Lochinvar SYNC SB 1000 User manual

SYNC-MODB Rev A
This manual must only be used by a
qualified heating installer / service
technician. Read all instructions,
including this manual, the
Installation and Operation Manual,
and the Service Manual, before
installing. Perform steps in the
order given. Failure to comply could
result in severe personal injury,
death, or substantial property
damage.
WARNING
Save this manual for future reference.
MODBUS COMMUNICATION
INSTRUCTIONS
SYNC Models: 1.0 - 1.3 - 1.5

2
1 Introduction
The information contained in this manual provides general guidelines for the implementation of Modbus communication with
the Lochinvar SYNC boiler.
All Modbus networks are implemented utilizing a master-slave arrangement where all SYNC boilers are slaves and the master is
a building automation system capable of communicating over a RS-485 serial connection.
Contents
1. INTRODUCTION
Definitions .................................................................... 2
Minimum System Requirements .................................. 2
2. CONFIGURATION
Addressing ................................................................... 3
Timing Specifications ................................................... 4
Parity ............................................................................ 4
Data Transmission Mode ............................................. 4
Modbus Board Diagnostics .......................................... 4
Internal Faults ......................................................... 4
Modbus Function Set.............................................. 5
Modbus Exception Codes ............................................ 6
3. MEMORY MAP
Primary Data Tables.....................................................7
SYNC Boiler Memory Map...........................................7-8
Input Registers .......................................................8
Holding Registers ...................................................8
Configuration Bits.........................................................8
4. WIRING REQUIREMENTS
Physical Wiring.............................................................9
Typical Boiler System Wiring...................................12-13
5. UNIT OPERATION
Unit Operation with Modbus Communications........ 14-17
6. TROUBLESHOOTING ........................................... 18-19
7. DIAGRAMS
Ladder Diagram Part 1 & 2..................................... 20-21
Wiring Diagram............................................................ 22
Revision Notes ................................................... Back Cover
Abbreviation or Acronym Meaning
ASCII American Standard Code for Information Interchange
BAS Building Automation System
Baud (Baud Rate) Number of data bits transmitted per second (bps)
EMS Energy Management System
FDX Full-Duplex
HDX Half-Duplex
Hex Hexadecimal Number (0 - 9, A - F)
I/O Box Input/Output (I/O)
LSB Least Significant Byte
Modbus® A serial, half-duplex data transmission protocol developed by AEG Modicon
MSB Most Significant Byte
RS232 A standard for serial, full-duplex (FDX) transmission of data based on the
RS232 Standard
RS485 A standard for serial transmission of data based on the RS-485 Standard
RTU Remote Terminal Unit
Definitions
Minimum System Requirements
• BAS system or computer with a serial or USB port with a converter to RS-485.
• SYNC boiler equipped with Modbus communication board.
• Shielded twisted pair communication cable.

3
2 Configuration
Addressing
The Modbus addressing space is comprised of 256 different
addresss.
• 0 is reserved for broadcast messages from the master
device
• 1 - 247 are free to use for each unique device
• 248 - 255 are reserved
To set the Modbus address the dip switches can be set in
either the 0 position or the 1 position. For switches set to the
1 position their value will be added together to determine the
address.
For each switch set to the 1 position it has the following value:
Dip switch 1 = 1
Dip switch 2 = 2
Dip switch 3 = 4
Dip switch 4 = 8
Dip switch 5 = 16
Dip switch 6 = 32
Dip switch 7 = 64
Dip switch 8 = 128
Any dip switch set to 0 has a value equal to 0.
Example:
To set the address of the Modbus board to 50, dip switches 2, 5,
and 6 have to be set to the 1 position. The address is determined
by adding the values of all the dip switches together.
Address = Value of Dip switch 1 + Value of Dip switch 2 + Value
of Dip switch 3 + Value of Dip switch 4 + Value of Dip switch 5
+ Value of Dip switch 6 + Value of Dip switch 7 + Value of Dip
switch 8
In this example:
Address = 0 + 2 + 0 + 0 + 16 + 32 + 0 + 0 = 50
Modbus Instructions
The Modbus communication board is equipped with a set of ten dip switches that are used to set the board configuration
(address, baud rate, and parity settings). The first eight are used to set the address of each board. The ninth baud rate. The tenth
is parity.
LED’S
DIP SWITCHES
Figure 2-1_Modbus Communication Board

