15
HOLDING REGISTER 40001
DEFINITION
0 = TAKEN FROM CONTROL
1 = TAKEN FROM MODBUS
B0
Boiler enable
0/1
B1
Tank enable
0/1
B2
Rate command / 0
– 10V input / set point command (40003)
0/1
B3
DHW set point (40004)
0/1
B4
DHW temperature (40005)
0/1
B5
Outdoor temperature (40006)
0/1
B6
System supply temperature (40007)
0/1
B7
System return temperature (40008)
0/1
B8
I4 offset (40009)
0/1
B9
CH post purge (40010)
0/1
HOLDING REGISTER 40001
DEFINITION
0 = TAKEN FROM CONTROL
1 = TAKEN FROM MODBUS
B10
DHW post purge (40011)
0/1
B11
Pump 4 speed (40012)
0/1
B12
Pump 5 speed (40013)
0/1
B13
Extra 0
– 10 V output (40014)
0/1
HOLDING REGISTER 40002
DEFINITION
Coil 01 b0
Room thermostat
Coil 05 b4
Tank thermostat
Table 14
– Modbus holding registers
PART 7 - APPLIANCE OPERATION
A. APPLIANCE OPERATION WITH MODBUS COMMUNICATIONS
The appliance is equipped with a Modbus communication timer. Timeout is set for four minutes. The purpose of the timer is to ensure
proper temperature data is communicated to the appliance in a timely manner.
Additionally, the communication timer will provide fail safe operation should Modbus communication be lost. This timer will cause the
appliance to revert back to internal appliance controls should the Modbus communication be interrupted longer than the Modbus timer.
The timer resets every time a Modbus write command is received with updated temperatures or commands.
The master should update temperature registers at least once per minute, but no more than once per second.
B. EXAMPLE #1
In this configuration, the appliance is controlled by setting the set points locally on the appliance and providing an enable signal through
Modbus communications.
All sensors and limiting devices (excluding the thermostat enable and tank thermostat enable signals, which will be sent to the
appliance via Modbus) should be hardwired to the proper terminals in the appliance.
The holding registers need to be set as follows:
HOLDING REGISTERS
DEFINITION
VALUE
ACTION
40001
Configuration
00 01
Set configuration to read 40002
40002
Coils
00 01
Enables CH Demand
(00 00 disables demand)
40002
Coils
00 10
Enables DHW demand on appliance (00 00 disables demand)
40002
Coils
00 11
Enables both CH and DHW demand. DHW demand will have priority
Table 15
C. EXAMPLE #2
1. SEND FIRING RATE COMMAND FROM MASTER
In this configuration, the appliance is controlled by setting the modulation set point from 0
– 100%. Rate command will be 0 – 100% of
the modulation range. All sensors and limiting devices (excluding the 0
– 10 Vdc signal, which will be sent to the Modbus) should be
hardwired to the terminal strip on the back of the appliance.
For this command to function on Munchkin and Mod Con models, set Installer Parameter 16 at 2 and Installer Parameter 17 at 1. On
Elite models, Function 16, Optional Input must be set to 0-10 volt and Function 17 0-10 volt function must be set on Temperature.
The holding registers need to be set as follows:
