Unknown Shutdown
Why is this happening?
Airflow Limit or Blower Cutback
We occasionally get calls where someone has a zone system that just shuts down the system. Before doing anything, its best to go into the fault history by going to the master thermostat and clicking on the menu icon, service and history. Its likely that the unit is shutting down either as a result of an airflow limit or on blower cutback.
Each zone should have it's maximum airflow limit set. This for all intents and purposes is a noise or sound limit for the air coming out of the registers. If the limit is set too low for any zones, it can take the system below the lowest capacity if just that zone is calling. Go to settings, and zoning and see what each zone's airflow limit is set for. If there is an asterisk flashing, it means that zone cannot provide enough air for the system to run if only that zone is calling. You can adjust the airflow limit up until there is no asterisk.
If the limit is set too high, or to unlimited, you could potentially have too much noise in the zone or if the zones are restrictive, the blower motor may hit maximum RPM and be unable to provide the umpph needed before providing enough airflow. This would result in a blower cutback. For two stage equipment, remember the lowest capacity of the equipment is about 70% of full capacity. If you have two zones or more there may not be enough or available air on one zone to keep the system online. It may mean a bypass is required or you need to set overconditioning for the other zones so it can allow dumping of excess air into another zone or two.
