I have this pump pictured attached to my furnace. I actually have two of them. This one, however, is on a circuit that has been empty for a few years and is now rusted shut and needs replacing. I have a plumber coming to replace it and just took their word at the cost, but then I got to thinking that I should maybe do a quick web search for comparison.
It seems that Grudfos makes a whole lot of these types of pumps. Pexsupply sells quite a few of them:
Alas, I really have no idea how to determine which (if any) is a match to the one I have. Can anyone tell if the pump I have matches any on that site? If not, anyone know if the pump I have is still being manufactured and, if so, what it might cost?