Hello All! I am currently replacing my heating system. I plan to install a 4 zone radiant heat and domestic hot water off of an unpurchsed tankless water heater. basically i plan to run 2 zones of pex radiant floor heat on the first floor (1300sf) and then baseboard in the master bedroom (entire 2nd floor 600 sf) and also baseboard in the soon to be half finished basement; 2 rooms, laundry (150sf) and office (250sf) As far as installing the PEX tubing, baseboard, and water heater, I think i'm pretty good. I am getting a little over my head when it comes to the different pumps/controllers used for the different zones. I am told that all loops in each zone need to be almost the same size. I don't really see why there are so many different sized pumps. So....first round of questions: What water heater should I get? I am looking at Takagi T-D2-IN but fear it may be an overkill What pumps should I get? I have been looking at the Taco pumps, but don't know what size to get. Different for each zone size? i would assume What controls the pumps. I know obviously a thermostat, but saw something about a zone relay controller or something. And last for now; I have been doing a lot of research, and i have seen a few different set ups. most are similar, but some call for an expansion tank. I don't see the need in an open system. Either way i have a fairly new one from my previous, closed, oil fueled, radiator system. It is starting to get cold, and my pregnant wife is being very patient. I am starting to pipe the gas in tomorrow and want to get everything i need. I would appreciate any help, even if just links to better guides.