I have been in contact with the Coal-Trol rep and have gone thru the suggestions. At this point, I have one blower plugged into the controller and one plugged into the wall. With that configuration, I experienced the same blower shut down issue yesterday about an hour after the thermostat called for heat. The blower that was plugged into the controller stopped, the other one continued to run. The difference this time is that it happened in the afternoon (instead of the morning), however STILL about an hour or so after the thermostat called for heat. It's not an overheat issue as both blowers are warm, not hot to the touch.
When the blowers shut down there is ALWAYS a grinding type of noise that is relatively loud and precedes the shutdown. There are no debris in the impellers. I'm wondering if the controller is calling for 100% blower speed and then, for reasons unknown yet, immediately changes that request to 10% as an example. The blowers are spinning 100% and then they are directed to run at 10%, I'm curious to know if that scenario would generate the noise I am hearing.
In any event, the rep suggested I call Neil or Ed. I will do so as soon as my schedule permits.