4
Modbus Instructions
2 Configuration
Timing Specifications
The baud rate for the Modbus board is selectable with Dip
switch #9.
1 = 19200 bps
0 = 9600 bps
Each message is started by at least 3.5 character times of
silence. The maximum delay between frames is 1.5 character
times.
When the system temperature and/or tank temperature is
provided by the BAS to the boiler, it is critical that the
temperature be updated every few seconds. If the boiler does
not receive updated temperatures within a timeout period
(installer adjustable), the control will revert to using its own
sensor inputs (if sensors are connected). The timeout is
programmable by pressing the MAIN>>SETUP>>BMS
buttons. The timeout is adjustable between 5 and 120
seconds. The default timeout is 10 seconds.
When the BAS is not providing either of these temperatures,
but is still controlling the boiler (such as providing a
modulation command), the BAS must refresh these
commands at least every 4 minutes. If the commands are not
refreshed, the boiler will revert to operating based on its own
inputs.
Parity
Parity is set by the position of Dip switch #10.
0 = No Parity
1 = Odd Parity
If No Parity is selected there will be two stop bits, otherwise
there will be one.
Data Transmission Mode
Many Modbus bus master devices can be configured to transmit
data in either Modbus RTU or Modbus ASCII modes. Since
RTU messages can be formatted to use fewer data bits and are
therefore more efficient, RTU has been chosen to be used with
all Lochinvar Modbus communication. Please ensure that the
master device is transmitting Modbus RTU.
Modbus Board Diagnostics
The Modbus board is equipped with three LED’s for visual
diagnostics: Two yellow LED’s and one green. One yellow LED
(D5) is used to indicate reception of data. The other yellow
LED (D6) is used to indicate transmission of data. The green
LED (D7) is used to show internal faults.
Internal Faults:
Normal Operation = 1 second on, 1 second off
Controller Fault = Continuously on
No Burner Control Communication = 0.5 seconds on, 1.5
seconds off
No Modbus Communication = 1.5 seconds on, 0.5 seconds
off
Modbus Communication
The Modbus communication commands and exception codes
that are supported by the Modbus communication board can
be found on pages 5 and 6 of this manual.

5
2 Configuration (continued)
Modbus Instructions
Function Sub Function HEX Description
Dec HEX Dec
1 01 Read Coil Status
2 02 Read Input Status
3 03 Read Holding Registers
4 04 Read Input Registers
5 05 Force Single Coil
6 06 Preset Single Register
7 07 Read Exception Status
8 08 0 00 Diagnostic - Return Query Data
1 01 Diagnostic - Restart Communication
2 02 Diagnostic - Return Diagnostic Register
4 04 Diagnostic - Force Listen Mode
10 0A Diagnostic - Clear Counters and Diagnostic
Registers
11 0B Diagnostic - Return Bus Message Count
12 0C Diagnostic - Bus Communication Error Count
13 0D Diagnostic - Bus Exception Error Count
14 0E Diagnostic - Return Slave Message Count
15 0F Diagnostic - Return Communication Error Count
16 10 Diagnostic - Return Slave NAK Count
17 11 Diagnostic - Return Slave Busy Count
18 12 Diagnostic - Return Bus Character Overrun Count
20 14 Diagnostic - Clear Overrun Counter and Flag
11 0B Get Communication Event Counter
12 0C Get Communication Event Log
15 0F Write Multiple Coils
16 10 Write Multiple Registers
17 11 Report Slave ID
23 17 Read / Write Multiple Registers
Modbus Function Set

6
Modbus Instructions
2 Configuration
MODBUS Exception Codes
Code Name Meaning
01 ILLEGAL FUNCTION
The function code received in the query is not an allowable action for the server
(or slave). This may be because the function code is only applicable to newer
devices, and was not implemented in the unit selected. It could also indicate that
the server (or slave) is in the wrong state to process a request of this type, for
example because it is unconfigured and is being asked to return register values.
02 ILLEGAL DATA ADDRESS
The data address received in the query is not an allowable address for the server
(or slave). More specifically, the combination of reference number and transfer
length is invalid. For a controller with 100 registers, the PDU addresses the first
register as 0, and the last one as 99. If a request is submittted with a starting
register address of 96 and a quantity of registers of 4, then this request will
successfully operate (address-wise at least) on registers 96, 97, 98, 99. If a
request is submitted with a starting register address of 96 and a quantity of
registers of 5, then this request will fail with Exception Code 0x02 “Illegal Data
Address” since it attempts to operate on registers 96, 97, 98, 99 and 100, and
there is no register with address 100.
03 ILLEGAL DATA VALUE
A value contained in the query data field is not an allowable value for server (or
slave). This indicates a fault in the structure of the remainder of a complex
request, such as that the implied length is incorrect. It specifically does NOT
mean that a data item submitted for storage in a register has a value outside the
expectation of the application program, since the MODBUS protocol is unaware of
the significance of any particular value of any particular register.
04 SLAVE DEVICE FAILURE An unrecoverable error occurred while the server (or slave) was attempting to
perform the requested action.
05 ACKNOWLEDGE
Specialized use in conjunction with programming commands. The server (or
slave) has accepted the request and is processing it, but a long duration of time
will be required to do so. This response is returned to prevent a timeout error from
occurring in the client (or master). The client (or master) can next issue a Poll
Program Complete message to determine if processing is completed.
06 SLAVE DEVICE BUSY
Specialized use in conjunction with programming commands. The server (or
slave) is engaged in processing a long -- duration program command. The client
(or master) should re-transmit the message later when the server (or slave) is free.
08 MEMORY PARITY ERROR
Specialized use in conjuction with function codes 20 and 21 and reference type 6,
to indicate that the extended file area failed to pass a consistency check. The
server (or slave) attempted to read record file, but detected a parity error in the
memory. The client (or master) can retry the request, but service may be required
on the server (or slave) device.
0A GATEWAY PATH UNAVAILABLE
Specialized use in conjunction with gateways, indicates that the gateway was
unable to allocate an internal communication path from the input port to the output
port for processing as the request. Usually means that the gateway is
misconfigured or overloaded.
0B GATEWAY TARGET DEVICE
FAILED TO RESPOND
Specialized use in conjunction with gateways, indicates that no response was
obtained from the target device. Usually means that the device is not present on
the network.
Modbus Exception Codes

