I agree. The exchangers don't need to be very large.
My parents house uses a hybred, tankless, pulse-fired, natural gas, water circulating, boiler do-hicky for heat and hot water.
It has 3 exchangers in series in a forced air duct. Each exchanger is about 14" x 16-18". Works great. BTUs? No idea, but it doesn't run more per hour than my regular furnace.
Their's is a big house. About 9500 sq ft.
The exchangers look exactly like small car radiators.
Some VW Rabbits had radiators with a seperate fill and cap assembly in the hose, meaning it only had 2 in and out holes. No extra 'holes' to contend with. Would be good for this?
G-
