T007_Z: Blower Cutback Caused Shutdown
Status
This is a non-critical fault and only appears in history.
Description
This alert is set when the system static is too high likely as a result of allowing system demand to exceed the airflow capabilities of the duct system or open zones. This is similar to the previous faults of T001_Z through T006_Z with some exception.
Generally in a zoning application this will appear if no zone airflow limits are set in the zoning settings pages.
Cause
An example of why this alert may be set may be that a zone, or zones airflow limit(s) are set to unlimited. When a zone's airflow limits are set to unlimited it does not control the staging of the equipment and can call for far more capacity and airflow than the open zone or zones can handle, which in turn runs the system static beyond the blower curves.
It could also be because the duct work is otherwise simply inadequate or possibly obstructed internally or too many supply registers have been closed. A system that lacks return could also be the cause.
Solution
For the most part, resolving this issue will be done by putting airflow limits on zones or resolving the cause for blockage of airflow in the supply or returns.
Be sure to manage expectations as well. A zoning system is a substitute for multiple systems and there are limitations. As variable speed motors have become more commonplace in the industry, most technicians realize that these motors will overcome more static than a PSC or Constant Torque motor, but they are not an answer to resolving air distribution system issues. ECM motors still have a maximum RPM and can only do so much. Remember, the higher the static, the higher the operating cost of these motors.
