Communication Manual for
Modbus and BACnet (MSTP and IP)
Manual Revision 1.02
© 2021 Airtex Manufacturing Partnership. All rights reserved.
www.engineeredair.com
MSTP and IP Communication Manual for Modbus and BACnet
If any errors or omissions are noted please contact the nearest Engineered Air Technical Service Department. To ensure warranty is honored, only qualified personnel should be employed for service or troubleshooting. If further information is required please contact the nearest Engineered Air sales office.
Copyright
This document and the information in it are the property of Engineered Air, and may not be used or reproduced in whole or in part without written permission. Engineered Air reserves the right to revise this publication at any time, and to make changes to its content without obligation to notify any person of such revision or change.
CONTACT INFORMATION
Canadian Head Office and Factory
1401 Hastings Cres. SE
Calgary, Alberta, Canada
T2G 4C8
PH: (403) 287 2590
FX: 1 888 364 2727
Email: service@engineeredair.com
USA Head Office and Factory
32050 W. 83rd Street
De Soto, Kansas, USA
66018
PH: (913) 583 3181
FX: (913) 583 1406
Canadian Eastern Factory
1175 Twinney Drive
Newmarket, Ontario, Canada
L3Y 5V7
PH: (905) 898 1114
FX: (905) 898 7244
This Manual is designed to be used and read in conjunction with the CenCon User Manual. A digital printable copy of all manuals can be found at https://www.engineeredair.com/manuals/
The CenCon is a configurable logic controller designed to be the primary controller of Engineered Air heating, cooling and ventilation equipment. This manual should be used in conjunction with the CenCon operation manual. The CenCon is designed to control the cooling, heating, and mixing economizer. In this manual, the primary setpoint and sensor refer to the final leaving temperature. All temperature register readings are based on degrees Fahrenheit. Conversion to degrees Celsius can be accomplished at the front end software.
The CenCon is equipped with two RS485 ports equipped for Modbus RTU the BACnet® MS/TP protocols and an Ethernet port equipped for the BACnet® TCP/IP protocol. This manual describes the BACnet® objects and the information contained in each object. In this manual, BACnet® objects that can be written to are said to be EMS (Energy Management System) commanded, identified by R/W (Read/ Write).
INTRODUCTION
The CenCon supports Modbus RTU, BACnet MS/TP RS-485 and BACnet/IP. The Baud rate is fixed at 19200 for Modbus RTU networks and can be adjusted from 19200 to 38400 for MS/TP networks. This manual describes the BACnet objects and the information contained in the CenCon. In this manual object points that can be written to are said to be EMS (Energy Management System) commanded.
Wiring
The CenCon can be connected to either an RS-485 network or a to an Ethernet/IP network. The BACnet MS/TP RS-485, & BACnet/IP communication cables must conform to BACnet specifications.
RS485
The CenCon has a gray terminal strip that is used for all RS-485 communication connections.
Terminals SmA and SmB have been designated and must be used to connect to the RS-485 Modbus network terminals.
Terminals BnA and BnB have been designated and must be used to connect to the RS-485 BACnet network.
The RS-485 communication cable to the CenCon should be a 24awg shielded twisted pair (STP) with a shunt capacitance of 16pF per foot and 100 ohm characteristic impedance.
Ethernet
The CenCon is equipped with a standard RJ45 Ethernet port located on the top of the controller. The Ethernet port is designed to be incorporated with a BACnet® over IP network that is used to communicate with the building EMS.
BACnet Communication Default Factory Settings
These default settings can be configured on the CenCon service display.=
Modbus RTU
| Baud Rate | 19200 |
| Address | 1 |
BACnet MSTP
| Instance | 270000 |
| Baud Rate | 38400 |
| Address | 3 |
| Max Master | 10 |
| Max Info Frames | 20 |
BACnet IP
| Instance | 270000 |
| IP | 192.168.0.10 |
| Subnet | 255.255.255.0 |
| Gateway | 000.000.000.000 |
| DNS 1 | 000.000.000.000 |
| UDP Port# | 47808 (not adjustable) |
Note:
After making any changes to the default communication setting you must cycle the power to the controller to reset it and force the updates.
