I think it depends on the details of the install, if you can install it directly in line of the cold line input and the boiler, I think that works fine. But I

I think it depends on the details of the install, if you can install it directly in line of the cold line input and the boiler, I think that works fine. But I think instead often the heat recovery is installed somewhere in-line after the boiler, to make piping easier, but it makes heat management obviously more complicated.