Wait a minute that dosent work your trying to save as much energy as possible you will have hot water at all three areas and you only want it at one place at a time. I thought you wanted hot water but you want it to be cold and then throw a switch which will heat three sections at once instead of just the desired one location getting hot ?
If we decided to plumb it the right way you would be disappointed that the entire hot water system was hot and theoreticaly wasting energy . I cant figure out the energy savings or begin to I was concidering comfort a bucnh of water savings and what I belive to be some heating costs
Heating all 3 outlets at once I see as an advantage as most likely all 3:get used in same small window of time. Morning and evening.
The total amount of water getting heated in the parallel drawing would be 65' of 3/4". -50' WH to manifold plus 15' to outlet.
A complete loop for me would be over 110' to last outlet if temp sensor located there, or 180' if temp sensor back at pump.
So I am not seeing your heating concerns as existing. A complete loop also heats every outlet does it not? Isn't that the whole idea of the recirc pump?
I never had to really think about one before, I am no plumber! They always sounded great and made sense until now that I go to put one in and I see many issues with energy waste. Like I said it seems like a balancing act between wasting water or wasting energy.
Because I live in a town prone to drought I guess waste the energy not the water.