Why don't my inline booster fans operate as expected?
Has your furnace/AC unit been sized for the addition?
Try unplugging the fans from the ducstat and plug them into a regular outlet and see if they continue to cut out.
Keep in mind that these fans will only help move the air that's available from the main blower, they won't increase the air available. Your run of 8&quot; duct and then split into 2-6&quot;ducts is going to have a lot of resistance to air flow. Those two fans will help accelerate the existing air to it's destination. The plenum and main blower will supply a certain amount of air for the entire house, the fans won't increase that amount.
The strain on the fans due to the lack of air could be overloading them and causing them to kick out.
I've seen this a lot on this site and one of the good solutions is to add a mini split system for the addition because you're probably taxing your existing system.