well, at least to me. i am getting warm water out of the tap instead of hot. it makes no sense to me. heres the setup - wood boiler in parrallel with the oil boiler, hot water coil in the oil boiler. when i was playing around with this the wood boiler was circulating water at about 170 degrees. i shut the valve for the cold water right before the mixing valve. no effect on temp or pressure at the tap. the plate that the coil is attached to is very hot. the pipe for hot water out is warm. the cold water in is cold. the well for the aquastat is very hot. so, this has me baffled. why am i not getting hot water? the pipe on either side of the mixing valve is the same temp. been down the broken mixing valve road before. could the hot water coil have built up some type of scale on the outside that basically insulates it? i'm stumped, and taking warm showers.