HO looking to learn....

I'd posted before & learned that the rate at which water moves thru my baseboard affects the BTUs it radiates. --Water moves too slowly, and the BTUs decrease - push it too fast and you get condensation in the boiler. I have question about this condenstation. Plus, isn't there an inefficiency if the water's moving too fast to stay in the exchanger long enough to be heated properly? I guess there's a proper ratio between how big the exchanger is, versus how fast water can move thru it & still be heated properly.

I'm guessing that the condensation will occur if the water in the heat exchanger is cold enough, it will cause water to condense on the inside of the exchanger, causing it to rust in some cases. Morale of the story is that you don't want water to be that cold when it's entering the exchanger(?) However, my furnace doesn't do potable hot water, so if heat's not called for, for a long time, the boiler will go down to room-temp. When the burner fires up, you've got heat in excess of ~800degrees - that 65degree room-temp air is below the dewpoint inside the exchanger at that point, and condensation should immediatly start occuring.

What's the greater evil? Having a contractor install a more powerful circ, to squeeze out more BTUs, or the condensation that occurs when the burner fires up inside a 65-degree heat-exchanger?