, non-principal, multiplex within the same system frame. The System Parameters dialog will be coupled only to the zone layers, components, and controllers in the Principal multiplex.

The inclusion of secondary, non-principal, multiplex within the same system frame is not permitted for single-zone (system types 03 and 04) or packaged terminal units (system types 01 and 02) which are not coupled to a DOAS (as is system types 09j and 09k).

The inclusion of secondary, non-principal, multiplex within the same system frame should be necessary only when there are multiple zones that must be included on the same airside network either before or after, rather than in parallel to, the main set of zones on the system. The network below provides an example of this.

Non-principal multiplexes will be highlighted in blue, similar to non-principal rooms. For a legacy system having more than one multiplex within the system frame, the multiplex with the greatest number of layers will automatically be set as the principal multiplex when the system is first loaded, and thus upgraded.

The multiplex dialog has a new ‘Principal multiplex’ checkbox that is visible only if the system contains more than one multiplex. This is forced ticked and grayed out for the current or default principal multiplex, and is enabled and unticked for any non-principal multiplex. These checkboxes function as radio buttons in that only one multiplex can be designated as the Principal multiplex.
When checking this box for a currently non-principal multiplex, the following warning message will be displayed on clicking OK in the dialog:

The same message is also displayed if the principal multiplex is deleted, de-multiplexed, or moved out from the system.

System links set for components and controllers in a non-principal multiplex won’t be coupled to of affect the parameters in the System Parameters dialog, nor will these links assign any data to these components or controllers when you click either of the Assign buttons in System Parameters dialog.
As the normal behavior of assigning data from System Parameters UI to the component or controller being edited when a system link is first selected would be inappropriate, the system link drop-down selector and re-apply button are hidden for components and controllers in a non-principal multiplex.
Any single-multiplex legacy system of type 03 or 04 will have its multiplex resized automatically to contain all the components and controllers first time it is loaded in VE2016, thus automatically converting it to be correctly recognized by the System Parameters UI with ‘Single-zone systems’ displayed the ‘Configuration’ field. Any systems of this type containing two or more multiplexes, which is not permissible, will not be upgraded. Instead, the following warning message will be presented to the user:

‘ One or more of the airside networks in this ApacheHVAC file cannot be upgraded as required for use with the ISM System Parameters user interface. These are airside system networks of type 03 or 04, which are meant to be ‘packaged single-zone’ systems. For this system configuration, the upgrade requires that there is not more than one multiplex within the system frame. For single-zone systems, secondary multiplexes can be connected to a primary multiplex, but must be set up either as separate systems (within a separate system frame) or at very least outside of the system frame for the packaged single-zone system.’