Hydro Air, zones and tankless sizing...

[Roland]

Hello..

I'm considering replacing multiple gas furnaces, which provide zoned heat, with a hydro-air system. My question is: If I have multiple air handlers (one handler per zone), can I use a single tankless "boiler" to feed all the air handlers? The concern is that all the zones will not be calling for heat at once, so is there a tankless boiler size that will work?

For an approximate/theoretical example, if I have four 100K BTU air handlers, can I spec a 400K BTU tankless even though much of the time possibly only one zone (100K BTU) would be calling for heat?

I assume for a traditional tank boiler, this would be a bad setup because it would short-cycle or have significant unused hot-water/capacity that would be wasted. But, with a tankless, possibly this zoned sizing isn't an issue since the boiler would be heating the water on demand. Any thoughts or experience with this?

Thanks!

 

[Fitter30]

Boiler that has a high turn down would be my pic. 400k would be the worst case. Condensing boilers/ combi are most efficient with return water temp 130*f or cooler 95%+ above 130* 86%, the longer the run time is better for the boiler. Even at night living areas and bedrooms usually get turn down, day time bedrooms might be turned down. Pumps look at e series taco pumps.