[EnergyPlus_Support] Sever in Sizing:Plant object with WaterHeater:Mixed [3 Attachments]

["m.aldegheri@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>]

Dear all,
I have a problem in this .idf I modeled the HVAC shown in the picture.

It is a HW heating system fr a building in which each thermal zone is heated by radiant panels. In the .idf there is only the supply side of the HW loop and a schedule was used to simulate the heating demand to to loop.
A double tank system for the DWH production and storage is modeled. The DHW system is assisted by a solar loop. The main idea is that the DHW is firstly produced using the solar loop heating contribute and than, only when it need, the HW loop integrates the production of water.
The HW loop should be sized using a boiler exit temperature of 50°C with a temperature difference of 10°C.
The DWH should sent to the users with a maximum temperature of 45°C.
My problem is that the sizing:plant object for the HW loop requires an exit temperature >=58°C because of the sizing requirements of one of the DHW tanks, but I can't understand why.
E+ gives return me this error:

   ** Severe  ** Autosizing of Source side water heater design flow rate requires Sizing:Plant object to have an exit temperature >= 58C
   **   ~~~   ** Occurs for WaterHeater:Mixed object=TANK ACS
   **  Fatal  ** Preceding sizing errors cause program termination

How can I solve this problem, considering that the sizing temperature for the HW loop should be 50°C and not 58° or more?

I'm uploading the idf, the scheme and the heating load profile for the execution.
Thanks a lot.

Marco

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Posted by: m.aldegheri@xxxxxxxxx

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Attachment Converted: "D:\Eudora\Attach\HVAC SCHEME.png"

Attachment Converted: "D:\Eudora\Attach\CARICO TERMICO HVAC.txt"

Attachment Converted: "D:\Eudora\Attach\HVAC example.idf"