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separate boiler/system pump required?
I am designing a new hydronic system to replace steam, using new radiators (runtal) and a knight ModCon boiler, approx 70000BTU. I want to have individual thermostats at the radiators (european style). Massachusetts.
It seems the standard is to have separate boiler and system pumps to not overheat the boiler. I am, however, considering to use a single pressure regulating variable speed pump. It seems to me that should work great to minimize return temp to get boiler to condensing temperatures. I would plan to couple this with a flow switch that only activates the boiler at the allowable minimum flow (no bypass valve since constant pressure).
Any reason not to do this? The only disadvantage that I could see is that if only a single radiator requests water the flow might be too low to start the boiler. I think I could live with that, since in a well balanced system another boiler should request water soon, and with a single radiator the system might short cycle anyways... .