PICS & BTL Approved
BACnet PICS (Protocol Implementation Conformance Statement) defines the options available by BACnet that are implemented in the CenCon. These PICS are available from the factory upon request. The following defines the BACnet objects available on the network. EMS is used to describe the objects that can be commanded by any 3rd party ‘Energy Management System’.
CenCon POINTS LIST
Depending on the style and type of appliance, not all points will be valid.
Read / Write
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Discharge Air Setpoint | O | 40001 | AO0 | Int/10 °F | R/W |
| Damper Minimum Position | O | 40002 | AO1 | Integer mV | R/W |
| VFD Minimum Speed | O | 40003 | AO2 | Integer mV | R/W |
| Humidification Setpoint | O | 40004 | AO3 | Integer % | R/W |
| Dehumidification Setpoint | O | 40005 | AO4 | Integer % | R/W |
| Supply Fan Enable | O | 00001 | BO0 | 0/1 | R/W |
| C-XM Enable | O | 00002 | BO1 | 0/1 | R/W |
| J-XM Enable | O | 00003 | BO2 | 0/1 | R/W |
| G-XM Enable | O | 00004 | BO3 | 0/1 | R/W |
| M-XM Enable | O | 00005 | BO4 | 0/1 | R/W |
| S-XM Enable | O | 00006 | BO5 | 0/1 | R/W |
| H-XM Enable | O | 00007 | BO6 | 0/1 | R/W |
| ER-XM Enable | O | 00008 | BO7 | 0/1 | R/W |
| C-XM Dehumidification Enable | O | 00009 | BO8 | 0/1 | R/W |
Read Only
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Modulating Cooling | O | 40003 | AO2 | Integer mV | R |
| Modulating Economizer | O | 40002 | AO1 | Integer mV | R |
| Modulating Heating | O | 40001 | AO0 | Integer mV | R |
| VFD Command Speed | O | 40004 | AO3 | Integer mV | R |
| VFD Feedback Speed | I | 30007 | AI6 | Integer mV | R |
| Supply Duct Pressure | I | 30002 | AI1 | Integer | R |
| Outside Humidity | I | 30003 | AI2 | Integer % | R |
| Return/ Room Humidity | I | 30006 | AI5 | Integer % | R |
| Feedback Damper | I | 10002 | BI1 | 1/0 | R |
| Damper End Switch | I | 10005 | BI4 | I/O | R |
| Alarm | O | 00005 | BO4 | 1/0 | R |
| Supply Air | O | 00003 | BO2 | 1/0 | R |
| Damper Actuator | O | 00002 | BO1 | 1/0 | R |
| Occupied/ Unoccupied | I | 10006 | BI5 | 1/0 | R |
| Time Clock Bypass | I | 10007 | BI6 | 1/0 | R |
| Enable Fan | I | 10008 | BI7 | 1/0 | R |
| Secondary BACnet Alarm | I | 10001 | BI0 | 1/0 | R |
| Mixed Air Temperature | I | 30019 | AI18 | Int/10 °F | R |
| Discharge Air Temperature | I | 30021 | AI20 | Int/10 °F | R |
| Ambient Air Temperature | I | 30020 | AI19 | Int/10 °F | R |
| Return/ Room Temperature | I | 30017 | AI16 | Int/10 °F | R |
| Modulating Room Thermostat | I | 30009 | AI8 | Integer % | R |
| Remote VFD Setpoint | I | 30010 | AI9 | Integer % | R |
| Modulating Humidity | I | 30006 | AI5 | Integer % | R |
| DX Coil Temperature | I | 30018 | AI17 | Int/10 °F | R |
| Dehumidification | I | 10009 | BI8 | 1/0 | R |
| VFD Bypass | I | 10004 | BI3 | 1/0 | R |
| Heating Demand | O | 40005 | AO4 | Integer % | R |
| Cooling Demand | O | 40006 | AO5 | Integer % | R |
| Humidification Demand | O | 40007 | AO6 | Integer % | R |
| Recovery Demand | O | 40008 | AO7 | Integer % | R |
| Dehumidification Demand | O | 40009 | AO8 | Integer % | R |
EXPANSION MODULES POINTS LIST
The following points are read only.
