EngA ENGINEERED AIR base - Dj;Large Sh(X) Indirect Fired; Basic Operation; Dj; CD-XM Timing

base A
19
IOM74 November 2020 R105
DJ/LARGE SH(X) INDIRECT FIRED
For indirect fired equipment with DJ (E, S, X) style burners up to size 140. Large sizes (120-650) of SH(X) use
the DJ burner.
BASIC OPERATION
On a call for heating the combustion blower will be enabled to full speed to prepurge the heat exchanger.
Once the prepurge time has elapsed the combustion blower speed will reduce to ignition speed and then
enable the ignition control to start and prove pilot flame, then open the main safety valve (SSOV). After a
time delay the base will disable the pilot valve. The burner is allowed to operate to maintain the requested
discharge air temperature from the base by modulating the control valve and the combustion blower speed. If
heating is not required the burner will be disabled and the combustion blower will enter a post purge time, and
then shut down.
The base can control either a Maxitrol magnetic style modulating valve or an actuator and valve.
Combustion air blower modulation is controlled by the CD-XM expansion module.
DJ / CD-XM TIMING
Prepurge
60 seconds
Post purge
5 minutes
Flame failure
15 seconds lockout on ignition control and 60 seconds on burner
Pilot opening time
8 seconds
Open combustion air
proving
30 seconds
RPM out of range
60 seconds
Improper gas valve wiring
5
seconds
Blocked condensate
5 minutes
Blocked flue
10 seconds trip and 1 minute to alarm
Heat exchanger cool down
90 seconds if the discharge air is above 50° (10°C), else none.
Heat exchanger warm up
fan delay
75 seconds if ambient air is less than 40°F (4°C) and discharge temperature less
than 90°F (32°C), else no warm up.
Burner cool down
90 seconds if the burner has been on for more than 30 seconds, else no burner
cool down