Table of Contents
Advertisement
BAS On/Off
The BAS is scheduling the unit via an On/Off command to the BAS ON/OFF software point. The Building
Automation System can be speaking BACnet, Modbus, or N2 and is writing to the BAS On/Off point in the
open protocol point map.
DI On/Off
A hard-wired input on the RTU-MP will command the unit to start/stop. Inputs 3, 5, 8, and 9 on plug J5
can be hard-wired to command the unit to start/stop.
NOTE Scheduling can either be controlled via the unit or the BAS, but NOT both.
Indoor Fan
The indoor fan will be turned on whenever any one of the following conditions is true:
•
It is in the occupied mode - this will be determined by its own internal occupancy schedule
•
Whenever there is a demand for cooling or heating in the unoccupied mode
•
Whenever the remote occupancy switch is closed during DI On/Off schedule type or if occupancy is
forced occupied by the BAS during BAS On/Off schedule type.
When transitioning from unoccupied to occupied, there will be a configured time delay of 5 to 600 seconds
before starting the fan. The fan will continue to run as long as compressors, heating stages, or the
dehumidification relays are on when transitioning from occupied to unoccupied, with the exception of
Shutdown mode.
If Fire Shutdown, safety chain, SAT alarm or SPT alarm are active, the fan will be shutdown immediately,
regardless of the occupancy state or demand.
The RTU-MP does not include controls/algorithms for additional building smoke-control functions such as
smoke-purge, zone-pressurization or smoke-ventilation. Each of these requires a field-designed circuit to
input the proper signals to the RTU-MP and to operate the following, as required by local fire codes:
•
de-activation of smoke alarm signal
•
RTU Indoor Fan
•
RTU economizer
•
RTU power exhaust
The RTU-MP 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 it is not enabled, then it will always be
the same state as the Supply Fan Relay. The cooling, economizer, heating, dehumidification, CO2 and power
exhaust routines will use this input point for fan status.
Cooling
The compressor outputs are controlled by the Cooling Control PID Loop and Cooling Stages Capacity
algorithm. They will be used to calculate the desired number of stages needed to satisfy the space by
comparing the Space Temperature (SPT) to the Occupied Cool Setpoint, plus the T56 slider offset, when
occupied and the Unoccupied Cool Setpoint (UCSP), plus the T56 slider offset, if unoccupied. The economizer,
if available, will be used for cooling in addition to the compressors.
The following conditions must be true in order for this algorithm to run:
•
Indoor Fan has been ON for at least 30 seconds
RTU-MP Controller
15
Advertisement
Table of Contents
