MNB-Vx actuator block output shows 'NaN' instead of a valid position

[Product_Support]

Issue

The output of the actuator block in a MNB-Vx sometimes shows 'NaN' (Not a Number) instead of a valid position. The only way to clear it is to drive it fully open or fully closed. The issue is intermittent and it is not specific to the same installed controllers. It appears on different controllers at different times.

Product Line

TAC IA Series

Environment

MNB-Vx

Cause

The actuator can be initialized to avoid displaying 'NaN'. The setting in the VAV actuator block is called InitMode. Here's a description of this setting from the WorkPlace Tech Engineering Guide Supplement (F-27356):

Abbreviation	Configuration Property	Description	Range
InitMode	Initialization Mode	Class: Enumeration - The initialization mode configuration property controls synchronization of the VAV object position output after a rest. 0 - No automatic synchronization of the position output. Synchronization occurs when normal control causes the actuator to drive full open or full closed. 1 - Actuator drives full closed after a controller reset to synchronize position output 2 - Actuator drives full open after a controller reset to synchronize position output	0-2

If InitMode = 0, and the actuator doesn't drive full open or full closed for a long period of time, the NaN value will continue to be displayed.

Resolution

Ensure InitMode is set to either 1 or 2 so that it synchronizes after a power cycle or database download.