tankless water heater with tank supplement

[camner]

One of the issues with a tankless system is the so called "cold water sandwich." One site has an idea for how to reduce this issue (see http://www.taunton.com/finehomebuild.../021192082.pdf).

I'm intrigued by the idea at the end, which is to install a pump between the tankless and the tank so that the tank is filled by the tankless heater when the thermostat on the tank indicates that it needs to have hotter water. See "The Fix: problem #2" in the PDF)

I don't understand the plumbing diagram for this, though. It appears to use 3 inlets into the tank, when I think there are typically only two.

Has anyone tried anything like this out? Or even if not, to explain how the pipe diagram would work?

[nhmaster]

Oh boy, a chance to spend even more money.

[99k]

It appears they removed the TNP valve and relocated elsewhere. This looks like a tremendous investment ... I can't imagine the payback time for this set-up.

[chris8796]

I would agree with 99k, they removed the TNP valve. They also disconnect the heating element from the tank, so its a storage tank w/o a heater. All of the heating is done by the tankless.