I have a flat plate heat exchanger that exchanges the boiler hot water to heating and domestic hot water. The water leaving the heat exchanger is 150 degrees F. The return water is around 80 degrees F. Would I gain anything by using a mixing valve to mix the 150 degree F water with the return 80 degree F water. The 150 degree water has heated the house and two out buildings and supplied domestic hot water even at below zero temperatures with no problems. If I put a mixing valve after the heat exchanger and mixed it with the return 80 degree F water, would I gain anything by lowering the heating and domestic hot water to 120 degrees F. I know 150 degree F domestic hot water is dangerous, but I live alone and have adjusted knowing not to turn the hot water on without the cold.