Well, I've read enough on this site to convince myself that my NRF-25 isn't moving the water fast enough. I just ordered an NRF-36. My OWB is 180' from the house, pump in the basement, but my entire system in the house is 1" copper, no pex at all, which means lots of 90's and 45's. It cost a little more but boy does it look sweet!!! I was losing 30 degrees across my 20"x 20" HX and from what I'm reading, that's too much. As Scott7m stated earlier, "another common case of, well my home is warm so I know my pump is big enough". Guilty as charged Scott.