8
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
0-10 Volt Input / Rate Command / Setpoint
Command
0
%
0
100
1
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
Crest Boiler Memory Map
3
Memory Map
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 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
ModBus Instructions
