+1 on this. You don't want your return coming back below 140° or the condensation will bring an early death to your owb. Just because you are running at hotter temp doesn't mean you'll burn more wood. The fire is only going to burn to bring temp back up to set point, to reheat water the 10-15° between differentials. Myself, I prefer 180° with a 165° low for a little safety net on the bottom in case it gets hit with a load right at the kick on point so the fire can get going in time.
sorry, but i really don't agree with you on this..
my mahoning 400 only burns in the heating season, but, it is set @ 185-190 when temps are/average below 30 F.(now)... it supplies a 125 gal. nurse tank in the basement that is set at 140 this time of year...
so my return temp has NEVER been above 140 deg, i'm heating about a 5600 sq. ft. house, and another 1800 sq. ft. garage (when i turn it on)..
the house was built with radiant heat in mind, so it's all radiant floor heat, including garage slab, and basement slab (basement has'nt been on since i built the house)..
i'm now on my 12th heating season with no major issues........ i figure the owb paid for itself by the second season..
i dunno what your talking about when you say "condensation" will bring an early death to my owb ???
mine is an open system btw..