When describing an HVAC system that uses a water heater to provide the hot ware for the space heat (Combined Hydronic), the software will perform calculations for the boiler that account for both the Domestic Hot Water usage as well as space heating usage.
Since the calculations must be done for both the HVAC and DHW usage, you must include BOTH calculations in your scope under the calculation options when modeling this type of system.
One option is to change the system type to a conventional system at the System Level of the Tree, Residential tab.
Your other option is to select the Calculations on the lower left. In the list that appears above, select the specific calculation you are running. On the right, check the options to include both Mechanical and DHW calculations.
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