7
Modbus Instructions
Primary Data Tables
Table Data Type Read / Write
Discrete Inputs Single Bit Read Only
Coils Single Bit Read / Write
Input Registers 16-Bit Word Read Only
Holding Registers 16 Bit Word Read / Write
SYNC Boiler Memory Map
Coils
Address Description Default Unit Min. Max. Resolution
00001 Boiler Enable / Room Thermostat 1 / Stage 1 01=ON / 0=OFF 0 1 1
00005 Tank Thermostat 01=ON / 0=OFF 0 1 1
Discrete Inputs
10001 Manual Reset High Limit 1 01=ON / 0=OFF 0 1 1
10002 Flow Switch 1 01=ON / 0=OFF 0 1 1
10003 Gas Pressure Switch 1 01=ON / 0=OFF 0 1 1
10004 Louver Proving Switch 1 01=ON / 0=OFF 0 1 1
10005 Air Pressure Switch / Flap Valve 1 01=ON / 0=OFF 0 1 1
10006 Blocked Drain Switch 1 01=ON / 0=OFF 0 1 1
10007 Auto Reset High Limit 1 01=ON / 0=OFF 0 1 1
10008 Flame 1 01=ON / 0=OFF 0 1 1
10009 Enable / Room Thermostat 1 / Stage 1 01=ON / 0=OFF 0 1 1
10010 Tank Thermostat 01=ON / 0=OFF 0 1 1
10017 Manual Reset High Limit 2 01=ON / 0=OFF 0 1 1
10018 Flow Switch 2 01=ON / 0=OFF 0 1 1
10019 Gas Pressure Switch 2 01=ON / 0=OFF 0 1 1
10020 Louver Proving Switch 2 01=ON / 0=OFF 0 1 1
10021 Air Pressure Switch / Flap Valve 2 01=ON / 0=OFF 0 1 1
10022 Blocked Drain Switch 2 01=ON / 0=OFF 0 1 1
10023 Flame 2 01=ON / 0=OFF 0 1 1
10033 Run-time Contacts 01=ON / 0=OFF 0 1 1
10034 Alarm Contacts 1 01=ON / 0=OFF 0 1 1
10035 CH Pump 1 01=ON / 0=OFF 0 1 1
10036 DHW Pump 1 01=ON / 0=OFF 0 1 1
10038 Gas Valve 1 01=ON / 0=OFF 0 1 1
10039 System Pump 01=ON / 0=OFF 0 1 1
10041 Run-time Contacts 2 01=ON / 0=OFF 0 1 1
10042 Alarm Contacts 2 01=ON / 0=OFF 0 1 1
10043 CH Pump 2 01=ON / 0=OFF 0 1 1
10046 Gas Valve 2 01=ON / 0=OFF 0 1 1
3 Memory Map

