Bill,
Still curious about one thing, if you daisy chain the two demand heaters how do you regulate the heat. I want to use two 199,000 BTU Takagi's. The heated anti-freeze could be very hot while entering the second unit. I realize this is a way for the heaters to keep up but not sure how I would regulate each units output.
Thanks,
Buzzie
I was reading through this website today and I thought that I read they were running glycol through their Takagi units:
http://www.radiantcompany.com/heatsources/Takagischematics.shtml
Your suggestion on running two feeds to the manifold from each unit independently makes sense.