Splitting existing hydronic zone without new lines

[Davidv851]

Hello. I'm planning on some changes to my heating system (hoping to save on heating costs this winter), and I want to see if what I'm planning will work (or, more to the point, what issues there may be in doing things this way). As of now, there are 2 zones on my ~3500 sq foot home, hot water / copper baseboard. During the winter / evenings, we really only need to heat the bedroom. I have a programmable thermostat downstairs to allow that, but there are 2 bedrooms upstairs on the one zone / loop, and a single feed / return feeding them. Would I be able to install zone valves upstairs, keeping the shared feed and return? I realize that reducing the zone size too far can lead to noise / erosion / etc, and that I may need to adjust the thermostat / hydrostat settings to avoid short cycling the boiler and maintain flue temperature, but is there any hard and fast reason not to do things this way? I don't mind work / fine tuning things, but if I can I'd really like to avoid running new lines from the basement to the second floor.

 

[Dana]

Before diving in, first run some of the napkin math analysis:

What boiler (model/make, DOE input/output BTU) is behind all this?

How many feet of baseboard would there be (separately) on each of the newly subdivided zones?

How many feet of baseboard is there on the other zone, that won't be divided?

Run a fuel-use based heat load calculation (wintertime fuel use only) to determine the boiler's oversizing factor for the whole house load, and individual zone loads. For Wayne county locations use 0F as the 99% outside design temperature (yes, I know it gets a lot colder than that sometimes.)