All depends on pump size and delta T when talking temp. Depending on HX size and piping layout, DHW call may be a huge load. Condensation doesn't start occurring until ~132 degree return temps, so if there is good mixing in the stove and a proper piping system, you should be able to run down to 165 with a 10 degree diff or 160 with a 5 degree diff- possibly even lower if creosote doesn't become a problem. Even in the -40F dead of winter I still run a 165 supply with 10 degree diff, and a full load of heating and DHW hangs about a 17 degree delta T. Personally I don't understand the idea of burning year round and needing to have a heat dump when the wear and tear on my shoes walking to the stove twice a day costs more than heating DHW with LP, but that's just me and my small DHW load. Last time I filled my 500 gallon LP tank was in April 2015 and it's down to about 15% right now- a 3 person household has cost me ~$10/mo to heat water as well as the house during shoulder seasons, I can't afford to light a fire for that