48TC
Indoor Fan — The indoor fan will be turned on whenever any one of the following conditions are met:
SIf the PremierLink controller is in the occupied mode and ASHRAE 90.1 Supply Fan is configured for Yes in the CONFIG table. This will be determined by its own internal occupancy schedule if it is programmed to follow its local schedule or broadcast its local schedule as a global schedule, or following a global schedule broadcast by another device.
S If PremierLink controller is in the occupied mode and ASHRAE 90.1 Supply Fan is configured for No and there is a heat or cool demand (fan auto mode)
SIf the PremierLink controller is in the occupied mode and ASHRAE 90.1 Supply Fan is configured for Yes when Linkage is active and the Linkage Coordinator device is sending an occupied mode flag
S When Temperature Compensated Start is active S When Free Cool is active
SWhen
SWhenever there is a demand for cooling or heating in the unoccupied mode
S Whenever the Remote Contact input is configured for Remote Contact (RC_DC=1 in SERVICE table) and it is closed or the point is forced Closed via communications in the STATUS01 points display table (remote contact closed = occupied, remote contact open = unoccupied)
S Whenever the H3_EX_RV point is configured for Dehumidification (AUXOUT=5 in CONFIG table) and it is in the unoccupied mode and the indoor RH exceeds the unoccupied humidity setpoint
SWhenever the Supply Fan Relay point is forced On in the STATUS01 points display table
The fan will also continue to run as long as compressors are on when transitioning from occupied to unoccupied with the exception of Fire Shutdown mode. If the Fire Shutdown input point is closed or forced in the STATUS01 points display table, the fan will be shutdown immediately regardless of the occupancy state or demand.
The PremierLink controller has an optional Supply Fan Status input to provide proof of airflow. If this is enabled, the point will look for a contact closure whenever the Supply Fan Relay is on. If the input is not enabled, then it will always be the same state as the Supply Fan Relay. The cooling, economizer and heating routines will use this input point for fan status.
Cooling — The compressors are controlled by the Cooling Control Loop that is used to calculate the desired SAT needed to satisfy the space. It will compare the SPT to the Occupied Cool Setpoint (OCSP) + the T56 slider offset (STO) when occupied and the Unoccupied Cool Setpoint (UCSP + Unoccupied Cooling Deadband) if unoccupied to calculate a Cooling Submaster Reference (CCSR) that is then used by the staging algorithm (Cooling submaster loop) to calculate the required number of cooling stages. The economizer, if available, will be used as the first stage of cooling in addition to the compressors. This loop runs every minute. The following conditions must be met in order for this algorithm to run:
S indoor fan has been ON for at least 30 seconds
S heat mode is not active and the time guard between modes equals zero.
S mode is occupied or the Temperature Compensated Start or Cool mode is active
S SPT reading is available and > (OCSP + STO)
S If mode is unoccupied and the SPT > (UCSP + Unoccupied Cooling Deadband). The indoor fan will be turned on by the staging algorithm.
S OAT > DXLOCK or OAT DX Lockout is disabled
If all of the above conditions are met, the CCSR will be calculated, otherwise it is set to its maximum value and DX stages is set to 0. If only the last condition is not true and an economizer is available, it will be used to cool the space.
The submaster loop uses the CCSR compared to the actual SAT to determine the required number of capacity stages to satisfy the load. There is a programmable minimum internal time delay of 3 to 5 minutes on and 2 to 5 minutes off for the compressors to prevent short cycling. There is also a
ademand for cooling. An internal 5 to
Table 30 indicates the number of stages available. The staging algorithm looks at the number of stages available based the number of cool stages configured in the SERVICE configuration table. The algorithm will skip the economizer if it is not available and turn on a compressor.
78