C-XM
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Modulating Compressor | O | 40001 | AO0 | Integer mV | R |
| Modulating Condenser Fan #1 | O | 40002 | AO1 | Integer mV | R |
| Modulating Condenser Fan #2 | O | 40003 | AO2 | Integer mV | R |
| Modulating Reheat | I | 40004 | AO3 | Integer mV | R |
| Cooling stage #1 | O | 00001 | BO0 | 1/0 | R |
| Cooling stage #2 | O | 00002 | BO1 | 1/0 | R |
| Cooling stage #3 | O | 00003 | BO2 | 1/0 | R |
| Cooling stage #4 | O | 00004 | BO3 | 1/0 | R |
| Cooling stage #5 | O | 00005 | BO4 | 1/0 | R |
| Cooling stage #6 | O | 00006 | BO5 | 1/0 | R |
| Condenser Fan Stage #1 | O | 00007 | BO6 | 1/0 | R |
| Condenser Fan Stage #2 | O | 00008 | BO7 | 1/0 | R |
| Stepped Reheat Stage #1 | O | 00009 | BO8 | 1/0 | R |
| Stepped Reheat Stage #2 | O | 00010 | BO9 | 1/0 | R |
| Digital Output (SSR) | I | 10001 | BI1 | 1/0 | R |
| Dehumidify Setpoint | I | 30021 | AI21 | Integer % | R |
| Enable Reheat | I | 10001 | BI0 | 1/0 | R |
| Enable Cooling | I | 10002 | BI1 | 1/0 | R |
J-XM
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Feedback Gas | I | 30003 | AI2 | Integer mV | R |
| Feedback Air | I | 30004 | AI3 | Integer mV | R |
| Modulating Ball Valve | O | 40001 | AO0 | Integer mV | R |
| Combustion Air Switch | I | 10003 | BI2 | 1/0 | R |
| Blocked Flue Switch | I | 10001 | BI0 | 1/0 | R |
| Enable Heat | I | 10002 | BI1 | 1/0 | R |
| Pilot Valve | O | 00005 | BO4 | 1/0 | R |
| Safety Relay | O | 00006 | BO5 | 1/0 | R |
| Flame Relay | O | 00007 | BO6 | 1/0 | R |
| High Limit | I | 10005 | BI4 | 1/0 | R |
| Condensate Probe | I | 30005 | AI4 | Integer | R |
| MX Valve | O | 40005 | AO4 | Integer | R |
G-XM
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Feedback Gas | I | 30003 | AI2 | Integer mV | R |
| Feedback Air | I | 30004 | AI3 | Integer mV | R |
| Modulating Ball Valve | O | 40001 | AI0 | Integer mV | R |
| Modulating Combustion Air | O | 40002 | AI1 | Integer mV | R |
| Combustion Air Switch | I | 10003 | BI2 | 1/0 | R |
| Blocked Flue Switch | I | 10001 | BI0 | 1/0 | R |
| Enable Heat | I | 10002 | BI1 | 1/0 | R |
| Combustion Blower | O | 00001 | BO0 | 1/0 | R |
| Pilot Valve | O | 00005 | BO4 | 1/0 | R |
| Safety Relay | O | 00006 | BO5 | 1/0 | R |
| Flame Relay | O | 00007 | BO6 | 1/0 | R |
| High Limit | I | 10005 | BI4 | 1/0 | R |
| Condensate probe sensor | I | 30005 | AI4 | Integer Ω | R |
M-XM
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Feedback Gas | I | 30003 | AI2 | Integer mV | R |
| Modulating Ball Valve | O | 40001 | AO0 | Integer mV | R |
| Profile Pressure Actuator | O | 40002 | AO1 | Integer mV | R |
| High Speed Enable | I | 10001 | BI0 | 1/0 | R |
| Enable Heat | I | 10002 | BI1 | 1/0 | R |
| High Speed | O | 00001 | BO0 | 1/0 | R |
| Exhaust Fan Interlock | O | 00002 | BO1 | 1/0 | R |
| Dual Flame Rod | O | 00003 | BO2 | 1/0 | R |
| Water Pump | O | 00004 | BO3 | 1/0 | R |
