In the process of hooking up my hardy h4 boiler, and the pump is burnt out. It no longer has the taco 009 that came factory. My question is should I use the factory size taco 009 or could I use a 007? I have a loop of 1" pex about 25 feet from the boiler to my furnace heat exchanger, and back to the boiler. The heat exchanger is rated at 120,000 btu.