Hello been looking for awhile and had a question I’m getting ready to plumb for a owb and need some help or opinion. I like to go from boiler to heat hot water and my house has two heat exchanger s should I plum every thing in series or separate runs also have a heat exchanger in a attached garage
I have almost the same setup you do. I have an upstairs water to air and a downstairs water to air. Flat plate downstairs and a garage water to air. I put the downstairs plate and water to air on 1 series circuit and my upstairs water to air and garage on 1 series circuit. 2 pumps, 2 supplies, 2 returns. But, my water to airs are much larger and both heat larger spaces than yours. Like Yoder said, I do plate first then water to air with a bypass for summer burning. Could it be done differently? Yes. Is this simple? Yes. With this design I have ZERO concerns about my return temps being too low. Both pump circuits have about 20' of head and I get plenty of flow.
If I had my flat plate, downstairs water to air, upstairs water to air, all in series, I would def put in a mixing valve before it gets back to the stove. Having the 3rd water to air in the garage would be even more justification. I think that would be too much for 1 series circuit.