8
Modbus Instructions
Input Registers
Address Description Default Unit Min. Max. Resolution
30001 Discrete Inputs 1 - 16 0 NA 0 65535 1
30002 Discrete Inputs 17 - 32 0 NA 0 65535 1
30003 Discrete Inputs 33 - 48 0 NA 0 65535 1
30004 System / Cascade Setpoint 0Degrees Celsius 0 130 0,5
30006 Cascade Total Power 0 % 100 800 1
30007 Cascade Current Power 0 % 0 800 1
30008 Outlet Setpoint 1 0Degrees Celsius 0 130 0,5
30009 Outlet Temperature 1 0Degrees Celsius 0 130 0,1
30010 Inlet Temperature 1 0Degrees Celsius -20 130 0,1
30011 Flue Temperature 1 0Degrees Celsius -20 130 0,1
30012 Firing Rate 1 0 % 0 100 1
30014 Boiler 1 Status Code 0 NA 0 65535 1
30015 Boiler 1 Blocking Code 0 NA 0 65535 1
30016 Boiler 1 Lockout Code 0 NA 0 65535 1
30017 Outlet Setpoint 2 0Degrees Celsius 0 130 0,5
30018 Outlet Temperature 2 0Degrees Celsius 0 130 0,1
30019 Inlet Temperature 2 0Degrees Celsius -20 130 0,1
30020 Flue Temperature 2 0Degrees Celsius -20 130 0,1
30021 Firing Rate 2 0 % 0 100 1
30023 Boiler 2 Status Code 0 NA 0 65535 1
30024 Boiler 2 Blocking Code 0 NA 0 65535 1
30025 Boiler 2 Lockout Code 0 NA 0 65535 1
Holding Registers
40001 Configuration 0 NA 0 65535 1
40002 Coils 0 NA 0 65535 1
40003 0-10 Volt Input / Rate Command /
Setpoint Command 0 % 0 100 1
40004 Tank Setpoint 0Degrees Celsius 0 87,5 0,5
40005 Tank Temperature 0Degrees Celsius -20 130 0,1
40006 Outdoor Temperature 0Degrees Celsius -40 60 0,1
40007 System Supply Temperature 0Degrees Celsius -20 130 0,1
SYNC Boiler Memory Map
3 Memory Map
Configuration Bits
Address 40001 contains configuration bits sent from the BAS to the boiler. These bits tell the boiler to use its own internal inputs,
or inputs from the BAS. When a bit is set to 1, the boiler will ignore the corresponding value contained internally, and expect the
BAS to write that value into the Holding Registers. The configuration bits are as follows:
Bit 4: System Supply Temperature
Bit 5: Outdoor Temperature
Bit 6: Tank Temperature
Bit 7: System Return Temperature
Bit 8 - 15: Not Used (Default = 0)
Bit 0 (LSB): Boiler Enable
Bit 1: Tank Thermostat
Bit 2: Rate Command / 10 - 10V Input / Setpoint Command
Bit 3: Tank Setpoint

9
Modbus Instructions
4 Wiring Requirements
RS-485 Communication Bus
• Maximum Length = 4000 feet
• Cable Specification = 24 AWG / A,B (twisted pair) and GND Shielded, with characteristic Impedance = 120 ohm
• Maximum Load = 32 units (32 nodes)
NOTE: Cable must be terminated with 120 ohm impedance matching resistor on each end.
Note that when the System Supply Temperature and/or the Tank Temperature are provided by the BAS, they need to be refreshed
every few seconds. This is required in order to prevent unwanted fluctuations in these temperatures. If these values are not
provided every few seconds (timeout is programmable), the boiler will revert to its own internal control. If neither of these
temperatures is provided by the BAS, but any of the other control signals are being provided, the BAS will still need to refresh
these inputs at least every 4 minutes.
Physical Wiring
Figure 4-1_Terminal Strip Connections
1 ALARM
LBL20052 REV B
30 SHIELD GND
MOD BUS
0 - 10V INPUT
2 CONTACTS
3 RUN TIME
4 CONTACTS 5 LOUVER
6 PROVING
8 FLOW SWITCH
10 FLOW SWITCH
29 A
26 SENSOR
25 TANK
24 SENSOR
23 OUT DOOR
22 SENSOR
21 SYSTEM
20 (-)
19 (+)
18 SHIELD GND
17 B
16 A
15 SHIELD GND
14 W
13 R
11 TANK
12 THERMOSTAT
28 B
27 SHIELD GND
CASCADE
ENABLE
A BA
B
A
B
BUILDING
MANAGEMENT
SYSTEM LOUVER
PROVING
SWITCH
TANK
THERMOSTAT
ENABLING DEVICE
SYSTEM SENSOR
OUTDOOR SENSOR TANK SENSOR
SHIELD
SHIELD
FROM PREVIOUS BOILER TO NEXT BOILER
SHIELD
HEAT EXCHANGER 2 FLOW SWITCH
HEAT EXCHANGER 1 FLOW SWITCH
A
B
SHIELD
MODBUS COMMUNICATION BUS
TO NEXT BOILER
9 HEX 1
7 HEX 2

10
4 Wiring Requirements
Figure 4-2_Control Inputs
GAS PRESSURE SWITCH
ROOM THERMOSTAT /
ZONE CONTROL
FLOW SWITCH
SYSTEM SENSOR
OUTDOOR SENSOR
SEQUENCER / BUILDING
MANAGEMENT SYSTEM
LOW VOLTAGE
CONNECTION
BOARD
HEAT EXCHANGER 1 /
HEAT EXCHANGER 2 INLET
TEMPERATURE SENSOR
HEAT EXCHANGER 1 /
HEAT EXCHANGER 2 OUTLET
TEMPERATURE SENSOR
HEAT EXCHANGER 1 /
HEAT EXCHANGER 2 FLUE GAS SENSOR
HEAT EXCHANGER 1 /
HEAT EXCHANGER 2 HIGH LIMIT SENSOR
FLAME SENSOR
LOW WATER CUTOFF
BLOCKED DRAIN SWITCH
TOUCH PANEL
INTERFACE
PC INTERFACE
SECONDARY
SMART TOUCH
CONTROL MODULE
PRIMARY
SMART TOUCH
CONTROL MODULE
HW TANK SENSOR
HW THERMOSTAT
TOUCH DISPLAY
MODBUS COMMUNICATION
BOARD
Modbus Instructions

