Zone Setpoint with Demand and Learning Adaptive Optimal Start
Learning Adaptive Optimal Start is a routine used by certain Zone Setpoint microblocks to regulate setpoints so that the ideal temperature range can be achieved when building occupancy begins. This routine adjusts setpoints based on the heating or cooling capacity of the equipment, which is adjusted (or learned) over time as the equipment meets or fails to meet the ideal temperature range. If the zone's ideal temperature range is not reached by the time occupancy begins or if it is reached too soon, the Learning Adaptive Optimal Start routine adjusts the heating or cooling capacities of the equipment up or down for the next unoccupied period. You determine the amount of the adjustment, depending on the color actually achieved at the beginning of occupancy, on the microblock's dialog or on the Properties page. The following formulas use the adjusted heating and cooling capacities to calculate the current setpoints: NOTE The following formulas are used for ExecB control programs. Heating setpoint during optimal start period t = time remaining until the transition to the occupied state (hours) OAT = outside air temperature (°F) HDESIGN = heating design temp Learned HCAP = learned heating capacity HUNOCC = heating setpoint when unoccupied HOCC = heating setpoint when occupied H1 = (HDESIGN - OAT) / (HDESIGN - 65F) * Learned HCAP H2 = HUNOCC + ((12 - MIN(t,12)) / 12) * (HOCC - HUNOCC) H3 = MAX(MIN (H2, HOCC - (t * H1)), HUNOCC) HSP = H3 + (H3 - HUNOCC) * (1 - (H3 - HUNOCC) / (HOCC - HUNOCC)) Cooling setpoint during optimal start period t = time remaining until the transition to the occupied state (hours) OAT = outside air temperature (°F) CDESIGN = cooling design temp Learned CCAP = learned cooling capacity CUNOCC = cooling setpoint when unoccupied COCC = cooling setpoint when occupied C1 = (CDESIGN - OAT) / (CDESIGN - 65F) * Learned CCAP C2 = CUNOCC + ((12 - MIN(t,12)) / 12) * (COCC - CUNOCC) C3 = MIN(MAX (C2, COCC + (t * C1)), CUNOCC) CSP = C3 + (C3 - CUNOCC) * (1 - (C3 - CUNOCC) / (COCC - CUNOCC)) NOTE The following formula is used for older control programs:
Because learning adaptive optimal start uses learned capacities, the optimal start calculations are more accurate and equipment is controlled more efficiently. The current learned capacities are displayed on the Properties page and are available to other parts of the control program from the microblock's HCAP and CCAP outputs. In both Cooling and Heating modes, if the zone temp has undershot (not reached) the setpoint when the zone transitions into Occupied, the capacity is reduced by the adjustment value. The next time optimal start is in effect, the ramp to the occupied setpoint will begin sooner because the capacity figure has been decreased. Likewise, if the zone temp has overshot (exceeded) the setpoint when the zone goes occupied, the capacity will be increased by the adjustment value. The next time optimal start is in effect, the ramp to the occupied setpoint will begin later because the capacity figure has been increased. Example The heating capacity for the zone is 5 degrees per hour. When the zone becomes occupied, the zone temperature is 1 degree below the occupied setpoint, indicating a need for additional heat. Since the zone temperature was low by 1 degree, the heating capacity will be decreased by the light blue Learning Adaptive Optimal Start value (1 degree below setpoint is in the light blue region). If the light blue Learning Adaptive Optimal Start value is 0.06, the heating capacity will be adjusted to 4.94 for the next optimal start period. This causes the setpoint adjustment to begin sooner in the next unoccupied period. Enter the Learning Adaptive Optimal Start values on the microblock's dialog or on the Properties page. The learning adaptive optimal start routine will not adjust the learned heating or cooling capacities to lower than .0625 or higher than 15.938 degrees per hour. The adjustment value is either added or subtracted to the capacity, depending on whether the zone temp is on the "comfortable" side of the setpoint or the "uncomfortable" side of the setpoint when the zone transitions to the occupied state. If you are using learning adaptive optimal start, be aware that learned capacities can be distorted during override periods. For this reason, you should prevent learned capacities from being adjusted during override periods by using the microblock's LRNI input. When this input is turned on, learning adaptive optimal start will still occur, but the learned heating and cooling capacities will not be changed from the previous unoccupied period's values. Also, make sure that all other control sequences in the control program, including PID loops, are tuned and functioning properly before using the learning adaptive optimal start microblocks. Otherwise, setpoints could be improperly adjusted. NOTE Alt+click any value in WebCTRL to view property details, including its expression and editing privilege. | |||||||||||||||||||||||||||||||||
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