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Mod-Con Boiler Pump Speeds
Greetings. I am the new owner of a Viessmann Vitodens-100 mod-con system for my heat (single zone baseboard) and DHW. The system has a primary-secondary loop configuration, with a low-loss header connecting the loops. Three Grundfos 3-speed pumps: on the primary loop, the radiation loop, and the DHW.
Currently, all three pumps are set to 10 GPM.
I'm wondering how to know if this is optimal. For example, would a slower pump speed to the radiators result in a larger delta-T? If so, should the primary-loop pump be slowed down also? The Vitodens HX has a max flow rate of 6.6 GPM.
I'm afraid I know just enough about these systems to be dangerous, so any advice would be appreciated.