5.As actual SAT approaches CCSR value, stages are re- leased. The minimum time delay between stages on de- creasing demand is 90 seconds.
NOTE: Demand for heating has priority and Master Loop will either terminate existing or prevent initiation of Cooling Cycle by issuing a CCSR at the maximum limit. This will cause the CSL to select zero stages of cooling capacity, initiating a stoppage of an existing cooling cycle.
CV Units Ð Supply fan must be ON for cooling control to operate. Sequence is as follows:
1.Master Loop will survey space temperature and space tem- perature offset inputs, then calculate CCSR value.
2.The CSL surveys actual SAT, then calculates number of capacity stages required to satisfy space load.
3.Stages of cooling capacity are initiated. (From zero stages, there will be a 1.5 to 3 minute delay before ®rst stage is initiated.)
UNOCCUPIED COOLING Ð The unoccupied cooling sequence of operation is similar to Occupied Cooling (see above) except for the following:
1.Supply Fan will be OFF as demand is initiated.
2.The Master Loop will start Supply Fan and cooling cycle. Fan status must be proved as ON within 2 minutes to con- tinue with cooling operation.
3.Control set point will be Unoccupied Cooling Set Point (UCSP).
4.At end of cooling cycle, Supply Fan will be turned OFF.
OVERRIDES
First Stage and Slow Change Override Ð The ®rst stage over- ride reduces cycling on the ®rst stage of capacity, and the slow change override prevents the addition or subtraction of another stage of capacity if the SAT is close to the set point and gradually moving towards the set point.
Low Temperature Override ÐThis override function pro- tects against rapid load decreases by removing a stage every 30 seconds when required based on temperature and the tem- perature rate of change.
High Temperature Override Ð This override function pro- tects against rapid load increases by adding a stage once every 60 seconds as required, based on temperature and tem- perature rate of change.
ADAPTIVE OPTIMAL START Ð Optimal start is used to heat up or cool down the space prior to occupancy. The purpose is to have the space temperature approach and then achieve the occupied set point by the time of occupancy. The control utilizes outdoor-air temperature, space temperature, occupied set point, and a ``K'' factor. The ``K'' factor is ex- pressed in minutes per degree, and calculates a start time offset, which is the time in minutes that the system shall be started in advance of the occupied time. The control moni- tors its results and adjusts the ``K'' factor to ensure that the occupied set point is achieved at time of occupancy rather than too early or too late.
ADAPTIVE OPTIMAL STOP (CV Applications Only) Ð Optimal stop is used to allow space temperature to drift to an expanded occupied set point during the last portion of an occupied period. The control calculates a stop time offset, (the time in minutes prior to the scheduled unoccupied time) during which expanded heating and cooling set points can be used. Adaptive optimal stop utilizes space temperature, an expanded occupied set point, and a ``K'' factor to calcu- late stop time offset. The amount (F) to expand the occupied
set point is user con®gurable. Like adaptive optimal start, the control corrects itself for optimal operation by adjusting the ``K'' factor as required.
GAS HEATING, OPERATION (48MP Units Only) Ð Re- fer to the Controls, Operation and Troubleshooting instruc- tions for information on the control logic used by the unit controls for gas heat operation.
The 48MPD units have 2 gas heat sections. The 48MPE units have 3 gas heat sections. Each individual section op- erates in the same manner.
NOTE: The 48MP units have 2 stages of heat.
When the PIC control calls for heating, power is sent to W on each IGC (integrated gas controller) board. An LED (light-emitting diode) on the IGC board will be on during normal operation. A check is made to ensure that the rollout switch and the limit switch are closed and the induced-draft motor is not running. The induced-draft motor is then en- ergized, and when speed is proven with the hall effect sensor on the motor, the ignition activation period begins. The burn- ers will ignite within 5 seconds.
If the burners do not light, there is a 22-second delay be- fore another 5-second attempt. If the burners still do not light, this sequence is repeated for 15 minutes. After the 15 min- utes have elapsed, if the burners have not been lit, heating is locked out. To reset the control, use the manual reset method found in the Controls Operation and Troubleshooting book.
When ignition occurs the IGC board will continue to moni- tor the condition of the rollout and limit switches, the hall effect sensor, and the ¯ame sensor.
When additional heat is required, W2 closes and initiates power to the second stage of the main gas valve. When the thermostat is satis®ed, W1 and W2 open and the gas valve closes, interrupitng the ¯ow of gas to the main burners. If the call for W1 lasted less than 1 minute, the heating cycle will not terminate until 1 minute after W1 became active.
An LED indicator is provided on the IGC to monitor op- eration. The IGC is located by removing the side panel and viewing the IGC through the view port located in the control box access panel. During normal operation, the LED is con- tinuously on. See Table 26 for error codes.
Table 26 Ð IGC Control Board LED Alarms
INDICATION | ERROR MODE |
ON | Normal Operation |
OFF | Hardware Failure |
1 FLASH | Fan ON/OFF Delay Modi®ed |
2 FLASHES | Limit Switch Fault |
3 FLASHES | Flame Sense Fault |
4 FLASHES | 4 Consecutive Limit Switch Faults |
5 FLASHES | Ignition Lockout Fault |
6 FLASHES | Induced Draft Motor Fault |
7 FLASHES | Rollout Switch Fault |
8 FLASHES | Internal Control Fault |
| |
LEGEND
IGC Ð Integrated Gas Unit Controller
LED Ð Light-Emitting diode
NOTES:
1.There is a 3-second pause between error code displays.
2.If more than one error code exists, all applicable error codes will be displayed in numerical sequence.
3.Error codes on the IGC will be lost if power to the unit is interrupted.