I'm blaming the product because I think the system is unreasonably fickle. It works as long as I'm babysitting it and spending hours and hours learning how to be an HVAC contractor. Again, how do I sell this house? Do I give the new owner 2 weeks of hvac training? Do I tell them welcome to the house. If you don't handle the hvac yourself, expect to have 20 calls/year to the hvac guys? In this last case the incoming water was 52/53 and never went below that. The valve apparently doesn't adjust quickly enough or properly enough and as a result it sucks too much heat out. Or maybe the Lt2 thermister is whacky. I'd still say that proves my point that the systems is too fickle to be practical. Maybe I'll have much better luck now that I'm not using the modulating valve configuration.