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APEX Installation, Operating, & Service Instructions APEX Installation, Operating, & Service Instructions
TROUBLESHOOTING
Modbus
Register
Protocol
Name
Description
Read (R) /
Write (W)
410034 Lockout code
Reasons for burner lockout
0 No lockout,
4 Supply high limit
5 DHW high limit
6 Stack High limit
12 Flame detected out of sequence
18 Lightoff rate proving failed
19 Purge rate proving failed
20 Invalid Safety Parameters
21 Invalid Modulation Parameter
22 Safety data verification needed
23 24 VAC voltage low/high
24 Fuel Valve Error
25 Hardware Fault
26 Internal Fault
27 Ignition Failure
R
410040 Hold code
Reason for burner hold
0 None
1 Anti short cycle
2 Boiler Safety Limit Open
3 Boiler Safety Limit Open, (ILK Off)
7 Return sensor fault
8 Supply sensor fault
9 DHW sensor fault
10 Stack sensor fault
11 Ignition failure
13 Flame rod shorted to ground
14 Delta T inlet/outlet high
15 Return temp higher than supply
16 Supply temp has risen too quickly
17 Fan speed not proved
23 24 VAC voltage low/high
25 Hardware Fault
27 Ignition Failure
R
STATISTICS
400763
Modbus command
timeout
This parameter sets the amount of time the control will wait for input from the
Building Automation System (BAS). If the BAS does not write to the following
register within the “Modbus Command timeout” seconds the following inputs are
considered invalid:
CH Modbus Stat,
CH Modbus Setpoint,
CH Sequencer Modbus Setpoint
CH Modbus Rate
range 30 – 120 Default 30 seconds
Other R/W registers should only be written when a value is needed to be
changed. Only the above listed registers are stored in non-volatile registers.
R/W
Table 10-26: Modbus Register List (continued)
10 Operation (continued)
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