11
4 Wiring Requirements (continued)
Figure 4-3_Control Outputs
LOW VOLTAGE
CONNECTION
BOARD PRIMARY
CONTROL MODULE
ALARM BELL
RUN TIME CONTACTS
SEQUENCER / BUILDING
MANAGEMENT SYSTEM
HEAT EXCHANGER 1 /
HEAT EXCHANGER 2
BOILER PUMP
SYSTEM PUMP
HW PUMP
IGNITOR
BLOWER
GAS VALVE
PC INTERFACE
SECONDARY
SMART TOUCH
CONTROL MODULE
TOUCH PANEL
INTERFACE
TOUCH DISPLAY
SMART TOUCH
Modbus Instructions

12
4 Wiring Requirements
Figure 4-4_Control Location
CONTROLLER 1
CONTROLLER 2
MODBUS
COMMUNICATION
BOARD (MTR01)
HEAT EXCHANGER 1
HEAT EXCHANGER 2
Modbus Instructions
Typical Boiler System Wiring
Cascade Daisy Chain Connection
Modbus RS485 Communication Bus
Modbus RS485 Port on Gateway orBuildingSystem
Physical Configuration: Cascade without Individual Monitoring

13
4 Wiring Requirements (continued)
Modbus RS485 Communication Bus
Modbus RS485 Port on Gateway orBuildingSystem
Physical Configuration: Direct Control
Cascade Daisy Chain Connection
Modbus RS485 Communication Bus
Modbus RS485 Port on Gateway orBuildingSystem
Physical Configuration: Cascade with individual Monitoring
Modbus Instructions

14
5 Unit Operation
Unit Operation with Modbus Communications
To control a SYNC boiler through a Building Management System communicating through Modbus, the SYNC Demand
Configuration must be set to a value of 4, 5, or 6. These configurations allow different control points for a variety of applications.
The configuration can be set by selecting Main>>Setup>>Service/Setup>>Demand Config.
Holding Registers Definition Bit Value (HEX) Action
40001 Configuration 00 01 Set Configuration to read 40002
40002 Coils 00 01 Enables unit (00 00 disables unit)
NOTE: To ensure proper operation re-send the configuration bits to holding register 40001 prior to issuing a command.
The SYNC boiler is equipped with a Modbus communication timer. This timer is programmable from 0 - 120 seconds. The timer
can be programmed from the Modbus Setup Menu by selecting Main>>Setup>>BMS>>Modbus Timeout. The purpose of the
timer is to ensure proper temperature data is communicated to the boiler in a timely manner. Additionally, it will provide for fail
safe operation should Modbus communication be lost. This timer will cause the unit to revert back to internal unit controls
should the Modbus communication be interrupted longer than the Modbus timer. The timer is reset every time a Modbus write
command is received with updated temperatures or commands. It is the recommendation of Lochinvar that this timer be set to
the shortest value possible.
When controlling a SYNC boiler through a Building Automation System (BAS), it is very important to ensure that the correct
configuration bits are sent to holding register 40001, and that the correct data and enable signals are sent to holding registers
40002 - 40007, per the demand configuration.
Demand Configuration 4
In this configuration the unit is controlled by setting the setpoints locally on the boiler and providing an enable signal through
Modbus communications.
All sensors and limiting devices should be hardwired to the terminal strip on the back of the unit excluding the thermostat enable
and tank thermostat enable signal. These signals will be sent to the unit via Modbus.
The holding registers will need to be set as follows:
Figure 5-1_Setup Screen
Modbus Instructions

