This is a simple method to install diesel radiant floor heat plus taking heat from the engine while in transit.
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This is actually simpler than it looks and can be done very neatly without taking up a lot of space.

THIS FLAT PLATE HEAT EXCHANGER CAN BE USED TO HEAT THE RV WHILE IN TRANSIT PLUS CAN BE USED TO PREHEAT THE ENGINE WITH ANOTHER CIRC PUMP.
( VERY GOOD FOR DIESEL ENGINES)

The flat plate can be made to heat water without heating the RV but requires another pump and controls, probably not worth the effort.

You can do your own with proper instructions.
    I do offer a design service, cost generally runs $400.00. I furnish an equipment list with assembly instructions, complete instruction book, furnish a tubing layout (I need drawings) with complete tubing installation instructions, and locate the best source of equipment at the best cost to you. I can normally save people thousands of dollars on the cost of their installed system but more important is the fact you will have a radiant system with the highest quality equipment and one that is simple, efficient, easy to install and trouble free.