Tankless water heater circuit design...

I'm trying to come up with a design which incorporates a single tankless heater that heats both domestic water and a closed loop radiant heat system. I've seen it done but not the design involved too many componants to make it reliable.
Any ideas greatly appreciated.
Mike
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Perhaps I missunderstand but that sounds like the standard Combination ("Combi") boiler used here in the UK. All done in the boiler itself. has four pipes... Cold in, Domestic Hot water out, Flow and return for the rads.
Not recommended if you need high flow rates on the DHW (eg two showers at once).
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I've seen it done, but the first thing you need to do is figure out what your heat demands are for both systems. Basically if you have a small structure with one or two tenants, you could get away with using a tankless water heater for the radiant floor heat and in the loop you can use a heat exchanger for your domestic hot water. In most cases with larger homes and higher hot water demands, you'll find that you're better off with two separate heaters, unless you use a heater that has two separate in/out.. One important thing to remember is that the piping for each system must remain separate. In other words you can't use the water from the floor heat as domestic hot water.
--
hawgeye



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Not sure where you live but around were we use clycol in our floor heat as if power were to go off you would frezze the syteme also The tankless would run more than reguler tank as it would be doing more than it was designed for so your power savings gone, Also check to see if warranty would cover it
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