

Just chiming in to say I think this guy’s got the right idea. I realize what community this is posted in, but sometimes when you’re really into your hammer everything starts to look a little too much like a nail. If you have room for it (sounds like a pretty big house) a buffer tank would make a huge difference




In most hydronic heating systems I’ve worked on, there’s an insulated tank of hot water either somewhere in between the boiler and radiators or built into the boiler directly. The thermostats talk to valves that send the water to radiators in the rooms that need it. The boiler just keeps that water at a set temperature.
In larger buildings with really long runs, sometimes there are valves to bypass certain radiators and/or multiple tanks located around the building. I can’t say without more information about your home, but it might make sense to have one near the area you’re trying to heat most.
No storage tank at all and thermostats that fire up your boiler directly sounds very unusual and inefficient. The expansion tank you have is just meant to stabilize pressure, it doesn’t have enough volume to do much for temperature