Definitions of terms used in the Unmet Load Hours range test
The terminology used in the range test tools for unmet load hours is somewhat specialized. The following definitions may therefore be helpful in using the Range Test dialog for unmet load hour tests:
- When Occupied: All times for any particular room when occupancy is greater than zero.
- When room heated or cooled: Tests for hours out of range relative to the setpoint profiles at all times for each particular room, so long as the value for the on/off profile for either heating or cooling = on. If there are warm-up and after-hours operating periods over which the daytime setpoints are extended, this test will use daytime setpoints during these time periods. This test does not allow for room temperature transition from setback to setpoint.
- When plant profile on full: All times for a particular room during which the normal daytime setpoint should be fully met—i.e., fully excluding unoccupied/nighttime operation (outside of “opening hours”) and both morning start-up and after-hours operation.
- When conditioned (incl. setback): Tests for hours out of range relative to setpoints, applying the unoccupied/nighttime setback values to any morning start-up and after-hours operating periods during all times for a particular room when the on/off heating or cooling profile = ON. This test assumes, for example, that the full morning warm-up period will be needed to raise a particular zone from the setback temperature to the daytime setpoint, and therefore does allow for room temperature transition from setback to setpoint.
- Between room setpoints (+/- differential tolerances): Test to count hours in three categories:
- Below the heating setpoint minus the heating control band tolerances
- Between room setpoints, +/- the set control band tolerances
- Above the cooling setpoint plus the heating control band tolerances
- Test temperatures in controlled band, tolerances in °F: These values set the added tolerance above and below the setpoints that should be applied to determine when a temperature is “out of range.” The tolerances allow for the throttling or control of HVAC parameters such as variable water and air flow rates in coils and ducts to address loads. The pre-defined systems all reference profiles that have names beginning with “HVAC,” and so long as they are changed only via the System Schedules dialog, these profiles are maintained with standard throttling ranges relative to the heating and cooling setpoints. Unless you’ve set up your own HVAC controller profiles or have revised values in the pre-defined “HVAC” profiles within ApPro, the standard 2 ° F for both heating and cooling when working in IP units (1.11 ° C when in metric) should be used here. If you have set up custom control profiles, you will need to set these tolerance values to allow for the throttling range in the custom profiles.
- Averaged, shared hours (for ‘unmet hours’ test): This looks at average temperature over the full one-hour period in each room for each hour and then adds any particular out-of-range hour to the total “shared hours” tally only once, regardless of how many rooms or zones were out of range during that hour. The “shared hours” total of each column is displayed in the bottom row of the table.
With all conditioned spaces selected, the total of shared hours reported in the bottom row as outside the control ranges for both heating and cooling are collectively the Unmet Load Hours.
A space temperature is considered out of range (under-heated or under-cooled) for any hour when the average temperature for that hour is below the heating setpoint less the control band tolerance or above the cooling setpoint plus the control band tolerance. The “shared hours” might be thought of as a logical ‘OR’ test, with each hour counted only once when any one or more rooms in the currently selected set of rooms is/are out of range.