Phoenix Water Heater for Radiant Floor Heating and Domestic Water Supply?

[cloves]

Hi everyone, just to preface I had my radiant heating system designed my the Radiant Design Institute (Fred Seton).

Fred told me that the Phoenix PH100-55 would be able to supply both the radiant and domestic. From what I have been reading I want this system to run in closed system. Which I believe means that the domestic hot water supply is separate from the radiant. What I can't figure out is how it possible for that function correctly? I look at the water heater and it has a inlet and outlet. Best guess is the water stays separate because of the heat exchanger?

Could someone explain the concept to me?

[Dana]

For Phoenix water heaters to run "closed system", the heating loop has to be isolated with an exterior heat exchanger and circulation pumps on each side of the isolating heat exchanger. See the "brazed plate" indicated in figure 7, page 21 (pdf. pagination) in the manual, which is the isolating heat exchanger in the diagram.

Open systems may or may not meet code in NJ, but they're a bad idea in general.