Boiler Control Instruction & Operation Manual, Rev 1
Page
26
of 64
Installation
Energy Management Interface
Table 8: Modbus Signal List (continued)
Modbus
Register
Protocol
Name
Description
Read (R)/
Write (W)
10,817
Outdoor
Temperature
Building Automation may send the controller the
outdoor air temperature. Use this register to change
the outdoor temperature. When this register is not
written every
“Modbus Command Time Out” parameter
seconds (default 30 seconds), temperature is set to
bad data quality and outdoor air reset is set back to
local setpoint.
valid range -40 F to 302 F
W
Burner
581
CH Modbus Rate
Use this register to drive individual boiler firing rates.
This register is used when firing rate control is
performed by an external building automation system.
Firing rate reverts to local control when register is not
written every
“Modbus Command Time Out” parameter
seconds (default 30 seconds),
Range is 0 to 200 % provides 0-100% firing rate.
W
8
Fan Speed
Measured
Speed of the combustion air blower in rpm
R
9
Fan Speed
Commanded
Speed of the combustion air blower in rpm
R
10
Flame signal
0.01V or 0.01
μA precision (0.00-50.00V)
R
33
Burner control state
0
Initiate
1
Standby Delay
2
Standby
3
Safe Startup
4
Prepurge - Drive to Purge Rate
5
Prepurge
– Measured Purge Time
6
Prepurge
– Drive to Lightoff Rate
7
Preignition Test
8
Preignition Time
9
Pilot Flame Establishing Period
10
Main Flame Establishing Period
11
Direct Burner Ignition
12
Run
13
Postpurge
14
Lockout
R
