You'll notice in the drawing that I linked to above that the return line goes to both the cold water inlet of the mix valve and to the tank but they are separated by a check valve in the cold line. Also notice that each of these lines has a valve to regulate flow (preferably globe valves). With the system piped and operating per our drawing and there is no draw from the system you're correct that the cold inlet will be too warm. This is the reason for the globe valves to regulate flow to the cold water inlet and through the tank. During this time, the mixing valve is not a big part of the equation.
I hope that this helps. If you have any further questions, please call our office and we'll be happy to help
Cody Mack
Applications Engineer
Caleffi NA
414-335-6217
Sorry for the late reply!
We do have a diagram for that exact scenario. Please see page 6 of the linked document below.
https://www.caleffi.com/sites/default/files/file/01050_17_na.pdf
You'll notice in the drawing that I linked to above that the return line goes to both the cold water inlet of the mix valve and to the tank but they are separated by a check valve in the cold line. Also notice that each of these lines has a valve to regulate flow (preferably globe valves). With the system piped and operating per our drawing and there is no draw from the system you're correct that the cold inlet will be too warm. This is the reason for the globe valves to regulate flow to the cold water inlet and through the tank. During this time, the mixing valve is not a big part of the equation.
I hope that this helps. If you have any further questions, please call our office and we'll be happy to help
Cody Mack
Applications Engineer
Caleffi NA
414-335-6217