ECC-PCP Modbus RTU BAS Interface SUPERSEDES: none FORM NO: SVW06-ModbusIG-20150209 ECC-PCP Modbus RTU BAS Interface Guide Introduction PoolComPak units equipped with the ECC-PCP controller can be directly connected to a Modbus based Building Automation System (BAS). Specifically, the protocol is Modbus RTU using an RS485 physical layer with the ECC-PCP acting as a slave device. The device address and baud rate can be configured in the field. 25 control points that include all basic information and set points for the PoolComPak dehumidification system are available through the interface. Modbus Protocol Details The protocol used by the ECC-PCP is Modbus RTU with 8 bit encoding and 16 bit CRC error checking. The ECC-PCP operates as a slave on the Modbus network. Modbus protocol implementation complies with the document: Modicon Modbus Protocol Reference Guide March 1992, PI-MBUS-300 Rev. D This document is available from the web site www.modbus.org. The communications port on the ECC-PCP is an optically isolated RS485 transceiver. Port settings are: 8 data bits, 2 stop bits, and no parity. The baud rate can be field adjusted from 1200 up to 19200 by setting a configuration parameter in the ECC-PCP service menu. The following Modbus functions are implemented in the ECC-PCP: Function Code Function Description 01 Read Output Status Read digital variables 02 Read Input Status Read digital variables 03 Read Output Registers Read analog/integer variables 04 Read Input Registers Read analog / integer variables 05 Force Single Coil Write digital variable 06 Force Single Register Write analog / integer variable 15 Force Multiple Coils Write multiple digital variables 16 Preset Multiple Registers Write multiple analog / integer variables
The error messages returned by the ECC-PCP conform to the Modbus specification. Specifically, when an error occurs, the packet sent back to the master contains the original function code with the most significant bit set to 1, followed by a byte containing the error code number. The following Modbus error codes are implemented in the ECC-PCP: Error Code Description 01 Illegal Function 02 Illegal Data Address 03 Illegal Data Value If the ECC-PCP receives a packet with an incorrect check sum, no error message will be returned to the master. If the master requests a register value that does not exist in the ECC-PCP, the value will be returned as 0. ECC-PCP Modbus Configuration Parameters The Modbus configuration parameters for the controller are accessed in the Service menu. To configure these parameters: 1. Press the Program key ( ) the controller or RIU. 2. Use the arrow keys to scroll down to Service and press Enter ( ). 3. Enter the service password 0005. 4. Use the arrows keys to scroll down to the Unit Config menu and then press Enter ( ). 5. Enter the factory password 9995. 6. Use the arrow keys to scroll to the Installed Options menu then press Enter ( ). 7. Use the arrow keys to scroll to the parameter LonWorks Board. Change this to NO then press Enter ( ). 8. Press Escape key ( ) one time then scroll to BAS Interface menu, press Enter ( ). 9. If the settings of the parameters differ from those shown below, press Enter ( ) to move the cursor down next to the parameter, then use the arrow keys to change to the correct Type Modbus Selects the type of BAS interface. Baudrate This parameter sets the baud rate for the onboard serial port. It can be set to 1200, 2400, 4800, 9600, or 19200. The factory default setting is 9600. BAS Addr 1 This parameter sets the address of the ECC-PCP on the Modbus network. It can be set to any integer from 1 to 247. 10. After changing any of these parameters, the controller should be rebooted by cycling power to the dehumidifier. 2 of 5
Physical Network Connection The terminal blocks for field connection to the Modbus RTU network are located on the main control module in the PoolComPak unit s control panel. The block is labeled Serial Card. Terminals A, B, and GND are used for connection to the network with the following functions: Terminal ID Function B or - Tx/Rx - A or + Tx/Rx + GND Ground PoolPak recommends the use of 22 AWG shielded twisted pair cable for runs up to 500 feet. For runs greater than 500 feet, contact the factory. Use two wires from the same pair for connection of A and B. Use both wires from a second pair for connection of GND. Control Points Mapping The Modbus interface provides 25 control points that include all basic status information and set points for the PoolComPak dehumidification system. There are three types of points available, analog, integer, and digital. Analog values are multiplied by 10 before being sent through the Modbus interface. For example, a return air temperature of 25.3 will be sent through the Modbus interface as 253. Integer and digital values are sent directly through the interface without modification. The following table lists