Indirect Storage tank inputs and outputs used with Tankless FlowMax90 boiler issue / question

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New Member
Jan 25, 2023
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Georgetown, Ontario
I have an indirect storage tank being used in my home heating system (hot water is generated from a tankless unit and stored in this tank to be used by domestic water).
The tank is a GIANT 142ETE-9G7M.
It has two inlets on top. One inlet is connected to my furnace (hydronic air handler) that uses hot water coils (always hot) and the 2nd inlet has my House COLD water coming into a thermostatic mixing valve (COLD SIDE), and the HOT side of this valve comes from the Storage tank (2nd inlet), the MIX outlet of the mixing valve goes to my domestic hot water needs (faucets etc) I've attached some crude pictures (sorry) for reference.
This 2nd inlet is sometimes HOT (when my faucet is on I'm assuming hot water is coming out from here???) and then freezing cold (when no faucets are in use and cold water coming in from source??)
Can this mixing valve let water pass through from the COLD side to the HOT side (this is the only way I see water coming into the tank)??

My end game is to completely REMOVE this mixing valve as it's hit and miss with the water temp and simply get cold water into the tank from that inlet but that means I would have to use the 2nd inlet as HOT both incoming and outgoing - is this possible with a storage tank (one inlet with water going both ways ??)

I am not a plumber by any means and ANY help would be greatly appreciated.
My local plumbers (two that I've called so far) have no idea ?? which baffles here I am asking on a forum hoping for some clarification.


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