Hi Gang,

I'm trying to complete some energy calcs to convince myself to go hydronic plus separate AC vs. FHA and AC. But one "deal killer" occured to me.

Assuming an 84% AFUE gas boiler, what will the REAL AFUE be during June-September when I am only needing abuit 2.5M BTU input to make DHW? This is for a 50MBH IBR gas boiler. Any ideas? Seems that the summertime AFUE is going to be kinda low comparted to a chinzy standard tank.