My pump was making noises, so I replaced the cartridge a few months ago. The pipes are now ringing, especially on the return side of the boiler (this is NOT gurgling noise, pipe banging, etc...). Using a screw driver for sound pickup, the circulation noise is much less on the exit side of the boiler.

The pump was the older 0010-F1. I ordered the "correct" replacement cartridge. Prior to installation, I noted that the impellers were quite different. The old impeller was closed (similar to a higher head model- looks similar to the impeller of Tac0012-011RP ) and the new one was relatively flat and open. I called Taco, and they assured me it was the correct one. I'm now thinking that sometime in the past, and possibly at the original install, a different cartridge was plugged in from one of the higher series pumps.

Here's what I have:
112,500 BTU McNeil
2 story home ~1350 SF per floor
2 loops, one 1st floor, one 2nd floor with auto valves
220 equivalent feet of piping in the highest head loop
3/4" piping system
Burner in the basement
0010-F1 pump, 1/15 hp, 3250 RPM

Questions:
Does anyone have any direct experience with the interchangeability?
What size replacement pump would be appropriate? I did some calculations based on this link, http://www.taco-hvac.com/uploads/Fil...irculators.pdf and it looks like I need a Model 0012 which would give me a head versus flow crossing point of ~6 to 7 gpm (or am I totally wrong?). This would tend to support the cartridge swap theory.
Or would the Grundfos UPS15-58FC be a good choice?