The BPRM report for my project shows a lot of Unmet Load Hours?
It is possible to review the simulation results in Vista to locate the source of the unmet load hours.
If you go into Vista, then select one of the results files, select all the rooms then click range test and the following, it should match the numbers that were shown in the output report.
If you look at the range test for the rooms that fail, you can then look at a particular room to see when it’s not meeting the setpoint by mapping the air temperature vs the heating/cooling setpoint in a graph. This should give you some indication as to whether or not the space needs more cooling/heating or there is a discrepancy in the profiles. A common cause can be when you use custom templates and temperature profiles for the spaces instead of the predefined ASHRAE templates. Or, you may have created a new subset of profiles within the system schedules step in the navigator but forgotten to also assign the associated HVAC profiles to the controllers on that system in ApacheHVAC. There is also a slight improvement with V6.4.0.8 with applying the Unoccupied setpoint, rather than Occupied, during the Start-up and After-hours operational periods for the Unmet Load Hours test, as the spaces should not be expected to achieve the Occupied setpoint during these warm-up/cool-down periods.
There will always be limitations with respect to sizing to meet the peak load when zones go from night setback to the occupied setpoint, as ASHRAE requires us to use a steady-state design day condition for the sizing of heating loads, and this doesn’t represent the transient demand. Thus the number of hours set for morning warm-up and the setting for OA off vs. on when the fan runs for heating or cooling in the unoccupied hours are both essential considerations.
The only thing that would disqualify a room from the unmet loads test would be if the heating/cooling profile is set to “OFF CONTINOUSLY” in the room data or thermal template.
Note the range test screenshot is in IP units. Just match it to whatever you have in the navigator for the tolerances if using Metric.
