Heating Help

Plate and frame heat exchangers for Domestic

Does anyone have input into plate and frame heat exchangers for domestinc hot water. Boiler provudes hot water to storage tank, radiant load comes from tank, snow melt comes from tank and a small 5-6 GPM heat exchanger provides domestic hot water. My problem is how to get a recuirc line piped in for domestic hot water, it would need to flow through the heat exchanger on a timer but not sure how.