Well I am finally going to attempt to install my system. I am using an OWB and will have two main zones that will run off heat exchangers. The first zone will be for my house and I (unless I am im influenced otherwise) have decided to use the Ultra Fin hanging radiant system which requires no mixing (hopefully) and then for the rest of the house I will be putting in a combination of panel radiators (if my pocket book can afford it). The house system will be a home run distribution system with the Ultra Fin and one zone of the panel radiators (in the upstairs) controlled by thermostats controlling their valves. The next zone will be a couple of panel radiators in series with TRVs on them. The second main zone will be at another building with in-slab radiant heat that will require mixing. With all the great input I have received on this site ...and then with spending a lot of time reading Sieganthaler's book hopefully I am coming at this as somewhat of an educated novice now. What I would like is feedback on my piping scheme which I have attached. I still have to size the pumps, radiators etc. I know what what my heat loss calculations are and will be working on all that next ...but I do not want to make any mistakes here so again any feedback on my layout would be appreciated. If I am way off base I want to know! RH