15
5 Unit Operation (continued)
Demand Configuration 6
In this configuration the unit is controlled by setting the modulation setpoint from 0 - 100%.
Rate command will be 0 - 100% of the modulation range.
All sensors and limiting devices should be hardwired to the terminal strip on the back of the unit excluding the 0 - 10Vdc signal.
This signal will be sent to the unit via Modbus.
The holding registers will need to be set as follows:
Holding Registers Definition Bit Value (HEX) Action
40001 Configuration 00 04 Set Configuration to read 40003
40003 Rate Command 00 00 Sets Modulation %
For proper hexadecimal conversion of rate percentage, please refer to the Rate and Temperature Conversion section on page 17
of this manual.
NOTE: To ensure proper operation re-send the configuration bits to holding register 40001 prior to issuing a command.
Hot Water Generation
Hot water generation can be accomplished with one of two methods when a SYNC boiler is connected to a BAS system, DHW
with direct control, and DHW with remote control.
DHW with direct control:
This is the typical installation with a hot water generator in close proximity to the boiler with the tank thermostat, or tank
temperature sensor, wired to the terminal strip of the unit.
Demand Configuration 5
In this configuration the unit is controlled by providing an enable signal and a rate command through Modbus communications.
The rate command will be 0 - 100% of modulation.
All sensors and limiting devices should be hardwired to the terminal strip on the back of the unit excluding the thermostat enable
and tank thermostat enable signal. These signals will be sent to the unit via Modbus.
The holding registers will need to be set as follows:
Holding Registers Definition Bit Value (HEX) Action
40001 Configuration 00 05 Set Configuration to read 40002 & 3
40002 Coils 00 01 Enables unit (00 00 disables unit)
40003 Rate Command 00 ## Sets Modulation % or Setpoint
NOTE: To ensure proper operation re-send the configuration bits to holding register 40001 prior to issuing a command.
For proper hexadecimal conversion of rate percentage, please refer to the Rate and Temperature Conversion section on page 17
of this manual.
Modbus Instructions

16
5 Unit Operation
Cascade
In order to operate the SYNC boiler in Cascade with Modbus
communications, configure the leader boiler per the demand
configurations in this manual. Connect the remaining boilers
in the cascade through the normal cascade communications
wiring. Cascade control can then be accomplished
automatically through the leader boiler.
Please note that with Modbus communication connected to
only the leader boiler, total Cascade information can be seen
through the communications link. If you wish to see all the
individual temperatures of each unit in the Cascade, each unit
will have to have a Modbus communication board. However,
each unit can be monitored without the need to control each
one individually.
DHW with remote control:
This installation may or may not have the hot water generator in close proximity to the boiler. Its sensors and thermostat values
are only available through the Modbus communication bus.
To ensure that the SYNC boiler can properly respond to a call for hot water generation the following holding registers must be
set in addition to other commands:
Holding Registers Definition Bit Value (HEX) Action
40001 Configuration 00 4A Set Configuration to read 40002, 4 & 5
40002 Coils 00 08 Enables Tank Tstat (00 00 disables unit)
40004 Tank Setpoint 0# ## Sets Setpoint
40005 Tank Temperature 0# ## Passes tank temp from remote sensor
For proper hexadecimal conversion of rate percentage, please refer to the Rate and Temperature Conversion section on page 17
of this manual.
NOTE: To ensure proper operation re-send the configuration bits to holding register 40001 prior to issuing a command.
Modbus Instructions
Monitoring Only
Any SYNC boiler can be equipped with the Modbus
communication board and then be set up to operate with its
own internal controls. If necessary, Modbus can be configured
as a monitoring device by selecting demand configurations 1 -
3, and polling the Modbus board for the read only variables.

17
Temperature
The SYNC boiler passes temperature data in degrees Celsius.
Also, to accommodate decimal places the decimal value must be
divided by 10.
Here are the conversions to and from Celsius:
Tc= (5/9) * (Tf-32) Tf= (9/5) * Tc+32
Example:
Outdoor temperature from remote sensor on BAS System = 80°F
80°F = 26.7°C
Data that needs to be transmitted is 26.7 * 10 = 267
Decimal Binary HEX
267 100001011 10B
Outlet temperature from unit sensor = 155°F
155°F = 68.3°C
Data transmitted from unit in HEX = 2AB = 683
683 ÷ 10 = 68.3 (°C)
Decimal Binary HEX
683 1010101011 2AB
Modbus Instructions
Rate and Temperature Conversions:
Rate
When issuing a rate command the rate can be communicated
as percent modulation or a desired setpoint, depending on the
setting of the BMS Type in the BMS Setup Menu.
The proper data format for the modulation percentage is the
direct conversion to hexadecimal. This conversion can be
accomplished through online number based converters or
some scientific calculators.
For Example:
To send a desired setpoint, the hexadecimal value must be
determined through linear interpolation of programmable
parameters on the BMS Setup Menu:
- BMS temperature set-point at low analog input
- BMS temperature set-point at high analog input
These variables set the temperature values corresponding to
the minimum and maximum voltage settings of the 0-10 volt
signal. The defaults are as follows:
Rate % HEX
0 00
20 14
45 2D
60 3C
80 50
95 5F
100 64
PARAMETER
DEFAULT
VALUES DEFAULT
Deg C Deg F Voltages
BMS temperature setpoint at
low analog input 21 69.8 2
BMS temperature setpoint at
high analog input 82 179.6 10
For Example:
Send a setpoint of 110°F.
The formula to use for the interpolation is:
Rate Command =
(Desired Setpoint – BMS Temp at Low Analog Input) (High
Voltage-Low Voltage) + Low Voltage
(BMS Temp at High Analog Input – BMS Temp at Low
Analog Input)
From the default values:
Desired Setpoint = 110
BMS Temp at Low Analog Input =68
BMS Temp at High Analog=158
High Voltage =10
Low Voltage = 2
[(110-69.8)(10-2)/(179.6-69.8)] + 2 = 4.92 Volts
(4.92/10) x 100 = 49.2
49 = 31 Hexadecimal
A value of [00][31] in hexadecimal would be written to Holding
register 40003 to issue a command for a 110°F setpoint.
5 Unit Operation (continued)

