Ron, I was hoping to get down into the basement to read the name on the system but we gutted the dining room and I can't get to the door. I have my building inspector's report, though. It's a forced hot water system - the boiler's an excellent one you'd probably know but it is old. He wrote, "the leaking pump flanges and tankless heater fitting have corroded due to chronic leaks. Repair is needed before more serious damage takes place." He have the tank an F (I replaced that), the main unit a B-, the burner B+, venting A ('cause it's hogging the central chimney), and efficiency unknown.
Do you know if this kind of system can be power vented? Does the chronic leaking problem sound serious enough to justify replacing it with a new power-vented furnace? I'm looking for a good reason to open up that chimney - I can't bring myself to do it just for aesthetics.