the available points along with their address offsets and types. For more information on the use of address offsets, please refer to the Modicon standard referenced on page 1 of this document. Note: Temperatures are expressed in degrees Celsius. Temperature set points are expressed in degrees Fahrenheit. Address Offset Description Point Type Var Type 2 Return Air Temperature Input Register (3XXXX) Analog 3 Outside Air Temperature Input Register (3XXXX) Analog 4 Cold Surface Temperature Input Register (3XXXX) Analog 5 Return Air Relative Humidity Input Register (3XXXX) Analog 6 Pool Water Temperature Input Register (3XXXX) Analog 130 Active Fault Code Input Register (3XXXX) Integer 131 Fault Count Input Register (3XXXX) Integer 132 Return Air Temperature Set Point Input Register (3XXXX) Integer 133 Pool Water Temp Set Point Input Register (3XXXX) Integer 134 Return Air RH Set Point Input Register (3XXXX) Integer 135 Return Air Temperature Set Point Holding Reg. (4XXXX) Integer 3 of 5
Active Fault Code 136 Pool Water Temp Set Point Holding Reg. (4XXXX) Integer 137 Return Air RH Set Point Holding Reg. (4XXXX) Integer 2 Purge Mode Status Input Status (1XXXX) Digital 3 AC Proof Status Input Status (1XXXX) Digital 4 Pool Heating Status Input Status (1XXXX) Digital 5 Aux Pool Heating Status Input Status (1XXXX) Digital 6 Dehumidification Status Input Status (1XXXX) Digital 7 Air Heating Status Input Status (1XXXX) Digital 8 Air Cooling Status Input Status (1XXXX) Digital 9 Aux Air Heat Stage 1 Status Input Status (1XXXX) Digital 10 Aux Air Heat Stage 2 Status Input Status (1XXXX) Digital 11 Force Purge Mode Coil Status (0XXXX) Digital 12 Force No Purge Mode Coil Status (0XXXX) Digital 13 Active Alarm Present Coil Status (0XXXX) Digital The active fault code is an integer with values as follows: 0 All systems normal. 1 System in OFF mode. (Aux Water Heating System still enabled) 2 System startup active. 4 Fan motor overload is tripped. 5 Fire trip is active. 7 Space temperature is out of normal range. (70 F < Normal < 105 F) 12 Defrost mode active. 13 Low refrigerant pressure. 14 High compressor motor temperature. 15 High refrigerant pressure. 16 Space temperature sensor failed. 17 Space relative humidity sensor failed. 18 Pool water temperature sensor failed. 19 Outside air temperature sensor failed. 20 Surface temperature sensor failed. 21 Controller failed self diagnostic test. 22 Compressor locked out after ten faults. Changing a Set Point Two data points are allocated for each set point. One of the points is a holding register and the other is an input register. To change a set point, use function code 6 to force the appropriate holding register to the new set point Verify that the ECC-PCP has accepted the new value by reading the value back from the corresponding input register. There are value limits for each set point. If the BAS tries to set an inappropriate value, the ECC-PCP will apply the limits to the 4 of 5
requested change. The BAS can detect this event by verifying the change in the input register for the set point. Controlling Occupied and Purge Modes The BAS can control the PoolComPak unit s Purge Mode directly. This control overrides all internal control in the TD-2500 or TD-3000. To force purge mode, use function code 5 to force the coil at offset 11 to 1 and the coil at offset 12 to 0. To force no purge mode, force the coil at offset 11 to 0 and the coil at offset 12 to 1. Active Alarm Flag Control The coil at offset 13 indicates the status of the ECC-PCP alarm flag. This status corresponds to the red light inside the RIU s alarm button. When the status is 1, there is an uncleared alarm present in the ECC-PCP. To clear the alarm, use function code 5 to force the coil at offset 13 to 0. If there are no active alarms in the system, the coil value will stay 0. If there are still active alarms present, the ECC-PCP will set the coil value back to 1. Troubleshooting Symptom Possible Cause Solution No response from ECC- PCP when polled by the master on the Modbus network Set point changes are different than requested by BAS. Replies from ECC-PCP are sporadic. Power to ECC-PCP is off. Incorrect baud rate setting. Incorrect BAS Address setting. Incorrect Serial Port Protocol setting. Serial port polarity is reversed. Requested set point value is outside of the acceptable range. Electrical interference. Turn on power to ECC- PCP at PoolComPak control panel. Set the baud rate parameter to the correct Set the BAS Address parameter to the correct Set the Serial Port Protocol parameter to MBRTU. Swap the wires connected to A and B. Select set points based on the acceptable range. Route network wiring away from other electrical devices. Modbus is a registered trademark of Schneider Electric USA, Inc. Corporation. This trademark is used in the text. However, for the sake of readability, they may not be individually marked. 5 of 5