18
6 Troubleshooting
Should you encounter problems communicating over
Modbus, the following items should be checked in this order:
1. Physical Layer
2. Communications Configuration and Port Settings
3. Modbus Error Codes
4. Unit Status / Blocking / Lockout Codes
Physical Layer
1. Check that all components have power (Boiler, Gateway,
BAS Master)
2. Check all wire lengths. Are any drops too long?
3. Check proper shield grounding
4. Check A, B terminal connections
5. Check for Terminating Resistors (120 ohms)
6. Check for broken wires
Communications
1. Check Dip Switch Configuration of MTR-01 Board
2. Check Baud Rate (9600, 19200)
3. Check Parity
4. Check Slave ID
5. Check Port Setting on Master, Gateway, and Computers
Modbus Error Codes
1. Check Modbus communication for error codes (see page
6 for Modbus Exception Codes)
2. Check Modbus PDU
3. Check Slave ID
4. Check Modbus Command
5. Check Configuration bits for Holding Register 40001
6. Check Commands and data for Holding Registers
40002 - 40007
Unit Status Codes
See Codes in this section
Boiler Status
The SYNC boiler displays a boiler state code on the Building
Screen to help aid in troubleshooting. The boiler state
indicates what the boiler is actually doing. This state should
be compared to the command issued and what is expected. If
the boiler state does not agree with the command issued,
check communication and configuration.
Status Codes (Input Registers 30014 and 30023)
2 = Heat Demand blocked due to high absolute outlet
temperature
3 = Heat Demand blocked due to high absolute flue
temperature
4 = Heat Demand blocked due to high absolute Delta T
(Outlet - Inlet)
8 = Heat Demand blocked due to Low 24 VAC
9 = Outdoor shutdown
10 = Block due to switch OFF boiler (ON/OFF of Display)
12 = Block due to no correct communication Cascade
16 = Service function
19 = DHW function Storage Tank
21 = SH function Heat demand from Room Thermostat
22 = SH function Heat demand from Boiler Management
System
23 = SH function Heat demand from Cascade
30 = Heat demand activated by Freeze Protection
32 = DHW Pump Delay
33 = SH Pump Delay
34 = No heat function (after pump delay)
40 = Lockout
32764 = Busy with updating status
32765 = DHW blocked due to no present tank sensor
32766 = Burner control(s) manually shut down
32767 = Code not present
Blocking Codes (Input Registers 30015 and 30024)
0 = No blocking _> is divided into sub blockings
1 = SH blocking
2 = Blocking Due to Low 24 VAC Supply
3 = Blocking due to General block
4 = Blocking MRHL is open
5 = Blocking due to Switched OFF boiler (Display ENTER
switch)
6 = Blocking due to wrong communication of Cascade
7 = Blocking due to High Delta
8 = Blocking due to High Flue Temperature
9 = Blocking due to High Outlet Temperature
10 = Service blocking
12 = DHW blocking high outlet temperature (DHW configured
as storage tank)
13 = Blocking anti-cycling time
14 = Storage Tank demand Blocked due to Fan problems
15 = No system sensor connected and leader control present
16 = Limit fan speed due to high outlet temperature
17 = Fan min decreased due to low flame current
18 = Limit max fan speed due to high Delta T
19 = Limit max fan speed due to high flue temp
32767 = Code not present
Modbus Instructions

