HeatNet Smith Series, User Manual

Page: 54 / 82

COMMUNICATIONS HeatNet Control REV 1.38-1
Page 54
MODBUS Communications
The Smith-Series control can be controlled using Modbus commands to Enable/Disable the boiler/system. A connection to
the Console Modbus Port on the Communications board is required. The Master Boiler assumes the role of MEMBER, RTU,
192Kb, 8 bits, Even Parity, 1 stop bit, when connected to a BMS (Building Management System).
The Member Boilers should not be connected to a BMS system other than to view Read Only addresses. Refer to
http://www.smithboiler.com/ website for greater detail on communicating with Modbus, BACnet, or LonWorks protocols.
Figure 38
MODBUS Input/Output Variables (Read/Write)
Address Name Raw Data Type Scale
Description Valid
Values/Range
40001 HeatDemand 1 bit unsigned ---
Heat Demand/Request. Setting the state
member of this variable will put the boiler
in heating mode.
0 = no heat demand
1 = heat demand
40002 SetpointTimer 16 bit unsigned ---
System Setpoint Timer
The system setpoint timer and system
setpoint work in tandem to externally
control (i.e. a BMS - building management
system) the operating setpoint. The
setpoint (countdown) timer should be
loaded with a timeout value (in seconds)
prior to writing the system setpoint. When
the timer reaches zero, the control
assumes that the BMS is no longer
operating and the local setpoint (saved on
the control) is reloaded. This is a failsafe
feature used to help safeguard the system
in case of BMS failure. If the setpoint timer
is not written, a default timeout value of 60
seconds is assumed.
0 – 65535 seconds
40003 Setpoint 8 bit unsigned 1.0 System Setpoint (see SetpointTimer ) 40 - 220 °F
40004 OAResetEnable 1 bit unsigned --- Enables/Disables outdoor air reset mode.
0 = disabled
1 = enabled
40005 OARSetpoint 8 bit unsigned 1.0
Outdoor air reset setpoint. Temperature at
which boiler shuts down.
40 – 100 °F
40006 OARHighWaterTemp 8 bit unsigned 1.0
Boiler water temperature setpoint when
outdoor air temperature is at the high
outdoor air temperature setpoint
(OARHiAirTemp).
60 – 150 °F
40007 OARHighAirTemp 8 bit unsigned 1.0 High outdoor air temperature setpoint. 50 – 90 °F
40008 OARLowWaterTemp 8 bit unsigned 1.0
Header/Supply temperature setpoint when
outdoor air temperature is at the low
outdoor air temperature setpoint
(OARLoAirTemp).
70 – 220 °F
40009 OARLowAirTemp 8 bit signed 1.0 Low outdoor air temperature setpoint. -35 – 40 °F
40010 SetMonth 8 bit unsigned ---
Set real time clock – month ( see SetClock )
0 (January) - 11
(December)
40011 SetDay 8 bit unsigned --- Set real time clock – day ( see SetClock ) 1 – 31
40012 SetYear 8 bit unsigned ---
Set real time clock – year ( see SetClock )
0 – 99