I asked a question a few weeks back about choosing circulators correctly for a radiant heat flooring (thread here
I'm now on to the plumbing design and I have a few more questions
As little background, I settled using radiant floor heating on the first floor, and I'm going to use a heating coil through the Unico high velocity system to heat the second floor. This will also serve as a secondary heat source for the first floor.
My three loads look as follows:
Unico heating coil: 140F water, 10gpm flow, 14.6 ft max head
Floor Zone 1: 120F water, 4.2gpm, 9.6ft
Floor Zone 2: 120F water, 9.2gpm, 14.5ft
In total, I need ~110K BTU/h, ~60K from the two radiant heating zones and ~50K from the heating coil
Currently, I have an old water heater that I would like to use if possible for DHW. At a later date I would like to add an indirect water heater to the system.
Questions I have:
1) Does my design look reasonable? Are there any glaring issues I haven't noticed? Is it advisable to run the heating coil, which requires a higher temp, in series with the two radiant floor circuits as drawn? the floor circuits are in parallel to each other.
2) I'm in Illinois, where we have wide temperature swings. In the spring and fall it can oscillate between 40 and 60 over a day, which doesn't always work well with radiant heat. How can I best setup the heating coil and the floors to run together? The heating coil is the ONLY heat upstairs, but on the first floor I have both radiant and vents. Is there a good way to be able to switch which is the primary heat source? In the deep winter the floor should be primary, but in spring/fall it should probably be
3) Would it be a better design to combine the two pumps that go to the radiant floor zones into one, and do zone controlling with actuators? I can't imagine a scenario where I would have the heat totally off in one zone and not the other, only reason to have two different pumps is manifold placement/temp control for bedrooms vs common areas.
4) Does anyone have a good recommendation for a boiler to use? I've oscillated between tankless, Polaris water heater, combi boiler. I want to make sure I'll be able to expand later with a tanked unit, but also so that with just the three heating zones I won't be short cycling.
Plumbing layout attached.