19
6 Troubleshooting (continued)
Lockout Codes (Input Registers 30016 and 30025)
161 = EEPROM code Parameters not Re-Programmed by
Lochinvar
164 = EEPROM code No Reset Allowed (> 15 minutes)
166 = EEPROM code Auto Reset High Limit
167 = EEPROM code Blocked Drain
168 = EEPROM code Louver Proving
169 = EEPROM code Gas Pressure Sw
170 = EEPROM code Flow Switch
177 = Sensor 3 short (Flue Sensor)
178 = Sensor 3 open (Flue Sensor)
179 = Sensor 2 short (Inlet Sensor)
180 = Sensor 2 open (Inlet Sensor)
192 = Sensor 1 short (Outlet Sensor)
193 = Sensor 1 open (Outlet Sensor)
204 = CRC EEPROM failed
205 = EEPROM programmed (display shows “PP”)
206 = EEPROM error in programming
207 = Write error EEPROM
229 = EEPROM code Watch Dog
230 = EEPROM code fan low (should be high)
231 = EEPROM code fan high (should be low)
232 = EEPROM code no flame when running
233 = EEPROM code no flame after ignition
234 = EEPROM code simultaneous output APS and Fan
235 = EEPROM code APS active not Closed
236 = EEPROM code APS active not Open
237 = EEPROM code flame out of sequence
239 = EEPROM code when gas valve relay test fails
240 = EEPROM code MRHL
32767 = Code not present
Modbus Instructions
Installation / Replacement Procedure
1
3
2
UNPLUG THREE (3) WIRE HARNESSES
Figure 6-1_MTR01 Control Board
1. Turn OFF the main electrical power to the appliance.
2. Turn OFF the main manual gas shutoff to the appliance.
3. Unplug the three (3) wire harnesses on the MTR01 control
board (see FIG. 6-1).
4. Unscrew the four (4) mounting nuts on the MTR01 control
board and set aside. Remove the MTR01 control board (see
FIG. 6-2).
5. Replace / install the new MTR01 control board.
6. Replace the four (4) mounting nuts removed in Step 4.
7. Reconnect all three (3) wire harnesses unplugged in Step 3.
8. Turn on the main electrical power and the main manual gas
shutoff to the appliance.
9. Configure the MTR01 control board and unit controls per
this manual and resume operation.
UNSCREW THE FOUR (4)
MOUNTING NUTS ON THE MODBUS
CONTROL BOARD (MTR01) AND SET
ASIDE TO SECURE THE
NEW MTR01 CONTROL BOARD
TO THE CONTROL PANEL
Figure 6-2_Control Panel w/MTR01 Control Board

20
Modbus Instructions
BOX DEPICTS
OPTIONAL ITEMS
LADDER DIAGRAM
LBL20058 REV E
CONTROL
MODULE 2
X5-3
X2-1
GAS VALVE
GAS VALVE
RELAY
X5-5
X5-13
X5-6
X5-12
1
2
4
5
TR1
X1-7
FLAME ROD
SPARK
ROD
120 VAC
LOW VOLTAGE
HIGH VOLTAGE
CAUTION HIGH VOLTAGE SPARK LEAD
BLOWER
X2-2
NOTES:
1. Where possible, switches are shown without utilities (gas, water or
electricity) connected to the unit. As such, actual switch states may
vary from those shown on diagrams depending upon whether utilities
are connected or a fault condition is present.
2. See wiring diagram for additional notes.
AIR PRESSURE
SWITCH
CONTROL
MODULE 1
X5-3
X2-1
GAS VALVE
GAS VALVE
RELAY
X5-5
X5-13
X5-6
X5-12
1
2
4
5
TR1
X1-7
FLAME ROD
SPARK
ROD
CAUTION HIGH VOLTAGE SPARK LEAD
BLOWER
X2-2
FLAP
VALV E
AIR PRESSURE
SWITCH
FLAP
VALV E
X5-7 24V X5-7
24V
X5-4
X5-4
INLET
SENSOR
INLET
SENSOR
OUTLET
SENSOR
FLUE
SENSOR
OUTLET
SENSOR
FLUE
SENSOR
HI-LIMIT HI-LIMIT
X5-2
X5-1
X5-8
X5-14
AUTO RESET
HIGH LIMIT AUTO RESET
HIGH LIMIT
X5-9
BLOCKED
DRAIN
X5-8
X5-1
X5-9
X5-2
CN3
RS485
SHIELD
SHIELD
CASCADE
TANK
SENSOR
OUTDOOR
SENSOR
SYSTEM
SENSOR
EXTERNAL
CONTROL
RS485
SHIELD
SHIELD
MOD BUS
CN3-16
CN3-15
CN3-14
CN3-13
CN3-12
CN3-11
CN3-10
CN3-9
CN3-8
CN3-7
CN3-6
CN3-5
CN3-4
CN3-3
CN3-2
CN3-1
CONNECTION BOARD
+
-
10VDC
MOD BUS
KIT
CONTROL
MODULE 1
CONTROL
MODULE 2
X4 X4
CN4-3
CN4-1
CN4-2
CN4-4
CN4-6
CN4-5
CN4-8
CN4-7
CN4-9
CN4-10
4
X5-10
X5-10
LOUVER
RELAY 1
LOUVER
RELAY 2
X8 X8
X5-7
X6-8
X6-8
X5-14
X4-3
X4-1
X4-2
X4-4
X4-3
X4-1
X4-2
X4-4
X4-6
X4-5
X4-8
X4-7
X4-9
X4-10
7 Diagrams
Figure 7-1 Ladder Diagram_Part 1