Combination water heater/space heater

Hi all. I inspected a home that had hydronic baseboard heaters, heated by the water heater that also supplied the potable water. There were cold in/ hot out lines for the potable water and cold in/hot out lines for the space heat.
The seller made a disclosure that the potable water is used for the space heater as well. I think he is incorrect but I wouldn’t mind having some expert opinion on this as well. (Tomorrow I am planning to call the manufacturer, GSW.)
I am aware of systems that have no separation between the two but they have to have a provision that allows the water in the space heater to recirculate to prevent stagnation. That works fine if the lines go to an air handler but if the water has to circulate periodically through baseboard heaters, it would automatically heat the home some, even in the summer.
Aside from that, systems that do not have a separation between potable water and space heat water would not have two sets of lines going into and out of the heater would they?

Eagerly looking forward to an answer.

Research and changes going on last 10+ years with trying to combine water/space heating into one compact unit.

Bradford White makes a combo unit.

have seen a similar configuation within Condos we are currently working within.
Water Heater supplies domestic water as well as the water supply for the Hydronic Heat of the HVAC

Other manufactures have come up a similar design. It should say on the unit that it is acceptable for potable water and hydronic or be a combo system as was pointed out.:smiley:

Thanks guys. The Bradford White diagram clearly shows that the potable water is separated from the heating loop by a heat exchanger. I haven’t been able to find if the GSW system does that as well. I kind of doubt it because the installation instructions say that an expansion tank is only needed if a backflow preventer is installed. With a closed loop, an expansion tank would be needed regardless.

Please allow me to be a bit offtopic, would just like to say thanks for this thread, gave me a great idea to include such heaters on my site about space and water heater reviews and info guide. It fits into the topic greatly. Thanks again.