I'm remodeling my basement and want to zone it. The existing heating system uses continuous 1 1/2 inch piping running around the perimeter of the house with venturis at each radiator. In the remodeled basement I'm using baseboard radiators with 3/4 inch plumbing.
At first I was just going to get a 1 1/2 inch zone valve for the upstairs heating and the run of the mill 3/4 inch for the basement, but the largest zone valve I can find is 1 1/4 and they are expensive. While I could use this with reducers, I didn't know if this would restrict the flow too much to the upstairs heating.
So, I got this bright idea that I would split the 1 1/2 supply line out of the boiler and use two 3/4" or 1 inch zone valves in parallel and combine back to 1 1/2 inch on the other side.