Lochinvar 1.5-3.5 User Manual

FB-MODB Rev A

MODBUS COMMUNICATION

INSTRUCTIONS

Crest Models: 1.5 - 3.5

 WARNING

This manual must only be used by a qualiﬁ ed 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.

Save this manual for future reference.

Contents

1. INTRODUCTION

Deﬁ nitions .................................................................... 2

Minimum System Requirements .................................. 2

2. CONFIGURATION

Addressing ................................................................... 3

Timing Speciﬁ cations ................................................... 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

Crest Boiler Memory Map ............................................7-8

Input Registers ........................................................ 8

Holding Registers .................................................... 8

Conﬁ guration 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 ........................................... 18-21

7. DIAGRAMS

Ladder Diagram ............................................................ 22

Wiring Diagram ............................................................ 23

Revision Notes ................................................... Back Cover

1 Introduction

The information contained in this manual provides general guidelines for the implementation of ModBus communication with the Lochinvar Crest boiler.

All ModBus networks are implemented utilizing a master-slave arrangement where all Crest boilers are slaves and the master is a building automation system capable of communicating over a RS-485 serial connection.

Deﬁ nitions

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 Signiﬁ cant Byte

ModBus® A serial, half-duplex data transmission protocol developed by AEG Modicon MSB Most Signiﬁ cant Byte

RS232

RS485 A standard for serial transmission of data based on the RS-485 Standard

A standard for serial, full-duplex (FDX) transmission of data based on the RS232 Standard

RTU Remote Terminal Unit

Minimum System Requirements

• BAS system or computer with a serial or USB port with a converter to RS-485.

Shielded twisted pair communication cable.

ModBus Instructions

2 Conﬁ guration

The ModBus communication board is equipped with a set of ten dip switches that are used to set the board conﬁ guration (address, baud rate, and parity settings). The ﬁ rst eight are used to set the address of each board. The ninth is used to set the baud rate. The tenth is used to set the parity.

Figure 2-1_ModBus Communication Board

DIP SWITCHES

LED’S

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

2 Conﬁ guration

ModBus Instructions

Timing Speciﬁ cations

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 MENU>>SETUP>>MODBUS 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 = Even 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 conﬁ gured 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 efﬁ cient, 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 bright, 1 second dim 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.

2 Conﬁ guration (continued)

ModBus Function Set

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

11 0B Diagnostic - Return Bus Message Count

Diagnostic - Clear Counters and Diagnostic Registers

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

2 Conﬁ guration

ModBus Exception Codes

MODBUS Exception Codes

Code Name Meaning

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

01 ILLEGAL FUNCTION

02 ILLEGAL DATA ADDRESS

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 unconﬁ gured and is being asked to return register values.

The data address received in the query is not an allowable address for the server (or slave). More speciﬁ cally, the combination of reference number and transfer length is invalid. For a controller with 100 registers, the PDU addresses the ﬁ rst 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.

ModBus Instructions

03 ILLEGAL DATA VALUE

04 SLAVE DEVICE FAILURE

05 ACKNOWLEDGE

06 SLAVE DEVICE BUSY

08 MEMORY PARITY ERROR

A value contained in the query data ﬁ eld 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 speciﬁ cally 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 signiﬁ cance of any particular value of any particular register.

An unrecoverable error occurred while the server (or slave) was attempting to perform the requested action.

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.

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.

Specialized use in conjuction with function codes 20 and 21 and reference type 6, to indicate that the extended ﬁ le area failed to pass a consistency check. The server (or slave) attempted to read record ﬁ le, 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

GATEWAY TARGET DEVICE

FAILED TO RESPOND

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 misconﬁ gured or overloaded.

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 Instructions

3 Memory Map

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

Crest Boiler Memory Map

Coils

Address Description Default Unit Min. Max. Resolution

00001 Boiler Enable 0 1=ON / 0=OFF 0 1 1 00005 Tank Thermostat 0 1=ON / 0=OFF 0 1 1

Discrete Inputs

10001 Manual Reset High Limit 0 1=ON / 0=OFF 0 1 1 10002 Flow Switch 0 1=ON / 0=OFF 0 1 1 10003 Gas Pressure Switch 0 1=ON / 0=OFF 0 1 1 10004 Louver Proving Switch 0 1=ON / 0=OFF 0 1 1 10005 Blower Proving Switch 1 0 1=ON / 0=OFF 0 1 1 10006 Blocked Drain Switch 0 1=ON / 0=OFF 0 1 1

10008 Flame 1 0 1=ON / 0=OFF 0 1 1 10009 Enable 0 1=ON / 0=OFF 0 1 1 10010 Tank Thermostat 0 1=ON / 0=OFF 0 1 1 10011 Blocked Flue 0 1=ON / 0=OFF 0 1 1 10013 Blower Proving Switch 2 0 1=ON / 0=OFF 0 1 1 10021 Flue Damper Proving Switch 0 1=ON / 0=OFF 0 1 1 10023 Flame 2 0 1=ON / 0=OFF 0 1 1

10033 Run-time Contacts 0 1=ON / 0=OFF 0 1 1 10034 Alarm Contacts 0 1=ON / 0=OFF 0 1 1 10035 SH Pump 0 1=ON / 0=OFF 0 1 1 10036 DHW Pump 0 1=ON / 0=OFF 0 1 1 10038 Gas Valve 1 0 1=ON / 0=OFF 0 1 1 10039 System Pump 0 1=ON / 0=OFF 0 1 1

10044 Vent Damper Relay 0 1=ON / 0=OFF 0 1 1 10046 Gas Valve 2 0 1=ON / 0=OFF 0 1 1 10049 Blower #1 Power 0 1=ON / 0=OFF 0 1 1 10050 Blower #2 Power 0 1=ON / 0=OFF 0 1 1 10051 Spark Igniter 0 1=ON / 0=OFF 0 1 1

ModBus Instructions

3 Memory Map

Crest Boiler Memory Map

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 0 Degrees Celsius 0 130 0,5 30005 System Pump Speed 0 % 0 100 1 30006 Cascade Total Power 0 % 100 800 1 30007 Cascade Current Power 0 % 0 800 1 30008 Outlet Setpoint 0 Degrees Celsius 0 130 0,5 30009 Outlet Temperature 0 Degrees Celsius 0 130 0,1 30010 Inlet Temperature 0 Degrees Celsius -20 130 0,1 30011 Flue Temperature 0 Degrees Celsius -20 130 0,1 30012 Firing Rate 0 % 0 100 1 30013 Boiler Pump Speed 0 % 0 100 1 30014 Boiler Status Code 0 NA 0 65535 1 30015 Boiler Blocking Code 0 NA 0 65535 1 30016 Boiler Lockout Code 0 NA 0 65535 1

Holding Registers

40001 Conﬁ guration 0 NA 0 65535 1 40002 Coils 0 NA 0 65535 1

40003 40004 Tank Setpoint 0 Degrees Celsius 0 87,5 0,5

40005 Tank Temperature 0 Degrees Celsius -20 130 0,1 40006 Outdoor Temperature 0 Degrees Celsius -40 60 0,1 40007 System Supply Temperature 0 Degrees Celsius -20 130 0,1 40008 System Return Temperature 0 Degrees Celsius -20 130 0,1

0-10 Volt Input / Rate Command / Setpoint Command

0 % 0 100 1

Conﬁ guration Bits

Address 40001 contains conﬁ guration 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 conﬁ guration bits are as follows:

Bit 0 (LSB): Boiler Enable Bit 1: Tank Thermostat Bit 2: Rate Command / 10 - 10V Input / Setpoint Command Bit 3: Tank Setpoint

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)

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