| Pilot Valve | O | 00005 | BO4 | 1/0 | R |
| Safety Relay | O | 00006 | BO5 | 1/0 | R |
| Flame Relay | O | 00007 | BO6 | 1/0 | R |
| High Limit | I | 10005 | BI4 | 1/0 | R |
| MX Valve | O | 40005 | AO4 | Integer | R |
ER-XM
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Modulating By-Pass Damper | O | 40001 | AO0 | Integer mV | R |
| Modulating Energy Recovery | O | 40002 | AO1 | Integer mV | R |
| Enable Heat | I | 10001 | BI0 | 1/0 | R |
| Rotation Sensor | I | 10002 | BI1 | 1/0 | R |
| By-Pass Damper | O | 00001 | BO0 | 1/0 | R |
| Enable Wheel | O | 00005 | BO4 | 1/0 | R |
| Leaving Air Temperature | I | 30020 | AI19 | Int/10 °F | R |
| Exhaust Air Temperature | I | 30021 | AI20 | Int/10 °F | R |
S-XM
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Feedback Gas | I | 30003 | AI2 | Integer mV | R |
| Modulating High Limit | I | 30004 | AI3 | Integer mV | R |
| Modulating Ball Valve | O | 40001 | AO0 | Integer mV | R |
| Duct High Limit | I | 10003 | BI2 | 1/0 | R |
| Blocked Flue Switch | I | 10001 | BI0 | 1/0 | R |
| Enable Heat | I | 10002 | BI1 | 1/0 | R |
| Fill Valve | O | 00001 | BO0 | 1/0 | R |
| Mixing Valve | O | 00002 | BO1 | 1/0 | R |
| Drain Valve | O | 00003 | BO2 | 1/0 | R |
| Fill Valve Side | O | 00004 | BO3 | 1/0 | R |
| Pilot Valve | O | 00005 | BO4 | 1/0 | R |
| Safety Relay | O | 00006 | BO5 | 1/0 | R |
| Flame Relay | O | 00007 | BO6 | 1/0 | R |
| High Limit | I | 10005 | BI4 | 1/0 | R |
| Direct Humidity Control | I | 30001 | AI0 | Integer | R |
| Drain Sensor | I | 30016 | AI15 | Integer Ω | R |
| Condensate Probe | I | 30005 | AI4 | Integer Ω | R |
| Fill Water Probe | I | 30007 | AI6 | Integer Ω | R |
| Low Water Probe | I | 30006 | AI5 | Integer Ω | R |
| MX Valve | O | 40005 | AO4 | Integer | R |
H-XM
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Modulating Output | O | 40002 | AO1 | Integer mV | R |
| Enable Heat | I | 10001 | BI0 | 1/0 | R |
| Heating Stage #1 | O | 00001 | BO0 | 1/0 | R |
| Heating Stage #2 | O | 00002 | BO1 | 1/0 | R |
| Heating Stage #3 | O | 00003 | BO2 | 1/0 | R |
| Heating Stage #4 | O | 00004 | BO3 | 1/0 | R |
| Heating Stage #5 | O | 00005 | BO4 | 1/0 | R |
| Heating Stage #6 | O | 00006 | BO5 | 1/0 | R |
| Heating Stage #7 | O | 00007 | BO6 | 1/0 | R |
| Door Switch | I | 10004 | BI3 | 1/0 | R |
| High Limit | I | 10005 | BI4 | 1/0 | R |
CD-XM
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Combustion Blower | O | 00001 | BO0 | 1/0 | R |
| Safety Relay | O | 00002 | BO1 | 1/0 | R |
P-XM
| DESCRIPTION | In / Out | MODBUS Register |
BACnet Address |
TYPE | R/W |
| Pressure Switch | O | 00002 | BO1 | 1/0 | R |
| Pressure Sensor | O | 30001 | AI0 | Integer “wc | R |
| Pressure Transducer | O | 40001 | AO0 | Integer mV | R |
POINT DESCRIPTIONS
Read / Write
The following Software point list are commandable (Read/Write) by BACnet or Modbus. Available points depend on appliance type and arrangement.
