Joel, one last thought occurred to be last night. I realized that the air handlers run independently of the furnace. In other words, if the thermostats are calling for heat, the fans will run even if the remote switch in the coach is turned off. The remote switch connects to the brain with (according to this version of the manual) a telephone type connector and if this circuit is interrupted the systems would be exactly what your are experiencing. It might be worthwhile to check this connection. There isn't any good circuit diagrams of the remote switch but I suspect that the indicator light on the switch panel would be out during the occurrence of a problem. Also, the switch panel does have an alarm that sounds if any internal problems occur. The fact that you system did not enter an alarm condition really suggests something simple.
If you look at the brain box, there is an indicator light that shows if the remote switch is on and (I believe) a light that says remote is off.
In keeping with the KISS principle, this would replicate your symptoms perfectly.
Dick--
Thanks for continuing to think about the problem. I think the fact that mitigates against this being the case is that the circulating pump is running when the thermostats are calling for heat. I think that means a signal is getting to the board indicating that heat is needed. (Also, the remote OFF diode is not illuminated when this happens--there is no remote ON, only off).
I spoke with Kevin Lambert at ITR earlier today and I'm waiting for him to call me back again so we can run through some quick diagnostic tests. He agreed that the problem was consistent with what would occur if the operating aquastat was sticking.
Joel
