SEQUENCE OF OPERATION
IPAK SPACE TEMPERATURE CONFIGURATION
HOT GAS REHEAT PACKAGE ROOFTOP UNIT:
A. SPACE TEMP OCCUPIED CONTROL ((MP581, UC400 or UC600)):
Control of the Trane Hot Gas Reheat DX rooftop unit is accomplished through a dedicated standalone control module (MP581, UC400 or UC600). One controller will be installed on each rooftop unit (RTU). This controller utilizes five temperature sensors. The function of this controller is to maintain a programmed space air temperature.
The first temperature sensor (DXSUPPLY) is mounted after the DX evaporator coil. This temperature sensor will be used by the (MP581, UC400 or UC600) to control the compressors to maintain a 55 degree (programmable) dry bulb temperature setpoint. The controller outputs a 0-5 VDC signal (AO-2) to the GBAS board on the Intellipack Microprocessor to control discharge air setpoint.
The next temperature sensor (ZONETEMP) is field mounted in the space and will be used by the controller to enable the cooling or heating mode. In the cooling mode the (DXSUPPLY) sensor is sending a signal to the Intellipack controller as per the above paragraph. Once temperature setpoint is reached an analog signal is sent to the face & bypass damper actuator (FBDAMPER) to modulate free condenser heat into the airstream to maintain the space temperature setpoint. The space temperature is adjustable based on the sensor setpoint dial input (IN-6). After a 3 degree deadband heating is enabled.
Four strap-on temperature sensors will be used in the Intellipack Microprocessor. Strap-on temperature sensor #1 and 2 will be located in the suction line. These temperature sensors will disable both cooling circuits when the temperature goes below 32 degrees and enable them above 38. Strap-on temperature sensor #3 and 4 will be located on the condenser coil. These temperature sensors will enable control of condenser fans by the Intellipack controller to maintain head pressure.
The last temperature sensor (OASUPPLY) is mounted in the condenser section and monitors the outdoor air temperature.
When heating is called for (based on the ZONETEMP temperature), the (MP581, UC400 or UC600) will go into heating mode and the heating will be brought on as required to maintain the ZONETEMP heating setpoint (programmable).
The actual output signal for the heat control will operate based on the type of heat the unit has.
If the unit has electric style heat then the following will occur:
The electric heat is controlled by an analog signal (AO3) from the (MP581, UC400 or UC600). The analog signal (AO3) heat sequencer will modulate to open and close the contactors of the electric stages of heat.
If the unit has SCR style heat then the following will occur:
The SCR is controlled by an analog signal (AO3) from the (MP581, UC400 or UC600). The SCR controller modulates the electric heater based on the heating setpoint. On a multiple stage heater the SCR controls the first stage. Once the SCR ramps up to 100% another analog signal (AO4) heat sequencer will then modulate to open and close the contactors of other stages of heat.
If the unit has hot water style heat then the following will occur:
An analog output (AO3) from the (MP581, UC400 or UC600) will modulate the heating valve with a 0-10VDC signal
If the unit has gas style heat then the following will occur:
An analog output (AO3) from the (MP581, UC400 or UC600) will modulate the signal to the heating setpoint of the GBAS with a 0-5 VDC signal
**** ALL ELECTRIC TYPE HEAT SHALL BE INTERLOCKED THROUGH THE AUXILLERY CONTACTS OF THE FAN CONTACTOR (IN ADDITION TO THE OTHER SAFTIES) TO PREVENT THE HEAT FROM BEING ENERGISED WITHOUT THE FAN BEING CALLED FOR.
The (MP581, UC400 or UC600) is programmed to maintain the space temperature setpoint (for heating and cooling). Low and High limits of 68 and 76 are programmed for cooling and heating respectively. The controller has all of these functions pre-programmed, however since it is fully programmable, the setpoints and sequence can be modified if required.
B. FAN PROVING DEVICE:
A contact closure into the (MP581, UC400 or UC600) IN-8 will indicate to the controller proof of airflow from a differential pressure switch allowing either cooling or heating to operate.
C. OCCUPIED/UNOCCUPIED CONTROL:
A contact closure into the (MP581, UC400 or UC600) IN-7 will indicate to the controller an occupied mode of operation (the controller will operate in the unoccupied mode while the contacts into IN-7 are open). The dry contact input will be wired from either a time clock or the building energy management system.
D. UNOCCUPIED MODE:
When the (MP581, UC400 or UC600) is indexed to the unoccupied mode, the supply fan will be OFF and the cooling and heating stages will be OFF. An unoccupied setpoint can be programmed in the controller to bring on the supply fan and cooling and/or heating to a setback temperature.
E. RTU SHUTDOWN CONTROL:
A dry contact opening across terminals 17 and 18 on the external auto stop (TB4) will put the RTU in a fire shutdown mode of operation (contact by others).
F. SETPOINT SELECTION:
The setpoints for unit operation will be selected based on a priority level that will seek communications with various devices to determine the correct set of setpoints to be used. The (MP581, UC400 or UC600) will search 1st for a LONTALK or BACnet device. If no such network server is found or if the communication to that device has been lost, then the controller will try to control to setpoints that are being sent from a Tracer Summit BCU (Building Control Unit). If a Tracer Summit system is not located or has lost its communication to the controller, then the controller will default to its own “Local” setpoints. These setpoints are embedded in the software that is loaded at the factory and can only be accessed from Trane “ROVER” software/hardware or if the controller has a display connected to the controller.
Setpoints and their defaults:
76 deg. = Thumbwheel High Limit
68 deg. = Thumbwheel Low Limit
3 deg. = Zone Temperature Deadband
3 % = Heating Deadband
63 deg. = DX Setpoint HIGH Limit