Discharge Air Setpoint
Final calculated discharge setpoint.
Damper Minimum Position Setpoint
Minimum outside air setpoint.
VFD Minimum Speed Setpoint
VFD minimum speed setpoint; Refer to unit function for requirements.
Humidification Setpoint
Room or return air humidity setpoint.
Dehumidification Setpoint
Room or return air dehumidification setpoint.
Supply Fan Enable
Enable start for system operation.
Read Only
CenCon
Modulating Cooling
Chilled water coil valve actuator.
Modulating Economizer
Modulating economizer / mix box actuator.
Modulating Heating
Hot water coil valve actuator.
VFD Command Speed
VFD control signal.
VFD Feedback Speed
Confirmation of VFD speed.
Supply Duct Pressure
Duct pressure sensor.
C-XM Enable
Mechanical cooling expansion module.
J-XM Enable
Indirect fired gas heating expansion module for DJS, DJE, DJX (up to 140) appliances.
G-XM Enable
Indirect fired gas heating expansion module for DG anDJX 200/300 appliances.
M-XM Enable
Direct fired gas heating expansion module.
S-XM Enable
Gas fired humidifier expansion module.
H-XM Enable
Electric heat expansion module.
ER-XM Enable
HRW heat wheel energy recovery enabled.
C-XM Dehumidification Enable
Mechanical cooling with reheat appliances.
Outside Humidity
Outside / ambient air relative humidity sensor.
Return/ Room Humidity
Room / return air relative humidity sensor.
Feedback Damper
Economizer / mix box damper actuator position feedback signal.
Damper End Switch
Mechanical damper end switch.
Alarm
General alarm output annunciation.
Supply Air
Blower enable status.
Damper Actuator
Damper actuator status.
Occupied/ Unoccupied
Enable occupied mode
Enable Fan
Appliance enable.
Secondary BACnet Alarm
Spare alarm input for BACnet annunciation
Mixed Air Temperature
Economizer or mixing damper leaving air temperature.
Discharge Air Temperature
Final leaving temperature.
Ambient Air Temperature
Ambient/outside air temperature.
Return/ Room Temperature
Return or room air temperature.
Modulating Thermostat
Roomstat heating / cooling signal.
Remote VFD Setpoint
VFD speed demand signal.
Modulating Humidity
Humidity demand signal.
DX Coil Temperature
Pre-cool leaving air temperature.
Dehumidification
Dehumidification mode enabled.
VFD Bypass
VFD bypass mode active.
C-XM
Modulating Compressor
Output to modulating compressor.
Modulating Condenser Fan #1 & #2
Output to variable speed condenser fans.
Modulating Reheat
Output to modulating hot gas reheat coil.
Cooling stage #1 to #6
Cooling stages enabled.
Condenser Fan Stage #1 & #2
Ambient temperature based condenser fan #1 or #2 enabled.
Stepped Reheat Stage #1 & #2
Stepped / staged reheat output.
Dehumidify Setpoint
RH% setpoint for dehumidification operation.
Enable Reheat
Hot gas reheat enabled.
Enable Cooling
Mechanical cooling enabled.
J-XM
Feedback Gas
Modulating gas valve actuator feedback signal.
Modulating Ball Valve
Modulating gas valve actuator output.
Combustion Air Switch
Proof of combustion air flow.
Blocked Flue Switch
Opens on blocked flue.
Enable Heat
Expansion module heating function enabled.
Pilot Valve
Pilot valve operation is interrupted once main flame sensing is established.
Safety Relay
Secondary safety lockout contact.
Flame Relay
Flame relay contact enabled.
High Limit
Opens on high heat exchanger section temperature.
Condensate Probe
Condensate probe sensor (Ω).
MX Valve
DC current output to the magnetic style modulating gas valve.
G-XM
Feedback Gas
Modulating gas valve actuator feedback signal.
Feedback Air
Modulating combustion air actuator feedback signal.
Modulating Ball Valve
Modulating gas valve actuator output.
Combustion Air Switch
Proof of combustion air flow.
Blocked Flue Switch
Normally closed, opens on blocked flue.
Enable Heat
Expansion module heating function enabled.
Pilot Valve
Pilot valve operation is interrupted once main flame sensing is established.
Safety Relay
Secondary safety lockout.
Flame Relay
Flame relay enabled.
High Limit
Normally closed, opens on high temperature
Condensate Probe
Condensate probe sensor
M-XM
Feedback Gas
Modulating gas valve actuator feedback signal.
Modulating Ball Valve
Modulating gas valve actuator output.
Profile Pressure
Modulating profile pressure damper actuator position.
High Speed Enable
Initiate high speed operation.
Enable Heat
Expansion module heating function enabled.
High Speed
High speed fan start contact.
Exhaust Fan Interlock
Single or low speed exhaust fan start contact.
Dual Flame Rod
Relay output to switch flame rods.
Water Pump
Enable evaporative (swamp cooler) water pump.
Pilot Valve
Pilot valve operation is interrupted once main flame sensing is established.
Safety Relay
Secondary safety lockout contacts.
Flame Relay
Flame relay enable contacts.
High Limit
Normally closed, opens on high temperature.
MX Valve
DC current output to the modulating gas valve.
ER-XM
Modulating By-Pass Damper
Modulating output to bypass damper actuator.
Modulating Energy Recovery
Modulating output to heat wheel drive motor, heat pipe tilt actuator, or heat plate damper actuator.
Enable Heat
Expansion module energy recovery operation.
Rotation Sensor
Input from rotation sensor.
By-Pass Damper
Bypass damper enabled.
Enable Wheel
Wheel motor start enabled.
Leaving Air Temperature
Temperature of the air at heat recovery device’s discharge plenum, in ⁰F
Exhaust Air Temperature
Temperature of the air at heat recovery device’s exhaust plenum, in ⁰F
S-XM
Feedback Gas
Compares the ball valve actuator feedback signal to the demand signal.
Modulating High Limit
Optional analog input for duct mounted high humidity sensing.
Modulating Ball Valve
Modulating gas valve actuator output.
Duct High Limit
Duct mounted high humidity sensing opens on high humidity.
Blocked Flue Switch
Normally closed, opens on blocked flue.
Enable Heat
Gas fired humidifier expansion module enabled.
Fill Valve
Enable side tank (SHX) fill valve.
Pilot Valve
Pilot valve operation is interrupted once main flame sensing is established.
Safety Relay
Secondary safety lockout contacts.
Flame Relay
Flame relay enable contacts.
High Limit
Normally closed, opens on high temperature.
Direct Humidity
Input for direct control of humidifier.
Drain Sensor
Drain probe sensor input.
Condensate Probe
Condensate probe (SHX) sensor input.
Fill Water Probe
Fill water level sensor.
Low Water Probe
Low water level sensor.
MX Valve
DC current output to the modulating gas valve.
H-XM
Modulating Output
Modulating output to external SCR controller.
Enable Heat
Expansion module electric heating enabled.
Heating Stage #1 to #7
Staged heating output.
Door Switch
External safeties input
High Limit
Normally closed, opens on high temperature
CD-XM
Combustion Blower
Modulating output command to combustion air blower motor.
Safety Relay
Contact open on failure.
P-XM
Pressure Switch
Output contact.
Pressure Sensor
Pressure sensor output 0-4”w.c.
Pressure transducer
Pressure transducer scaled output from 0 to 10 VDC based on 0-4 “wc.
IOM65
August 2021 R2
Documents / Resources
 |
CenCon MSTP and IP Communication Manual for Modbus and BACnet [pdf] User Guide MSTP and IP Communication Manual for Modbus and BACnet, MSTP and IP, Communication Manual for Modbus and BACnet |
